Management of Individuals With Patellofemoral Pain PDF

Journal of Athletic Training 2018;53(9):820–836 doi: 10.4085/1062-6050-231-15 Ó by the National Athletic Trainers’ Association, Inc Position Statement www.natajournals.org National Athletic Trainers’ Association Position Statement: Management of In...

Journal of Athletic Training doi: 10.4085/1062-6050-231-15 Ó by the National Athletic Trainers’ Association, Inc www.natajournals.org National Athletic Trainers’ Association Position Statement: Management of Individuals With Patellofemoral Pain Lori A. Bolgla, PhD, PT, MAcc, ATC*; Michelle C. Boling, PhD, LAT, ATC†; Kimberly L. Mace, DAT, ATC‡; Michael J. DiStefano, MA, ATC, PES, CSCS§; Donald C. Fithian, MDjj; Christopher M. Powers, PhD, PT, FACSM, FAPTA¶ *Department of Physical Therapy, Augusta University, GA; †Department of Clinical and Applied Movement Sciences, University of North Florida, Jacksonville; ‡Sargent University, MA; §Select Physical Therapy, Storrs, Orthopaedic Medical Group, La Jolla, CA; ¶Department of Biokinesiology and Physical Therapy, University California, Los Angeles Objective: To present recommendations for athletic trainers and other health care providers regarding the identification of risk factors for and management of individuals with patellofem- oral pain (PFP). Background: Patellofemoral pain is one of the most common knee diagnoses; however, this condition continues to be one of the most challenging to manage. Recent evidence has suggested that certain risk factors may contribute to the development of PFP. Early identification of risk allow clinicians to develop and implement programs aimed at reducing the incidence of this condition. To date, clinicians have P atellofemoral pain (PFP) is one of the most common knee conditions in patients presenting to orthopaedic practices.1–4 Although frequently seen in a wide range of populations, PFP is particularly prevalent in younger people who are physically active.5–7 In addition, females are reported to be at higher risk for the development of PFP than males.7,8 The signiﬁcance of PFP is highlighted by the fact that as many as 70% to 90% of individuals with this condition have recurrent or chronic symptoms.1,3,9,10 Interventions for PFP have shown positive short-term outcomes, but long- term clinical outcomes are less compelling.1,9,11,12 The apparent lack of long-term success in treating this condition may be due to an incomplete understanding of the underlying factors that contribute to its development. Due to its multifactorial causes, the treatment of PFP is complex 820 Volume 53 Number 9 September 2018 For the practicing clinician, any recommendation with an A grade warrants attention and should be inherent to clinical practice. Less research supports recommendations with grade B or C; these should be discussed by the sports medicine staff. Grade B recommendations are based on inconsistent or limited controlled research outcomes. Grade C recommendations should be considered as expert guidance despite limited research support. RECOMMENDATIONS Risk Factors (Based on Prospective Studies) 1. Hip adduction and internal rotation during dynamic tasks such as running and landing from a jump are risk factors for the development of PFP.5,15 SOR: B 2. Increased knee-abduction impulses and moments during running and drop landings are risk factors for the development of PFP.16,17 SOR: B 3. Novice runners who developed PFP generated greater vertical peak force to the lateral heel and second and third metatarsals. Military recruits who developed PFP walked with greater lateral foot pressure.18 SOR: B 4. Reduced isometric hip-abductor, external-rotator, hip-extensor strength are not likely risk factors development of PFP.19,20 SOR: B 5. Quadriceps weakness is a risk factor for the develop- ment of PFP.21,22 SOR: B 6. Delayed activation of the vastus medialis obliquus (VMO) relative to the vastus lateralis (VL), as identiﬁed with a patellar tendon tap or voluntary tasks (eg, rocking back on the heels), can contribute to the onset of PFP.23,24 SOR: C 7. Static measures, such as the quadriceps angle (Q- angle), foot posture index, lower leg-heel alignment, and heel-to-forefoot alignment, are not predictors of PFP development.5,24–26 SOR: B 8. Individuals with quadriceps tightness and decreased vertical-jump performance have developed PFP.24 SOR: B Pain and Functional Outcome Measures 9. Clinicians should use a 10-cm visual analog scale (VAS) to assess changes in pain during rehabilitation. A 2-cm or greater change in VAS score for usual or worst knee pain in the past week represents meaningful difference.27 SOR: B 10. Clinicians should use patient-reported outcome mea- sures, such as the Anterior Knee Pain Scale (AKPS) or the Lower Extremity Functional Scale (LEFS), to assess function in individuals with PFP. For the AKPS, a 10-point or greater change represents the minimal clinically important difference.27 For the LEFS, an 8- point or greater change represents the minimal detectable change.28 SOR: B Nonsurgical Treatment 11. Due to the complexity of managing PFP, clinicians should develop and implement a multimodal plan of care. The plan of care should include gluteal- and BACKGROUND AND LITERATURE REVIEW Risk Factors Although PFP is a common knee problem among physically active individuals, its causes have remained elusive. Dye et al69 characterized PFP as the ‘‘black hole of orthopaedics’’ because of its poorly identiﬁed causative factors. They believed that PFP resulted from irritation of innervated structures of the patellofemoral joint (eg, inﬂamed synovial and fat pad tissues) as a result of excessive joint loading.70 This theory has led to the identiﬁcation of factors that can lead to increased patellofemoral joint loading, such as (1) altered lower extremity kinematics and kinetics, (2) decreased muscle strength and neuromuscular recruitment, (3) faulty struc- tural alignment, and (4) reduced ﬂexibility. A limitation of many studies has been the use of retrospective data, which cannot distinguish between cause and effect.15 Although retrospective data can identify impairments to address during rehabilitation, these prob- lems did not necessarily exist before the onset of PFP. For example, individuals with PFP responded favorably to gluteal muscle-strengthening exercises30,71; however, glu- teal muscle weakness was not a risk factor.5,20 To better understand the causes of PFP, this literature review includes only ﬁndings from investigations that prospectively fol- lowed otherwise healthy individuals who eventually developed PFP. Lower Extremity Kinematics. Altered lower extremity movement patterns have been theorized to contribute to PFP. The term dynamic Q-angle describes the negative effect of altered lower extremity kinematics on the patellofemoral joint.72 Brieﬂy, the Q-angle represents the resultant lateral pull of the patella and is the angle formed by 1 line drawn from the anterior-superior iliac spine to the midpatella and a second line drawn from the midpatella to the tibial tuberosity. Excessive hip adduction or internal rotation (or both) place the patella in a more medial position relative to the anterior-superior iliac spine, resulting in an increased dynamic Q-angle. Increased tibial external rotation and knee abduction place the tibial tubercle in a more lateral position relative to the patella, which also increases the Q-angle. Together, these motions can increase the laterally directed forces on the patella, leading to lateral patellofemoral joint compression and pain.73–75 To date, limited and conﬂicting data exist regarding an association between altered lower extremity kinematics and an increased risk of developing PFP. Inconsistent ﬁndings may reﬂect differences in the patient populations studied and the tasks used to assess kinematics. From a systematic review of 7 articles with meta-analysis, Pappas and Wong- Tom21 concluded that additional prospective studies were needed to better understand the risk factors associated with PFP. However, they stated that excessive knee abduction during landing tasks may contribute to the onset of PFP. Boling et al5 reported that military recruits who developed PFP demonstrated, on average, 768 6 128 of peak knee ﬂexion and 88 6 98 of peak hip internal rotation during a jump landing. Participants who did not develop PFP exhibited, on average, 818 6 148 and 78 6 88 of peak knee ﬂexion and hip internal rotation, respectively. 822 Volume 53 Number 9 September 2018 generated greater vertical peak forces at the lateral heel and the second and third metatarsals during running.25 Thijs et al84 also found that military recruits who developed PFP walked with the foot in a more supinated position, as evidenced by a pattern of greater lateral foot pressure. The authors concluded that these plantar-pressure patterns could decrease the foot’s ability to dampen ground reaction forces, resulting in increased impact loading to the knee and eventual PFP.25 However, a systematic review with meta- analysis18 provided limited evidence of an association between dynamic foot function (ie, plantar pressures) and the risk of developing PFP. Additional prospective studies are needed to better understand the role of dynamic foot function in the onset of PFP. Lower Extremity Muscle Strength. Clinically, hip and knee weakness has been identiﬁed in individuals with PFP85 and has led to studies of muscle weakness and PFP onset. Decreased gluteal muscle strength may result in increased hip adduction and internal rotation, motions theorized to increase patellofemoral joint stress.72 Quadriceps weakness may contribute to PFP by increasing lateral patellar tracking and patellofemoral joint loading.5,24,86 From a systematic review with meta-analysis of 24 articles, Rathleff et al19 reported moderate-to-strong evidence of no correlation between decreased isometric hip-abductor, external-rotator, and hip-extensor strength and PFP onset. They noted that hip-muscle weakness became evident after PFP developed, suggesting that hip weakness may have arisen from inactivity after symptoms began. A limitation of prior studies that evaluated hip strength as a predictor of PFP has been little attention to other aspects of muscle performance (eg, muscle endurance and rate of force development).19 Souza and Powers87 found that reduced hip-extension endurance, not isometric strength, was the sole hip-muscle predictor of increased hip internal rotation during running in females with PFP. Although these authors used retrospective data, their ﬁndings highlighted the need to examine different strength factors. Individuals with PFP are known to exhibit hip weakness that most likely evolved from inactivity due to pain.19,85,88 More important, those with PFP have reported improve- ments in pain and function from hip-strengthening exercises.30,71 This trend supports the current thought that isometric hip weakness is a result and not a cause of PFP.19 However, future prospective investigators should assess other aspects of hip strength (eg, isokinetic concentric and eccentric strength) and performance (eg, muscle endurance) to identify additional possible hip inﬂuences on PFP. Researchers5,24,89–91 have also evaluated the isometric strength, isokinetic peak torque, and functional perfor- mance of the quadriceps and hamstrings as risk factors for PFP. They identiﬁed decreased quadriceps strength but not decreased hamstrings strength as a predictor of PFP. Using handheld dynamometry, Boling et al5 reported that asymptomatic individuals entering the US Naval Academy who developed PFP generated, on average, less isometric quadriceps force (equal to 46% 6 0.09% of body mass compared with 52% 6 0.12% of body mass in those who did not develop PFP) at baseline. Results from 2 meta- analyses21,22 further supported isometric quadriceps weak- ness as a risk factor. With respect to functional perfor- mance, Witvrouw et al24 found that individuals who went decreased knee ﬂexion and increased hip adduction and internal rotation during running and landing activities) and kinetics (eg, increased knee-abduction moments) are likely causative factors. Therefore, investigators should examine a combination of biomechanical factors to identify a risk proﬁle for developing PFP. Isometric hip weakness has not been shown to be a risk factor, yet retrospective data87 have revealed associations between other aspects of hip-muscle function and PFP. This ﬁnding highlights the need to determine if reduced hip-muscle concentric and eccentric strength, functional performance, and endurance lead to PFP. Identifying potential risk factors among males and females, individuals participating in a sport-speciﬁc activity, and adolescents may provide further insight.80 Finally, PFP is a chronic problem.9,11 Therefore, certain psychological (eg, coping strategies, fear-avoidance beliefs95) and pain-perception (eg, central sensitization) factors may play roles and deserve attention.13 Pain and Functional Outcome Measures Appropriate pain and functional outcome measures are needed to help determine if an individual with PFP receiving treatment is responding in a clinically meaningful manner.13 Common measures used to assess pain and function in patients with PFP include a 10-cm VAS, the AKPS, the LEFS, the Functional Index Questionnaire, and the global rating of change. Crossley et al27 examined the test-retest reliability, validity, and responsiveness of all these measures except the LEFS for this patient population. The 10-cm VAS for usual and worst pain in the past week and the AKPS represented reliable and valid measures of pain and function in individuals with PFP. Also, each measure was responsive, meaning that a change could show either an improvement in or worsening (ie, sensitivity to change28) of pain and function. The minimal clinically important difference, deﬁned as the smallest change in a score that is clinically meaningful for a patient,96 was 2 cm on the VAS for pain and 10 points on the AKPS score for function.27 The LEFS, another popular functional outcome measure, may be an equally reliable and responsive measure for individuals with PFP. Watson et al28 reported excellent reliability and responsiveness for this scale. Unlike Cross- ley et al,27 they calculated the minimal detectable change. Although similar to the minimal clinically important difference, the minimal detectable change represents the smallest change not attributable to measurement error.28 The minimal detectable change for the LEFS was 8 points. In summary, clinicians should consider a 2-cm change in the VAS score for usual and worst pain in the clinically meaningful. A 10-point change in the AKPS score can be useful to identify a clinically meaningful change in function. It is noteworthy that the 8-point minimal detectable change for the LEFS suggests it is a slightly more responsive measure of change than the AKPS. Therefore, clinicians should use the LEFS to identify more subtle functional changes.28 Nonsurgical Treatment Due to its multifactorial causes, PFP is one of the most difﬁcult knee problems to manage.13 To date, an over- whelming amount of evidence exists for the use of 824 Volume 53 Number 9 September 2018 Figure. Summary of ‘‘Best Practice Guide for foot mobility may beneﬁt from foot orthoses as part of a multimodal strategy.101 Therefore, a possible limitation of the Collins et al100 study was the use of foot orthoses without regard for foot mobility. Future authors should examine the beneﬁts of multimodal physical therapy and foot orthoses for individuals with PFP and excessive midfoot mobility. Rathleff et al77 conducted a systematic review to examine the beneﬁts of multimodal interventions based on investi- gations with a minimum of 1-year follow-up data. They concluded that exercises designed to improve hip and knee strength and neuromuscular control were the best interven- tion options. Interestingly, this systematic review included outcomes for adolescents,102 38% of whom responded favorably to a multimodal intervention, a smaller percent- age than among adults (62%103 and 81%100 ). The researchers11 determined that adolescents presented with a longer duration of pain, a factor suggestive of a poor prognosis. More importantly, ﬁndings from this review highlighted the need to understand PFP in adolescents, who may not have the same underlying condition as adults and may beneﬁt from different intervention strategies.77 At this time, much work is needed regarding the etiology and management of PFP in children and adolescents.80 Although peer-reviewed evidence has been valuable for identifying important intervention strategies, knowledge gained from clinical experience may be equally useful. Barton et al29 performed a systematic review of interven- tions for PFP and integrated interview data from clinicians and researchers considered experts in this ﬁeld. This study was unique because its overarching purpose was to integrate ﬁndings from the scientiﬁc literature into clinical decision making. The interviewers queried respondents on their clinical reasoning, impression of the body of literature, approaches full extension, the patella has less contact within the femoral trochlea, leading to increased patello- femoral joint stress.42,43 The opposite effect occurs during weight-bearing knee extension, when the quadriceps generates less force as it extends the knee from 908 to 08 of ﬂexion. Although the patella has less femoral contact area as it approaches full knee extension, less quadriceps force is required.83,111 The relatively greater decrease in quadriceps force compared with patellar contact results in less overall patellofemoral stress.42,43 Understanding these biomechanical principles is critical to promoting pain-free quadriceps exercises. Nonweight-Bearing Quadriceps-Strengthening Exercises. Clinicians have prescribed isometric quadri- ceps contraction setting and straight-leg–raise exercises to address quadriceps weakness, an approach shown to reduce pain and improve quadriceps strength.112–115 However, a signiﬁcant limitation has been their relatively isometric nature and strengthening focused on a single point in the knee’s range of motion. Isokinetic exercise allows controlled movement speed within a speciﬁc arc of motion. Hazneci et al116 and Alaca et al117 prescribed a 6-week isokinetic quadriceps program at speeds of 608/s and 1808/s. Patients displayed an average 2.4-cm improvement in VAS scores116,117 after the training.116,117 Limitations of isokinetic exercise have been equipment cost and availability. Weight-Bearing Quadriceps-Strengthening Exercises. Clinicians also prescribe weight-bearing exercises because they better simulate greater quadriceps eccentric loading during functional activities.44 In addi- tion, weight-bearing exercises enable individuals to target the quadriceps in lesser degrees of knee ﬂexion while minimizing overall patellofemoral joint stress.42,43 Be- cause individuals with PFP demonstrated both hip85 and quadriceps21,22 weakness, weight-bearing exercise allows for the activation of multiple muscle groups simulta- neously. Weight-bearing quadriceps exercises (eg, wall slides, lateral step-downs, and mini-squats) have been shown to beneﬁt individuals with PFP. Patients with PFP have demonstrated improvement (2.9-cm decrease) in VAS scores as soon as 4 weeks into a 6-week program.118 Speciﬁc nonweight-bearing hip-abductor and external- rotator strengthening exercises provided beneﬁts beyond those gained from weight-bearing quadriceps exercise.35 Participants who completed a 6-week weight-bearing quadriceps program plus isolated nonweight-bearing glute- al-strengthening exercises showed greater decreases (3.2 versus 2.3 cm) in VAS and increases (13.7 versus 8.6 points) in AKPS scores than those who performed only weight-bearing quadriceps exercises.35 In summary, these ﬁndings35,118 support the use of both weight-bearing quadriceps exercises and speciﬁc nonweight-bearing glute- al-strengthening exercises. Nonweight-Bearing Versus Weight-Bearing Quadriceps- Strengthening Exercises. Individuals with PFP have also beneﬁted from exercise programs incorporating both non- weight-bearing and weight-bearing quadriceps exercis- es.54,57,119,120 For a 5-year period, Witvrouw et al108 prospectively followed patients who had completed a 5- week protocol of either nonweight-bearing or weight-bearing quadriceps exercises. At the end of the follow-up period, all 826 Volume 53 Number 9 September 2018 Table 1. Sample Exercises Designed to Target the Study Exercise Dolak et al34 Straight-leg raisesa Supine knee extension (308 to 08)a Ferber et al32 Standing terminal knee extensionb Wall slide (458 knee extension) Single-legged squat (08 to 458) Fukuda et al38 Seated knee extension Seated leg press (08 to 458) Herrington and Al-Sherhi124 Seated knee extension (908 to 08)a Seated leg press (08 to 908) Khayambashi et al31 Seated knee extension (308 to 08)b Standing mini-squats (308 to 08)b Song et al121 Unilateral seated a Cuff weight resistance. b Elastic band resistance (all used a progression c Number of repetitions varied depending on the descent maneuver. After completing a 14-week trunk- and hip-focused exercise program, both patients demonstrated improved VAS (preintervention pain ¼ 4/10 and 7/10; postintervention ¼ 0/10 and 2/10, respectively) and AKPS (9- and 14-point improvements) scores and generated greater quadriceps, gluteus maximus, gluteus medius, hip internal-rotator, and hip external-rotator isometric force during strength testing. One participant underwent a biomechanical examination during stair descent and exhibited 48 more hip external rotation and 6.48 less hip adduction after completing the intervention. This result suggested that strength gains transferred to performing stair descent with the hip in a more optimal position, one that reduced the dynamic Q-angle. These ﬁndings provided preliminary support for the importance of trunk and hip strengthening in this patient population. Others have continued to investigate the importance of proximal strengthening. Tyler et al126 examined 35 patients with PFP who performed 6 weeks of nonweight-bearing and weight-bearing hip-strengthening exercises. On aver- age, VAS scores decreased by 2.2 cm. However, the effect of the weight-bearing exercises on quadriceps strength was unclear. Fukuda et al38 randomized sedentary females with PFP into 1 of the following groups: quadriceps exercises, isolated hip and quadriceps exercises, and control (no intervention). After 4 weeks, patients in both exercise groups had greater improvements in numeric pain-rating scale (NPRS), LEFS, and AKPS scores than the control group. However, only those who performed the additional hip exercises demonstrated clinically meaningful improve- ments in VAS scores during stair ascent (2.2-cm decrease) and descent (2.6-cm decrease). These ﬁndings were consistent with those of other investigators33,35 who reported greater improvements in VAS scores with the addition of hip-abductor and hip external-rotator exercises to a traditional quadriceps-strengthening program. Partici- pants in the quadriceps and isolated hip and quadriceps exercise groups showed improvements in LEFS (10- and 16.6-point increases, respectively) and AKPS (10.2- and 15-point increases, respectively) scores. Fukuda et al40 also followed their exercise groups at 3, 6, and 12 months postintervention. Those who performed both hip and quadriceps exercises reported continued improve- Table 2. Sample Exercises Designed to Target the Study Exercise Dolak et al34 Side-lying hip abductiona Seated hip external rotationb Isometric combined in quadruped positionb Earl and Hoch36 Abdominal drawing Side-lying combined rotationb Prone planks Side planks Fukuda et al38 Standing hip abductionb Side-lying hip abductiona Seated hip external rotationb Side stepping Khayambashi et al39 Standing hip abductionb Seated hip external rotationb Nakagawa et al33 Transversus abdominis position Side-lying combined rotationb Isometric combined in the quadruped position Pelvic drop exercise a Cuff weight resistance. b Elastic band resistance (all used a progression c Number of repetitions varied depending on the both VAS score (3.5-cm decrease) and isometric hip strength. Findings from both investigations34,36 provided preliminary evidence for the beneﬁts of early trunk and hip strengthening. A sample of the exercises used in these investigations is shown in Table 2. Hip and Trunk Exercises Versus Quadriceps Exercises. More recent investigators31,32,41 have speciﬁcally compared the isolated effects of hip and trunk exercises versus quadriceps exercises for individuals with PFP. Ferber et al32 assessed VAS and AKPS scores in 199 patients with PFP who participated in either a 6-week hip- and core- or quadriceps-exercise intervention. All patients, regardless of group assignment, demonstrated clinically meaningful improvements in VAS (3-cm decrease) and AKPS (11- point increase) scores. Those assigned to the hip and core group displayed a decrease in VAS score at the end of week 3, a week sooner than those in the quadriceps group. et al34 also found that individuals who initially exercises improved sooner than those who initially performed quadriceps exercises. Khayambashi et al31 assessed changes in pain and function in patients who completed a program of either 2 hip or 2 quadriceps exercises using a progression of resistance bands. Those in the hip group performed side- lying hip-abduction and seated hip–external-rotation exer- cises. Patients in the quadriceps group performed a nonweight-bearing (seated knee extension from 308 to 08 of knee ﬂexion against a resistance band) and a weight- bearing (squat from 308 to 08 of knee ﬂexion against a resistance band) knee-extension exercise. The strengthen- ing exercises were performed during a 20-minute session, 3 times a week for 8 weeks. Although all patients beneﬁted, those in the hip-exercise group exhibited better outcomes with respect to VAS (5.5-cm decrease compared with 3.6- cm decrease for the quadriceps group) and WOMAC scores. At the 6-month follow-up assessment, participants 828 Volume 53 Number 9 September 2018 results further support the importance of hip-strengthening exercise in managing patients with PFP. Movement Retraining. Researchers49,50,129 have also focused on the importance of movement-pattern modiﬁcation. Noehren et al49 assessed hip mechanics in 10 female runners with PFP before, immediately after, and 1 month after completing a real-time 2-dimensional kinematic-feedback intervention. Patients ran on a treadmill 4 times a week for 2 weeks. Initially, they ran for 15 minutes and were given real-time visual kinematic feedback to minimize hip adduction. As the duration of the running session increased, the amount of real-time visual kinematic feedback decreased. After 2 weeks, patients exhibited 5.18 less hip peak adduction, 2.58 less peak hip internal rotation, and 2.38 less peak contralateral pelvic drop during the stance phase of running. Importantly, they showed improvements in VAS (4.3-cm decrease) and LEFS (11-point increase) scores. All beneﬁts were maintained at the 1-month follow up. However, a limitation of the Noehren et al study49 was the use of expensive motion-analysis equipment not conducive to most clinical settings. To address this concern, Willy et al50 sought to identify changes in hip mechanics during running using mirror and verbal feedback. These authors also assessed hip mechanics during a single-legged squat and a step-down task before and after training. After completing the 2-week training program, patients displayed similar improvements in VAS scores (3.2-cm decrease), LEFS scores (9-point increase), and peak hip adduction (5.98 decrease) during running as those in the Noehren et al49 study. They also exhibited 48 and 3.58 less peak hip adduction during a single-legged squat and step-down task, respectively. These ﬁndings suggested they were able to transfer the newly acquired skill (ie, less hip adduction during running, suggestive of a smaller dynamic Q-angle) to other functional tasks. Most important, patients main- tained the improved VAS and LEFS scores at the 3-month follow-up assessment. Prophylactic Equipment and Physical Agents Patellar Taping. The original premise of patellar taping was that tape could correct patellar positioning and tracking and facilitate VMO activation during dynamic movement. However, evidence130–132 has now suggested that patellar taping does not maintain optimal patellar position after exercise or necessarily facilitate quadriceps neuromuscular activity, although it may promote pain-free quadriceps exercise.46 Callaghan and Selfe133 conducted a systematic review of 5 articles but did not make a conclusive recommendation regarding the use of patellar taping, either with or without exercise. They noted the limited available evidence and the need for higher-quality studies, especially to measure clinically important short-term and long-term outcomes. Despite conﬂicting evidence, patellar taping should be considered a treatment strategy. Clinicians with expertise in the management of individuals with PFP recommend taping, at least for an immediate short-term period, if needed for pain relief.29 Patellar Bracing. Bracing is an alternative to patellar taping. Advantages of bracing include fewer adverse skin reactions and minimal patient education regarding orthosis use with the following variables: (1) age greater than 25 years, (2) height less than 165 cm, (3) worst pain on a VAS less than 53.25 mm, and (4) midfoot width difference.11 mm between nonweight bearing and weight bearing. With 3 variables present, the positive likelihood ratio was 8.8, and the success rate improved from 40% to 86% with orthosis use. In summary, individuals with PFP who have increased overall foot mobility (eg, 58 peak rear- foot eversion during gait138 or increased midfoot mobili- ty101,139) may beneﬁt from foot orthoses as part of a multimodal intervention.29,45 Neuromuscular Electrical Stimulation. Inhibition of the VMO may contribute to PFP,54 which has prompted the use of neuromuscular electrical stimulation (NMES) to facilitate VMO activity. Callaghan et al52,53 speciﬁcally examined the isolated effect of NMES on individuals with PFP. Their patients received NMES over a 6-week period and demonstrated improvements in quadriceps isometric and isokinetic strength, quadriceps endurance, and step-test performance (number of times the person could step up and down from a 25-cm step without pain). However, the VAS (1.5-cm or less decrease) and AKPS (7.8-point or less increase) score changes were not clinically meaningful and do not support the isolated use of NMES. Bily et al54 investigated the potential additional beneﬁts gained from the use of NMES with exercise. Patients in the ﬁrst group performed nonweight-bearing and weight- bearing quadriceps exercises. Those in the second group performed identical exercises as the ﬁrst but also received two 20-minute sessions of NMES every day. All patients demonstrated similar improvements in VAS scores at the 12-week (4.0- and 4.1-cm decreases for the exercise-only and exercise-plus-NMES groups, respectively) and 52- week (4.9- and 3.8-cm decreases for the exercise-only and exercise-plus-NMES groups, respectively) follow-ups com- pared with baseline. Although participants who received exercise plus NMES had a greater improvement (16-point increase) in AKPS score than those in the exercise-only group (7-point increase) from baseline at 12 weeks, all had similar total AKPS scores (95/100 and 94/100 points for the exercise-only and exercise-plus-NMES groups, respective- ly) at the 52-week follow-up. Based on these data,52–54 we conclude that NMES use provided minimal, if any, additional beneﬁt over exercise alone. Its use is not recommended for the management of PFP. Ultrasound, Cryotherapy, Phonophoresis, and Iontophoresis. Lake and Wofford 58 conducted a systematic review to address the effects of physical agents on PFP. They determined that the use of physical agents was no more effective than exercise. Low-Level Laser Therapy. Low-level laser therapy, approved for clinical use in the United States since 2002, is an emerging physical agent theorized to modulate tissue healing. Although it is promising for wound and fracture healing, the current evidence does not support its use in those with PFP.51,58 Future investigations are needed to determine its clinical utility. Surgical Interventions Nonsurgical management is the preferred treatment approach for PFP.45,109 However, cases arise in which an individual with long-term PFP may consider surgical 830 Volume 53 Number 9 September 2018 Therefore, an osteotomy may be considered to reduce overall patellofemoral stress (force per unit surface area83) via structural realignment. A wide variety of osteotomies have been promoted, and a thorough discussion is beyond the scope of this position statement. However, their overarching goal is to reposition the patella with respect to the femur or to reposition the patella in the trochlear groove. The speciﬁc objective is to balance or redirect forces acting at the patellofemoral articulation during active knee extension. Laboratory testing has shown that surgery, at best, may reduce the overall magnitude of forces applied via the quadriceps to the patella. Using a cadaveric model, Ferguson et al142 measured patellar stress after elevating the patellar tendon via tibial tubercle displacement. They reported that 0.5 in (1.3 cm) of tendon elevation resulted in decreased contact stress. Elevation beyond this amount afforded little additional beneﬁt. Surgical realignment has been useful for redistributing rather than reducing patellofemoral joint forces. Force redistribution may be achieved by realigning the forces acting on the joint, increasing the contact area, relationship has led to procedures that involve anteromedi- alization (AMZ) of the tibial tuberosity, also known as the Becker or Fulkerson osteotomy. Beck et al143 used a cadaveric model to measure changes in patellar contact pressure after AMZ. They found that AMZ of the tibial tubercle effectively shifted patellofemoral joint loading to a more proximal and medial aspect of the trochlea. They concluded that this change would reduce overall lateral patellofemoral joint stress and may beneﬁt individuals with PFP. Long-term investigations after AMZ have supported its use in a cohort of individuals with PFP. Dantas et al62 reported improvements in average Lysholm scores from 63.3 to 98 at 52 months after AMZ. They also noted that patients with patellar instability but no signiﬁcant articular cartilage changes were more likely to beneﬁt from AMZ. Karamehmetoglu et al63 reported similar favorable out- comes. They followed 18 patients (21 knees) an 28 months after AMZ and observed that 85.7% of patients reported good to excellent results. CONCLUSIONS Although PFP is one of the most common lower extremity diagnoses experienced by active individuals, it continues to be among the most challenging to manage. A multifactorial problem, PFP has numerous causes resulting from irritation of innervated patellofemoral joint struc- tures.70,144 However, a common theme is that excessive patellofemoral joint loading not only leads to PFP but must be minimized during rehabilitation. From a biomechanical standpoint, repetitive out-of-plane motions from the hip (adduction and internal rotation) and knee (abduction) lead to increased patellofemoral joint loading.17,78 From a neuromuscular standpoint, quadriceps weakness and tightness are other sources of abnormal joint loading.5,24 Identifying these risk factors can framework for advancing the development and implemen- tation of prevention programs. To date, the only recommendation for a PFP prevention program is to include lower extremity stretching and weight- population-based study among 504 adolescents. BMC Musculoske- let Disord. 2013;14:225. (Level of evidence [LOE]: 2) 2. Wood L, Muller S, Peat G. The epidemiology of patellofemoral disorders in adulthood: a review of routine general practice morbidity recording. Prim Health Care Res 164. (LOE: 3) 3. Nimon G, Murray D, Sandow M, Goodfellow J. Natural history of anterior knee pain: a 14- to 20-year follow-up of nonoperative management. J Pediatr Orthop. 1998;18(1):118–122. (LOE: 2) 4. Molgaard C, Rathleff MS, Simonsen O. Patellofemoral pain syndrome and its association with hip, ankle, 16- to 18-year-old high school students: a single-blind case- control study. J Am Podiatr Med Assoc. 2011;101(3):215–222. (LOE: 2) 5. Boling MC, Padua DA, Marshall SW, Guskiewicz K, Pyne S, Beutler A. A prospective investigation of for patellofemoral pain syndrome: the Joint and Prevent ACL Injury (JUMP-ACL) cohort. Am J Sports Med. 2009;37(11):2108–2116. (LOE: 2) 6. Taunton JE, Ryan MB, Clement DB, McKenzie DC, Lloyd-Smith DR, Zumbo BD. A retrospective case-control analysis of 2002 running injuries. Br J Sports Med. 2002;36(2):95–101. 7. Barber Foss KD, Myer GD, Chen SS, Hewett TE. Expected prevalence from the differential diagnosis adolescent female athletes during preparticipation Train. 2012;47(5):519–524. (LOE: 2) 8. Boling MC, Padua D, Marshall S, Guskiewicz Gender differences in the incidence and prevalence oral pain syndrome. Scand J Med Sci Sports. (LOE: 2) 9. Collins NJ, Bierma-Zeinstra SM, Crossley Vicenzino B, van Middelkoop M. Prognostic factors for patello- femoral pain: a multicentre observational 2013;47(4):227–233. (LOE: 1) 10. Stathopulu E, Baildam E. Anterior knee pain: up. Rheumatology (Oxford). 2003;42(2):380–382. (LOE: 2) 11. Lankhorst NE, van Middelkoop M, Crossley predict a poor outcome 5–8 years after the diagnosis of patellofemoral pain: a multicentre observational Sports Med. 2016;50(14):881–886. (LOE: 2) 12. Blond L, Hansen L. Patellofemoral pain syndrome year retrospective follow-up study of 250 Belg. 1998;64(4):393–400. (LOE: 2) 13. Witvrouw E, Callaghan MJ, Stefanik JJ, et consensus statement from the 3rd International Research Retreat held in Vancouver, September Med. 2014;48(6):411–414. (LOE: 3) 14. Ebell MH, Siwek J, Weiss BD, et al. Strength of recommendation taxonomy (SORT): a patient-centered approach in the medical literature. Am Fam Physician. (LOE: 3) 15. Noehren B, Hamill J, Davis I. Prospective evidence for a hip etiology in patellofemoral pain. Med Sci Sports Exerc. 2013;45(6):1120–1124. (LOE: 2) 16. Stefanyshyn DJ, Stergiou P, Lun VM, Meeuwisse WH, Worobets JT. Knee angular impulse as a predictor of runners. Am J Sports Med. 2006;34(11):1844–1851. (LOE: 2) 17. Myer GD, Ford KR, Di Stasi SL, Foss KD, Micheli LJ, Hewett TE. High knee abduction moments are common risk factors for patellofemoral pain (PFP) and anterior cruciate ligament (ACL) injury in girls: is PFP itself a predictor Br J Sports Med. 2015;49(2):118–122. (LOE: 2) 18. Dowling GJ, Murley GS, Munteanu SE, et al. Dynamic foot function as a risk factor for lower limb review. J Foot Ankle Res. 2014;7(1):53. (LOE: 2) 832 Volume 53 Number 9 September 2018 36. Earl JE, Hoch AZ. A proximal strengthening program improves pain, function, and biomechanics in women with patellofemoral pain syndrome. Am J Sports Med. 2011;39(1):154–163. (LOE: 2) 37. Ferber R, Kendall KD, Farr L. Changes in knee biomechanics after a hip-abductor strengthening protocol for runners oral pain syndrome. J Athl Train. 2011;46(2):142–149. (LOE: 2) 38. Fukuda TY, Rossetto FM, Magalhães E, Bryk FF, Lucareli PR, de Almeida Aparecida Carvalho N. Short-term effects and lateral rotators strengthening in females pain syndrome: a randomized controlled clinical trial. J Orthop Sports Phys Ther. 2010;40(11):736–742. (LOE: 2) 39. Khayambashi K, Mohammadkhani Z, Ghaznavi K, Lyle MA, Powers CM. The effects of isolated hip abductor and external rotator muscle strengthening on pain, health in females with patellofemoral pain: a randomized Orthop Sports Phys Ther. 2012;42(1):22–29. (LOE: 2) 40. Fukuda TY, Melo WP, Zaffalon BM, et al. Hip posterolateral musculature strengthening in sedentary women with patellofemoral pain syndrome: a randomized controlled clinical follow-up. J Orthop Sports Phys Ther. 2012;42(10):823–830. 2) 41. Baldon Rde M, Serrao FV, Scattone Silva R, Piva SR. Effects of functional stabilization training on pain, function, and lower extremity biomechanics in women with patellofemoral pain: a randomized clinical trial. J Orthop Sports Phys Ther. 2014;44(4):240–A8. (LOE: 2) 42. Steinkamp LA, Dillingham MF, Markel MD, Hill JA, Kaufmen KR. Biomechanical considerations in patellofemoral Am J Sports Med. 1993;21(3):438–444. (LOE: 3) 43. Powers CM, Ho KY, Chen YJ, Souza RB, Farrokhi S. Patellofem- oral joint stress during weight-bearing and non-weight-bearing quadriceps exercises. J Orthop Sports Phys 327. (LOE: 3) 44. Bolgla LA, Malone TR. Exercise prescription and patellofemoral pain: evidence for rehabilitation. J Sport 88. (LOE: 2) 45. Collins NJ, Bisset LM, Crossley KM, Vicenzino B. Efﬁcacy of nonsurgical interventions for anterior knee and meta-analysis of randomized trials. Sports 49. (LOE: 1) 46. Bolgla LA, Boling MC. An update for the conservative manage- ment of patellofemoral pain syndrome: a systematic review of the literature from 2000 to 2010. Int J Sports 125. (LOE: 2) 47. Napier C, Cochrane CK, Taunton JE, Hunt MA. Gait modiﬁcations 2018;53(9):820–836 Position Statement College, Boston CT; jjTorrey Pines of Southern used various treatment strategies that have not necessarily benefitted all patients. Suboptimal outcomes may reflect the need to integrate clinical practice with scientific evidence to facilitate clinical decision making. Recommendations: The recommendations are based on the best available evidence. They are intended to give athletic trainers and other health care professionals a framework for identifying risk factors for and managing patients with PFP. factors may Key Words: anterior knee pain, patella, risk factors, therapeutic exercise, hip musculature, quadriceps strength and involves an intricate interplay of anatomical variations and biomechanical abnormalities.13 The purpose of this position statement is to present recommendations for health care providers regarding the identiﬁcation of risk factors and management of PFP. The recommendations outlined here represent the best available evidence to date. Continued research is necessary to reﬁne these recommendations and to advance our understanding of this complicated condition. The National Athletic Trainers’ Association (NATA) suggests the following guidelines to identify risk factors for and manage patients with PFP. The strength of recommen- dations is based on the Strength of Recommendation (SOR) Taxonomy criteria.14 In the SOR Taxonomy, the letter indicates the consistency and evidence-based strength of the recommendation (A has the strongest evidence base). quadriceps-strengthening exercises, patient education (ie, contributing factors, importance of exercise, rehabilitation expectations), and activity modiﬁca- tion.29 Individuals with PFP who complete an 8-week gluteal-strengthening program reported greater im- provements in pain and health status 6 months after completing rehabilitation compared with those who completed an 8-week quadriceps-strengthening pro- gram.30–32 SOR: A 12. For individuals with PFP, clinicians should prescribe an initial 3-week program of isolated gluteal-strength- ening exercises before a program of quadriceps- strengthening exercises.31–41 SOR: B 13. Clinicians should prescribe interventions that address trunk-muscle (eg, abdominal oblique, rectus abdomi- nis, transversus abdominis, erector spinae, and multif- idi) control and capacity in individuals with PFP.31,32,36,40,41 SOR: A 14. To minimize patellofemoral joint stress, patients should perform nonweight-bearing quadriceps exercis- es between 458 and 908 of knee ﬂexion and weight- bearing quadriceps exercises between 08 and 458 of knee ﬂexion.42–44 SOR: C and 15. Patellar taping appears to be beneﬁcial if it enables for the patients with PFP to exercise in a pain-free man- ner.29,45,46 SOR: B 16. Movement-retraining programs that incorporate either real-time visual or auditory feedback can beneﬁt individuals with altered lower extremity gait mechan- ics such as excessive hip adduction or hip internal rotation or increased knee valgus (or a combination of these).47,48 SOR: A 17. Movement retraining that emphasizes keeping the pelvis level and the knees facing forward during dynamic activities has been beneﬁcial for females with PFP. Providing visual and verbal feedback to the patient about keeping the pelvis level and knees facing forward appears to be an important component of this training.49,50 SOR: B 18. Foot orthoses as an adjunct intervention in combina- tion with other treatment strategies provide some beneﬁt to patients with PFP.45 SOR: B 19. Forms of electrotherapy including therapeutic ultra- sound and low-level laser therapy have shown limited effectiveness in the management of PFP.51–58 SOR: B a clinically Surgical Treatment 20. Referral for surgical intervention should be considered only if an individual with PFP presents with either evident lateral patellar compression or patellar insta- bility and has failed to improve despite exhaustive rehabilitation attempts.59–63 SOR: A 21. Lateral retinacular release or lengthening can beneﬁt individuals with PFP who present with excessive lateral patellar tilting but no patellar instability or grade III–IV articular cartilage changes.59–61,64,65 SOR: B 22. Patellofemoral joint realignment procedures, such as the Fulkerson osteotomy, can beneﬁt individuals with PFP and patellar instability.62,66–68 SOR: B Journal of Athletic Training 821 Although all participants displayed similar peak hip internal rotation, the combined effect of hip internal rotation and less knee ﬂexion could lead to increased lateral patello- femoral contact pressure.5 Myer et al76 investigated frontal- plane knee motion (eg, knee abduction) in younger female basketball players (mean age ¼ 13.4 years) during a similar task but did not identify it as a risk factor for PFP. This ﬁnding suggested that, among younger females, different risk factors could contribute to PFP onset.77 Noehren et al15 prospectively followed a cohort of pain-free female runners over a 2-year period. Compared with those who remained asymptomatic and demonstrated 88 6 58 of hip adduction during the stance phase of running, the individuals who eventually developed PFP demonstrated 128 6 38 of hip adduction. However, with respect to rear-foot eversion angle, no between-groups differences existed. These results provided additional information that the PFP onset may be more attributable to altered hip kinematics than to foot kinematics. In summary, out-of-plane motions such as hip adduction and internal rotation can increase lateral patellofemoral joint loading78,79 and most likely contribute to the onset of PFP. The relationship between sagittal-plane and out-of- plane motions also deserves further study.76 It is important to note that activities such as basketball and long-distance running may result in different patterns of altered kinematics.76 Future investigators should examine hip and knee kinematics across different activities and age groups.77,80 Lower Extremity Kinetics. Patellofemoral pain is theorized to result from increased patellofemoral joint stress, deﬁned as force per unit area (ie, quadriceps force applied per unit of patellofemoral joint contact area).70,81 As explained in the ‘‘Lower Extremity Kinematics’’ section, an increased dynamic Q-angle leads to abnormal lateral patellofemoral joint stress.72,82 Increased stress may also occur from the repetitive quadriceps force produced during running and jumping activities. For example, ground reaction forces generated during the landing phase of running and jumping cause the knee to move into ﬂexion and abduction.78,83 In response to the ground reaction force, the quadriceps generates force to control these knee motions. If sufﬁcient, the cumulative effect of quadriceps force generation could lead to increased patellofemoral stress and pain.70 This theory has led to research directed at understanding the role of altered lower extremity kinetics (ie, forces) in PFP onset. Stefanyshyn et al16 assessed knee kinetics during the stance phase of running and prospectively followed these individuals over a 6-month period. Runners who developed PFP generated 19% higher knee-abduction impulses during the stance phase of running than those who remained symptom free. Myer et al17 evaluated knee kinetics during a drop-landing task in middle and high school female basketball players before their competitive season. Those who developed PFP during the season exhibited greater knee-abduction moments during the initial contact phase of the task. Results from both investigations suggested that greater frontal-plane knee loading may contribute to PFP onset. Thijs et al25,84 examined plantar pressures during running in pain-free novice recreational runners and walking in military recruits. Novice runners who developed PFP on to develop PFP demonstrated smaller vertical jumps at baseline compared with those who did not (52 6 3.6 cm versus 56 6 6.3 cm, respectively). Additional prospective studies are needed to provide more data to support the functional performance of the quadriceps and hamstrings as risk factors for the development of PFP. Neuromuscular Factors. Another possible contributor to PFP is a delay in activation of the VMO relative to the VL (VMO onset VL onset). The VMO and VL provide dynamic stabilization to the patella as it tracks in the femoral trochlea.86 Therefore, an imbalance in the onset or activity level (or both) of the VMO relative to the VL could lead to patellar malalignment.92 Witvrouw et al24 observed that individuals who exhibited a delay of 0.31 6 1.4 milliseconds in VMO activation after patellar tendon tap developed PFP. In a follow-up study, Van Tiggelen et al23 assessed VMO onset VL onset during the volitional task of rocking back on the heels. Participants who had a 0.67- millisecond or greater delay in VMO onset developed PFP.23 These ﬁndings highlighted the importance of altered neuromuscular control as another risk factor. Structural Alignment. Lower limb structural alignment may also adversely inﬂuence lower limb motion in a way that increases patellofemoral joint loading.73,78 The lower limb alignment variables that have been investigated as risk factors for PFP include static Q-angle,5,24 foot posture index,84 lower leg-heel frontal-plane alignment,24 and heel- to-forefoot frontal-plane alignment. 24 To date, no research21,22 has supported any of these static measures as risk factors for PFP. Neal et al26 conducted a systemic review with meta-analysis of 21 articles and reported limited evidence for increased navicular drop as a risk factor. They concluded that other factors, such as altered hip kinematics (which have been associated with the development of PFP5,15) in combination with increased navicular drop should be considered. Therefore, the authors of future prospective studies should determine if altered structural alignment combined with other risk factors inﬂuences the risk of developing PFP. Lower Extremity Muscle Flexibility. Lower extremity muscle tightness (eg, quadriceps, iliotibial band, hamstrings, and gastrocnemius) has been identiﬁed in individuals with PFP93,94 and theorized to cause increased patellar compression for the following reasons. First, quadriceps and iliotibial band tightness can compress the patella and promote lateral tracking.94 Second, tightness of the knee ﬂexors, such as the hamstrings and gastrocnemius, can lead to greater quadriceps force being needed to extend the knee. This increase in quadriceps force would be another source of patellar compression. To date, only Witvrouw et al24 have described decreased quadriceps ﬂexibility as a risk factor for the development of PFP. Additional prospective studies are needed to better understand the inﬂuence of tightness of other lower extremity muscles on the onset of PFP. Suggestions for Future Investigations. Although researchers have sought to identify PFP risk factors, many more prospective investigations are needed. Patellofemoral pain is a multifactorial problem with no single contributory factor. 24,92 At this time, the common link among prospective study ﬁndings is that excessive patellofemoral joint loading contributes to PFP onset. Based on our literature review, combined altered kinematics (eg, Journal of Athletic Training 823 nonsurgical treatment and the need to develop and implement treatment strategies based on an individual’s body function and structural impairments, activity limita- tions, and participation restrictions.29,97,98 It cannot be overemphasized that a one-size-ﬁts-all treatment approach is not recommended for this patient population.29,45 A multimodal intervention allows for the integration of various treatment strategies based on examination ﬁndings. Common components of a multimodal intervention are patient education, active interventions, and passive inter- ventions (Figure).29 In the next section, we will summarize the available evidence supporting a multimodal interven- tion. A given component of a multimodal intervention (eg, knee and hip strengthening) offers the opportunity to present more evidence for a speciﬁc treatment strategy within the component (eg, weight-bearing versus non- weight-bearing quadriceps exercises). Therefore, subse- quent subheadings within this section will provide evidence for the use of strategies within a speciﬁc component. This information serves as an evidence-based guide that the clinician may use when developing and implementing an individually tailored, evidence-based PFP rehabilitation program. Multimodal Intervention Crossley et al99 were among the ﬁrst researchers to conduct a multicenter, randomized, double-blinded, place- bo-controlled trial examining the beneﬁts of a multimodal intervention for the treatment of PFP. Participants in the treatment group pursued a program of knee and hip exercises, patellar mobilization, corrective taping, and lower extremity stretching. Participants in the placebo group donned loosely applied tape (ie, tape with no therapeutic application), received sham ultrasound, and applied a nontherapeutic gel to the knee. At the end of the 6-week intervention period, the treatment group reported greater and clinically meaningful improvements in VAS for usual (3.5-cm decrease) and worst (4-cm decrease) pain and AKPS (18-point change) scores than controls. This study’s use of a true control group (ie, participants who received a placebo treatment) supplied a high level of evidence for multimodal interventions. Collins et al100 compared the effects of multimodal physical therapy with or without either prefabricated foot orthoses or ﬂat inserts. At the end of 6 weeks, 93% of those who participated in multimodal physical therapy and 90% of those who participated in multimodal physical therapy plus foot orthoses reported treatment success (deﬁned as moderately or markedly improved on a 5-point Likert scale prior week of global effect). At 12 months, participants who received multimodal physical therapy with or without foot orthoses had at least a 2.0-cm improvement in worst pain on the VAS, a 10-point improvement on the AKPS, and a 2-point improvement on the Functional Index Questionnaire. All these changes represented clinically meaningful improve- ments. These results suggested that the addition of foot orthoses provided no further beneﬁt beyond that of multimodal physical therapy. However, participants who wore foot orthoses reported improvements at the 1-year follow-up. As discussed later in the ‘‘Prophylactic Equipment and Physical Agents’’ section, individuals with increased mid- the Conservative Management of Patellofemoral Pain.’’29 and the need for future research. Best practices for the treatment of PFP were patient education, active interven- tions, and passive interventions (Figure). Their ‘‘Best Practice Guide to Conservative Management of Patello- femoral Pain’’ highlighted that many treatment strategies may beneﬁt this patient population. Most important, clinicians should do their best to develop and implement individually tailored interventions based on each patient’s presentation. The following sections provide information on various intervention strategies that a clinician may (or may not, depending on the patient’s presentation) consider using when developing and implementing a multimodal intervention for individuals with PFP. Therapeutic Exercise Quadriceps Strengthening. Quadriceps strengthening has long been considered the mainstay of treatment for individuals with PFP.104 Clinicians have prescribed these exercises based on the theory that quadriceps weakness105 or delayed VM activation (or both) relative to the VL106,107 can lead to abnormal patellar tracking and lateral patellofemoral joint compression. Furthermore, patients with PFP have responded favorably to quadriceps exercises.104,108–110 Individuals with PFP must perform quadriceps-strength- ening exercises in a pain-free manner, one that reduces the amount of patellofemoral joint stress (quadriceps force per patellar contact area on the femur) and resultant pain.29,44 Powers et al43 found differences in patellofemoral joint stress during nonweight-bearing and weight-bearing quad- riceps exercises. During nonweight-bearing knee-extension exercises, the quadriceps must generate greater force as the knee moves from 908 to 08 of ﬂexion.83 As the knee Journal of Athletic Training 825 participants, regardless of exercise group, maintained AKPS scores (greater than a 10-point increase from baseline), single-legged triple-jump performance, and isokinetic knee strength similar to those values at the 3-month posttreatment time. This ﬁnding suggested that both nonweight-bearing and weight-bearing quadriceps exercises were useful. However, only 20% of all participants were pain free at the 5-year follow up. The fact that 80% had ongoing symptoms agreed with other results3,9 and indicated that a single treatment approach may be insufﬁcient for complete symptom resolution. In summary, nonweight-bearing and weight-bearing quadriceps-strengthening exercises can beneﬁt individuals with PFP. Clinicians should prescribe nonweight-bearing exercises if the rehabilitation goal is to target the quadriceps; weight-bearing exercises should be used to strengthen the quadriceps in a functional manner. The most important point is that quadriceps exercises be performed in a pain-free manner44,46 and in combination with other treatment strategies (ie, multimodal approach).29 Speciﬁc Vastus Medialis Training. Investigators106,121,122 have also examined the effects of speciﬁc VMO training on PFP. Syme et al122 conducted a randomized controlled trial to compare the effects of selective VMO activation, general quadriceps strengthening, and no treatment. All patients who received treatment exhibited similar de- creases (greater than 2 cm) in VAS scores, increases in knee ﬂexion during a step-down test, improved McGill Pain Questionnaire scores, and improved Short Form-36 Health Evaluation questionnaire scores. These ﬁndings suggested that selective VMO-activation exercise pro- vided no additional beneﬁt over general nonweight- bearing and weight-bearing quadriceps exercises. His- torically, data have not supported the ability to selec- tively activate the VMO during exercise.123 Therefore, any quadriceps exercise capable of reversing muscle inhibition most likely accounted for muscle timing improvements. Generalized quadriceps-based exercises are shown in Table 1. Quadriceps Strengthening With Biofeedback. Biofeedback represents another means of facilitating VMO activation. Researchers55–57 have compared changes in PFP using visual feedback (eg, electromyography biofeedback) during quadriceps exercises. Although a popular treatment strategy, biofeedback for enhanced quadriceps activation during exercise provided no more pain relief than quadriceps exercises alone.45,58 Hip and Trunk Strengthening. Powers72,78 theorized that faulty hip kinematics, such as increased adduction and internal rotation, may increase laterally directed forces at the patellofemoral joint (as discussed in the ‘‘Lower Extremity Kinematics’’ subheading in the ‘‘Risk Factors’’ section). From a clinical standpoint, prescribing a combination of hip- and traditional quadriceps- strengthening exercises reduces pain and improves function in individuals with PFP.99,118,119 To better understand the role of the hip and trunk musculature, authors have examined the isolated effects of hip and trunk strengthening. Mascal et al125 were the ﬁrst to report on the beneﬁts of targeted trunk and hip strength- ening. In this case series, they outlined the intervention used for 2 females with PFP who initially demonstrated hip weakness and faulty hip and knee kinematics during a stair- Quadriceps Muscles in Individuals With Patellofemoral Pain Resistance or Repetitions 3 3 10 repetitions (progress resistance from 3% to 7% of body mass) 3 3 10 repetitions 3 repetitions (progress hold time from 30 to 60 s and excursion to 908) 3 3 10 repetitions (progress to 15 repetitions and excursion to 908) (908 to 458)a 3 3 10 repetitions (70% of 1-repetition maximum) 3 3 10 repetitions (70% of 1-repetition maximum) Determined using the daily adjustable progressive resistance exercise program 3 3 20–25-repetition progressionc 3 3 20–25-repetition progressionc leg press (08 to 458) 5 3 10 repetitions (60% of 1-repetition maximum) of elastic band resistance). sets performed for a given level of resistance within a single bout of exercise. ments in NPRS, LEFS, and AKPS scores. Those who performed only quadriceps exercises showed improvement in NPRS scores but not in LEFS and AKPS scores at 6 months. No further changes in these scores occurred between 6 and 12 months. Based on these results, clinicians should develop and implement programs that incorporate both hip- and knee-strengthening exercises. Khayambashi et al39 examined the effect of an 8-week hip-abductor and external-rotator strengthening program on females with PFP. At the end of the program, patients displayed improvements in the VAS (6.5-cm decrease) and Western Ontario and McMaster Universities (WOMAC) questionnaire scores and greater isometric hip-abductor and external-rotator strength. Ferber et al37 reported improved VAS scores (2.5-cm decrease) and greater hip-abductor isometric strength within 3 weeks among recreational runners with PFP who performed isolated hip-abductor exercises. Together, these ﬁndings suggested the potential beneﬁts of isolated hip strengthening for individuals with PFP. Although evidence45,46,127 supports the importance of hip strengthening, quadriceps-strengthening exercises continue to offer a viable treatment approach. To better understand the relationship between hip and quadriceps exercises, Dolak et al34 initially instructed females with PFP to perform a 4-week program of either an isolated hip (eg, nonweight-bearing hip-abduction and external-rotation resistance exercises) or quadriceps (eg, nonweight-bearing short-arc quadriceps and straight-leg–raise resistance exer- cises) program. After the initial 4-week protocol, all patients completed an identical 4-week weight-bearing lower extremity strengthening (eg, single-legged balance, lateral step-downs, and lunges) program. Although all participants reported less pain after 8 weeks (2.2- and 1.6- cm decreases for the initial hip- and quadriceps-exercise groups, respectively), only those in the initial hip-exercise group had a clinically meaningful improvement. Regardless of group assignment, LEFS scores increased by 11 points. These data further support the importance of hip-strength- ening exercises for patients with PFP. Earl and Hoch36 instructed patients to perform speciﬁc trunk-endurance and isolated hip-strengthening exercises, followed by weight-bearing lower extremity strengthening exercises. As in Dolak et al,34 improvements were noted in Journal of Athletic Training 827 Hip and Trunk Muscles in Individuals With Patellofemoral Pain Resistance or Repetitions 3 3 10 repetitions (3% to 7% body weight progression) 3 3 10 repetitions (3% to 7% body weight progression) hip abduction-external rotation 3 3 10 repetitions (3% body weight) 2 3 15 repetitions (10-s hold) hip abduction-external 3 3 10 repetitions (progressed up to 3 3 20 with cuff weight ranging from 2.5–5 lb [1.1–2.3 kg]) 2 3 15 repetitions (10-s hold) 2 3 15 repetitions (10-s hold) 3 3 10 repetitions (10-repetition maximum) 3 3 10 repetitions (70% of 1-repetition maximum) 3 3 10 repetitions (10-repetition maximum) 3 3 1 min 3 3 20–25-repetition progressionc 3 3 20–25-repetition progressionc contraction in quadruped 2 3 15 repetitions (10-s hold) hip abduction-external 2 3 15 repetitions (10-s hold) hip abduction-external rotation 2 3 15 repetitions (10-s hold) on a 20-cm (7.9-in) step 2 3 15 repetitions (10-s hold) of elastic band resistance). sets performed for a given level of resistance within a single bout of exercise. in the hip group maintained their improved VAS scores (0.1-cm decrease from intervention completion to 6-month follow up), while those in the quadriceps group had slightly higher VAS scores (0.7-cm increase from intervention completion to 6-month follow up). These ﬁndings were clinically important because they demonstrated that the beneﬁcial effect of prescribing only 2 hip exercises were maintained for at least 6 months. A limitation of prior investigations31,32,34 has been the inability to determine the effect of strengthening on lower extremity kinematics. Baldon et al41 compared VAS scores and trunk and lower extremity kinematics during a single- legged squat in females with PFP who performed either an 8-week functional-stabilization (eg, trunk-endurance exer- cise, isolated hip-strengthening exercise, lunges, and single- limb stance on an unstable platform) or a traditional Dolak quadriceps-strengthening (eg, leg press, front step-up, wall performed hip squat, straight-leg raise, and nonweight-bearing knee- extension) program. Additionally, patients in the function- al-stabilization program received education on optimal trunk and hip positions during functional tasks such as a squat. Similar to prior research,31,32,34 all patients beneﬁtted regardless of the intervention, but those who completed the functional-stabilization training had greater improvements in VAS scores (5.2-cm decrease compared with a 3.0-cm decrease for the quadriceps group). Those in the functional- stabilization training group also demonstrated less ipsilat- eral trunk lean (3.08 decrease) and hip adduction (11.28 decrease) during a single-legged squat after completing the intervention. In a subsequent analysis, Baldon et al128 examined whether the improvement in trunk and hip kinematics resulted from increased hip strength or better motor control. Increased eccentric gluteal-muscle strength accounted for most of the improved frontal-plane kinemat- ics of the trunk and hip during a single-legged squat. These application, yet currently, limited data support its use. Lun et al134 examined the use of a brace speciﬁcally designed to minimize lateral patellar movement. Patients were randomized into 1 of the following groups: (1) exercise only, (2) patellar brace only, (3) exercise and brace, and (4) exercise and knee sleeve. At the end of the intervention, all participants, regardless of group assignment, demonstrated minimal improvements (1.6- to 1.9-cm decreases) in VAS scores for pain during sport activity. Regarding pain 1 hour after sport activity, all patients experienced meaningful improvements (2.1- to 2.8-cm decrease) in VAS scores. Interestingly, those who only wore a brace had the greatest improvement (2.8-cm decrease). Although bracing alone was more beneﬁcial in reducing some aspects of pain (eg, pain 1 hour after activity), the difference in VAS score compared with exercise alone was only 0.7 cm. Thus, bracing may play an important role in patients who cannot exercise regularly.134 However, clinicians should consider the cost of bracing because exercise alone can provide similar beneﬁts. Knee Bracing. Denton et al135 compared the effect of the additional use of the Protonics knee brace (Protonics Biomechanical Balance Systems, Lincoln, NE) with weight-bearing quadriceps exercise alone. The brace was designed to decrease the quadriceps force needed to extend the knee, thereby reducing patellofemoral stress and facilitating pain-free weight-bearing quadriceps exercise. Patients demonstrated clinically meaningful improvements in AKPS scores (21- and 24-point improvements for exercise alone and exercise with the brace, respectively). Therefore, use of the Protonics brace afforded no signiﬁcant beneﬁt versus weight-bearing quadriceps exercise alone. Considering the cost of this brace, data do not support its use. Foot Orthoses. Results from systematic reviews45,136,137 agreed that the addition of orthoses had no greater beneﬁt than multimodal physical therapy in improving VAS and AKPS scores at the 6-, 12-, and 52-week follow-up periods. However, orthoses should be considered an adjunctive strategy for patients who demonstrate excessive foot pronation during gait.29 Regarding the isolated use of orthoses, Barton et al138 examined the relationships among subjective pain, gait, and orthosis use. Patients initially completed a Likert pain scale and underwent a kinematic evaluation of foot and ankle motion during gait. After wearing orthoses for 12 weeks, those who demonstrated an average of 58 peak rear-foot eversion during gait at baseline reported markedly better pain. Mills et al139 compared changes in self-perceived functional improvement using a global improvement scale (6-point Likert scale) in individuals with PFP who wore orthoses for 6 weeks versus a control group (ie, no treatment). Before the orthoses were prescribed, the researchers measured patients’ midfoot widths in non- weight-bearing and weight-bearing positions. At 6 weeks, those who wore the orthoses displayed better global improvement scale scores than controls. Among the patients who wore the orthoses, those who exhibited an 11-mm greater difference between nonweight-bearing and weight-bearing midfoot mobility were more likely to report a successful outcome. These data138,139 suggested that a certain cohort of individuals with PFP may beneﬁt from orthosis use. Vicenzino et al101 developed a clinical prediction rule for Journal of Athletic Training 829 intervention after exhausting nonsurgical interventions. For this reason, knowledge of the various surgical procedures and postoperative outcomes will facilitate the clinician’s role as patient educator. Lavage and Debridement. Arthroscopic lavage and debridement is the least invasive surgical intervention. The risks of arthroscopy and lavage are low, but evidence140 has suggested that arthroscopic debridement is no better than conservative treatment in patients with PFP. Kettunen et al141 used the AKPS to compare 5-year outcomes for individuals with chronic PFP who were treated with knee arthroscopy and an 8-week home exercise program with those who only performed the home exercise program. All patients, regardless of intervention, showed meaningful improvements in pain (greater than 2-cm decrease in the VAS scores during stair ambulation and sit-to-stand transfer) and function (16- and 12-point improvements in AKPS scores for those who underwent arthroscopy or exercise only, respectively). No between-groups differences existed in VAS and AKPS scores, which suggested that arthroscopy did not provide any additional long-term beneﬁt over exercise alone. Lateral Retinacular Release. Lateral retinacular release (LRR) is another intervention used to address the tight lateral retinacular structures thought to contribute to PFP. The decision to perform an LRR requires special attention to the pain source, which may originate from excessive lateral patellar compression, lateral patellar instability, or articular cartilage damage. Panni et al60 evaluated changes in Lysholm scores at a minimum 5-year follow-up period (range ¼ 5–12 years) in patients who underwent LRR for either excessive lateral patellar compression or patellar instability. Although all patients reported signiﬁcant improvements, 70% of those with excessive lateral patellar compression described satisfactory results, compared with 50% of those with patellar instability or signiﬁcant articular cartilage damage (or both). These ﬁndings agreed with the results of others59,61,64,65 who recommended LRR for patients with PFP resulting from excessive lateral patellar tilting and no evident patellar instability or grade III or IV articular cartilage changes. Lateral Retinacular Lengthening. A potential complication after LRR is the development of medial patellar instability, leading some surgeons to perform lateral retinacular lengthening (LRL). The rationale is to reduce tension in the lateral retinaculum or reduce articular cartilage loading resulting from the tight lateral structures (or both) by lengthening the tissues rather than releasing them altogether. Pagenstert et al61 prospectively followed patients over a 2-year period to compare outcomes in those with excessive lateral patellar compression but no instability who underwent open LRR or open LRL. Patients who underwent open LRL demonstrated higher Lysholm scores and experienced no medial patellar subluxation. They also exhibited less quadriceps atrophy (deﬁned as a 2-cm difference in quadriceps girth) than those who underwent LRR. These ﬁndings provided preliminary evidence for the superiority of open LRL for patients with lateral patellar compression. Realignment Procedures. In some patients, joint or limb malalignment cannot be corrected by functional training. bearing quadriceps-strengthening exercises.145 This ﬁnding is limited in scope but corroborates well with the information in this position statement describing quadriceps weakness and tightness as risk factors. However, addressing mechan- ical risk factors involving the hip and knee during running and landing activities may beneﬁt a prevention program. Future studies are needed to make this determination. Regarding rehabilitation, a multimodal approach with a particular emphasis on active interventions is recommend- ed.29 Early hip-strengthening exercise appears to be an important component and should be combined with pain- free quadriceps exercises and movement retraining.48,71,127 The key consideration is that exercise should not cause further patellofemoral joint irritation. Although not indi- cated for all patients, a certain cohort may beneﬁt from passive interventions such as patellar taping and foot orthoses.29,101,139 These recommendations highlight the ongoing need to identify patient subgroups who may beneﬁt from targeted interventions and further advance our knowledge for managing this common, yet complex knee problem.97,146 or both. This ACKNOWLEDGMENTS We gratefully acknowledge the efforts of Michael J. Callaghan, PhD, MPhil, MCSP; Natalie Collins, PhD; Stephen D. Halverson, MA, LAT, ATC, CSCS; Karrie Hamstra-Wright, PhD, ATC; Brian Noehren, PhD, PT, FACSM; and the Pronouncements Committee in the preparation of this document. FINANCIAL DISCLOSURES Lori A. Bolgla, PhD, PT, MAcc, ATC; Michelle C. Boling, PhD, LAT, ATC; Kimberly L. Mace, DAT, ATC; and Michael J. DiStefano, MA, ATC, PES, CSCS have no disclosures to report. Donald C. Fithian, MD is a consultant for Breg, Inc (Carlsbad, CA). Christopher M. Powers, PhD, PT, FACSM, FAPTA, has a license agreement with DJ Orthopedics (DJO Global, Vista, CA) and is on the Scientiﬁc Advisory Board for Alter G, Inc (Fremont, CA). average of DISCLAIMER The NATA and NATA Foundation publish position state- ments as a service to promote the awareness of certain issues to their members. The information contained in the position statement is neither exhaustive nor exclusive to all circum- stances or individuals. Variables such as institutional human resource guidelines, state or federal statutes, rules, or regulations, as well as regional environmental conditions, may impact the relevance and implementation of those recommendations. The NATA and NATA Foundation advise members and others to carefully and independently consider each of the recommendations (including the applicability of same to any particular circumstance or individual). The position statement should not be relied upon as an independent basis for care but rather as a resource available to NATA members or others. Moreover, no opinion is expressed herein regarding the quality of care that adheres to or differs from the NATA and NATA Foundation position statements. The NATA and NATA Foundation reserve the right to rescind or modify its position statements at any time. provide a REFERENCES 1. Rathleff MS, Skuldbol SK, Rasch MN, Roos EM, Rasmussen S, Olesen JL. Care-seeking behaviour of adolescents with knee pain: a Journal of Athletic Training 831 19. Rathleff MS, Rathleff CR, Crossley KM, Barton CJ. Is hip strength a risk factor for patellofemoral pain? A systematic review and meta- analysis. Br J Sports Med. 2014;48(14):1088. (LOE: 1) 20. Herbst KA, Barber Foss KD, Fader L, et al. Hip strength is greater Dev. 2011;12(2):157– in athletes who subsequently develop patellofemoral pain. Am J Sports Med. 2015;43(11):2747–2752. (LOE: 2) 21. 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