Knee Notes - Complete PDF

Knee Thursday, October 3, 2024 10:11 AM - Functional anatomy ○ Innervation ▪ Knee joint innervated by L3-S1 nerve roots ○ Femur ▪ Femoral shaft is in oblique alignment with lower leg □ This produces a physiological valgus angle, approx...

Knee Thursday, October 3, 2024 10:11 AM - Functional anatomy ○ Innervation ▪ Knee joint innervated by L3-S1 nerve roots ○ Femur ▪ Femoral shaft is in oblique alignment with lower leg □ This produces a physiological valgus angle, approximately 170-175o ▪ On a lateral view, medial femoral condyle is more inferior to the lateral femoral condyle □ Recall from imaging II lateral view of knee ○ Patella ▪ Largest sesamoid bone in body ○ Ligaments ▪ Note: Injuries most commonly occur when ligs. are in their most taut state ▪ Injury triad □ ACL + MCL + medial meniscus This is due to some similar actions & their locations since the MCL is connected to the medial meniscus ▪ ACL □ Location Attached from anterior part of tibia Moves posterior & superior to the lateral intercondylar wall of the femur ◊ i.e. the medial surface of the lateral femoral condyle □ Action Checks anterior displacement and extension of the tibia □ Injury MC lig. for injury Becomes taut in knee flexion ▪ PCL □ Strongest of the knee lig. □ Location Attached from posterior part of the tibia Moves anterior & superior to the media intercondylar wall of the femur ◊ i.e. the lateral surface of the medial femoral condyle □ Action Checks posterior displacement and internal rotation of the tibia When knee extended, provides some M->L stability of the tibia □ Injury Becomes taut in knee extension ▪ MCL □ Location Attaches proximal medial tibia to the medial side of the medial femoral epicondyle □ Action Checks knee extension, abduction, external rotation Checks some anterior displacement of the tibia □ Injury Becomes taut in knee extension, abduction, external rotation Due to its action, injury to MCL commonly occurs during ACL injuries ▪ LCL □ Location Attaches proximal part of fibular head to the lateral side of the lateral femoral epicondyle Popliteus tendon runs between the LCL and the bony surfaces □ Action Checks knee extension, adduction, external rotation □ Injury Becomes taut in knee extension, adduction, external rotation Exam 1 Page 1  ▪ ○ Menisci ▪ Shock absorbers, made of fibrocartilage, is lubricated to keep nourishment ▪ Ortho test that checks compression & rotation is used to assess injuries ▪ Medial meniscus □ Semilunar shape □ Outside part Larger, wrapping around the medial side of the medial femoral condyle □ Posterior part Larger than anterior side, is able to take more weight with knee flexion ▪ Lateral meniscus □ Almost full circle shape ○ Muscles ▪ □ Take note of the highlighted muscle actions on the image to the right, will be tested on these main ones □ Table on the left is for your reference to differentiate hip action movements & knee action movements ▪ Hamstring muscles □ From medial to lateral -> semimembranosus (deep), semitendinosus (superficial), biceps femoris long head, biceps femoris short head ▪ Plantaris □ Can only flex and internally rotate during open-chain exercises due to its size ▪ Pes anserinus tendons □ Common tendon insertion site on the medial tibia □ Components Exam 1 Page 2  □ Components Tendons of the semitendinosus, gracilis, and sartorius □ Function Helps prevent external rotation, abduction, and anterior displacement of the tibia (also the semimembranosus tendon, but is not considered a part of the 'pes anserinus') ○ Bursa ▪ Functions □ Helps prevent friction by separating the tendons from ligaments and muscles ▪ Suprapatellar bursa □ Above the patella ▪ Prepatellar bursa □ In front of patella, superficial to patellar lig. □ Can get inflamed during prolonged kneeling ▪ Infrapatellar bursa □ Below the patella, superficial to patellar lig. ▪ Baker's cyst □ Posterior aspect of knee, at the medial head of gastrocnemius near its origin □ - Biomechanics ○ ○ ○ Actions ▪ General □ Reacts to rotational forces □ Absorbs shock □ Propulsion ▪ Extension □ Quadriceps ▪ Flexion □ Hamstrings, gracilis, sartorius ○ Tibiofemoral - knee joint Exam 1 Page 3 ○ Tibiofemoral - knee joint ▪ Rotation forces □ Mostly a hinge joint There is slight rotation when knee is not in closed-packed position ▪ Screw-home mechanism □ Open-chain, i.e. if we immobilize the femur As you go further into knee extension, the tibia externally rotates under the femur □ Closed-chain, i.e. if we immobilize the tibia As you go further into knee extension, the femur internally rotates over the tibia □ Gate mechanics (for your own info for now) Tibia internally rotates during swing phase Tibia externally rotates during stance phase ▪ Absorption □ Congruency, i.e. Menisci Shape ◊ Medial  Semilunar, is smaller than lateral meniscus ◊ Lateral  Almost full circle, is larger than medial meniscus ◊ Thicker on the periphery, i.e. the outsides of the menisci Function ◊ Shock absorption ◊ Increase surface area ◊ Increases stability □ Shock Stress = force / area ◊ If we increase area = less stress ◊ If we decrease force = less stress □ Pain Menisci have mechanoreceptors & proprioceptors ◊ Mechanoreceptors help orient where our knee is in space ◊ Lateral parts of the menisci have the most proprioceptors, and is very painful if you have a tear there ▪ Propulsion □ Important for gait, i.e. hemiplegic □ Muscular component Eccentric ◊ Muscle lengthens under tension  i.e. still holding tension/ contracting, but weight over-powering -> lengthening 'under tension' Concentric ◊ Muscle shortens under tension  i.e. able to do a bicep curl ○ Patellofemoral ▪ During knee flexion, patella sinks down to the tibial tuberosity □ This lengthens the lever arm, increasing force output ▪ Q angle □ Line through center of patella compared to the shaft of the femur up to ASIS □ ~10-15o □ Is slightly larger in females due to pelvis shape ▪ Position □ Alta = high □ Baja = low Exam 1 Page 4  ▪ ○ Superior tibiofibular ▪ The ankle joint mostly influences this joint ▪ Ankle dorsiflexion □ Fibula internally rotates and rises ▪ Ankle plantarflexion □ Fibular externally rotates and lowers ▪ Ankle inversion □ Fibular head moves anterior ▪ Ankle eversion □ Fibular head moves posterior - Evaluation ○ General info ▪ Trauma is common in the knee ▪ When assessing the knee, need to assess the pts hip and ankle as well ▪ Referred pain from LBP can cause some certain discomfort of the knee ○ Collateral ligaments ▪ Usually due to trauma ▪ MCL injury □ MOI External rotation twisting + flexed knee Valgus blow, i.e. L->M blow □ Higher likelihood of medial meniscus injury, as well as ACL ▪ LCL injury □ MOI Internal rotation twisting + hyperextension Varus blow, i.e. M->L blow □ Can cause fibular head avulsion due to LCL connection ▪ ACL injury □ MOI Forced internal rotation of femur on fixed tibia + knee abduction & flexion ◊ i.e. making a cut in football/ soccer Knee hyperextension + valgus stress ◊ i.e. hard landing leading to excessive hyperextension with a firmly planted foot on the ground ◊ In hyperextension, the femur rolls posterior in relation to a fixed tibia, stretching the ACL Sudden eccentric quad contraction ◊ i.e. sudden stopping from a sprint can cause a large "pull" of the tibia anteriorly in relation to the femur Exam 1 Page 5  □ □ Symptoms Loud pop Swelling comes quick and aggressive □ Management Surgery depends on severity, age, activity level MRI Stabilization program of hamstrings/ proprioceptive training ▪ PCL injury □ MOI Forced external rotation of femur on fixed tibia + knee abduction & flexion ◊ Similar sports as ACL Impact mechanisms ◊ Impact on a flexed tibia  Causes the tibia to drive posterior in relation to the femur ◊ i.e. in a car accident □ Symptoms Loud pop Swelling comes quick, less than ACL but can include increased bruising □ Management Same as ACL, but surgery here is normally less necessary than ACL Stabilization program of quadriceps/ proprioceptive training ○ Menisci ▪ MOI □ Rotation with violent extension □ Potentially some compression ▪ Symptoms □ Issues with knee locking in flexed position until forced into extension □ Knee "giving away" □ Swelling ▪ Management □ Stable tears Tears that don't require surgery Can heal with rest & proper intervention □ Unstable tears If no intervention, it will tear more and cause greater issues □ Protected weight-bearing + protective ROM training ○ Patellofemoral issues ▪ Patellar tracking □ Relationship b/w vastus medialis & lateralis ▪ Can lead to expedited OA/ chondromalacia patella ▪ Chondromalacia patella □ Erosion of posterior cartilage of patella Exam 1 Page 6  □ Erosion of posterior cartilage of patella □ Causes Constant grinding of posterior cartilage due to improper tracking Increased Q angle Inflammation of infrapatellar bursa □ Management Bracing, taping, strengthening ▪ Patellar tendinitis □ Anterior knee pain with explosive movements □ Causes Repetitive stress to tendon □ Management Resting, isometric holds of knee extension Exam 1 Page 7