Biomechanics of gait analysis book Dr-هبسطهالك.pdf

Biomechanics of Gait analysis  Content ❑Gait Cycle ▪ Definition ▪ prerequisites ▪ phase of gait ▪ Intervals of Gait ❑ Gait analysis 1- kinematic analysis 2- kinetic analysis ❑ Pathomechanics of gait #Biomechanics-of-gait Lecture 1 ...

Biomechanics of Gait analysis  Content ❑Gait Cycle ▪ Definition ▪ prerequisites ▪ phase of gait ▪ Intervals of Gait ❑ Gait analysis 1- kinematic analysis 2- kinetic analysis ❑ Pathomechanics of gait #Biomechanics-of-gait Lecture 1  Content of lecture Gait cycle 1-Definition 2-Prerequisites 3-Phases of Gait Stance phase Swing phase #Biomechanics-of-gait 1-Definition of normal gait ❑Physiological Definition: It is a mechanism which depends upon closely integrated action of the subjects, bones, muscles and nervous system (including peripheral and central nervous system) The degree of integration determines the different gait patterns. Any defect of any part of them or all of them will lead to pathological gait. ❑ Mechanical definition: It is a form of bipedal locomotion as there is an alternating action between lower extremities. One leg is in touch with the ground for restraining, supporting and propulsion. The other leg is in swing phase for creating a new step forward. So, gait is the result of a series of rhythmic alternating movement of arms, legs, and trunk which create forward movement of the body. #Biomechanics-of-gait 2-Prerequisites of gait: 1. The ability to support upright position. (the ability to maintain head, arms, and trunk HAT against gravity) 2. The ability to maintain balance in an upright position during static and dynamic situation. 3. The ability to develop or create new step forward N.B: HAT constitute 75% of total body weight. #Biomechanics-of-gait  Phases of Gait cycle Gait cycle: is used to describe the complex activity of walking, or our gait pattern. This cycle describes the motions from initial placement of the supporting heel on the ground to when the same heel contacts the ground for a second time. At normal adult walking speeds, one cycle lasts 1 second and has a length of 1.4 meters. During one gait cycle, each extremity passes through two phases, a single stance phase and a single swing phase. #Biomechanics-of-gait Phases of Gait cycle #Biomechanics-of-gait  Phases of Gait cycle Stance phase Swing phase 60 % 40 % #Biomechanics-of-gait  Stance Phase Is defined as the interval in which any part of the foot of one extremity is in contact with the ground (60% of the gait cycle) and it ends when the reference foot lifts off the ground. So, it is called “the supporting phase” or “weight bearing phase”. #Biomechanics-of-gait Stance Phase is divided into 5 phases: 1- Initial contact (heel strike): Initial contact is an instantaneous point in time only and occurs the instant the foot of the leading lower limb touches the ground. This phase occurs at about 0%- 2% of GC. The heel is usually the foot section that makes initial contact, but other parts of the foot may contact the ground first in the presence of some pathologic conditions. #Biomechanics-of-gait 2- Loading response (flat foot): The loading response phase occupies about 2%-10% of the GC and constitutes the period of initial double stance. During loading response, the foot comes in full contact with the floor, and body weight is fully transferred onto the stance limb. During this phase, the body’s impact forces with the ground are absorbed. 3- Mid stance: Mid-stance represents the first half of single support, which occurs from the 10%- 30% of the GC. It begins when the contra-lateral foot leaves the ground and continues as the body weight travels along the length of the supporting lower limb until it is aligned over the forefoot. In this phase the body’s COM moves directly over the foot. #Biomechanics-of-gait 4- Terminal stance (heel off): Terminal stance constitutes the second half of single-limb support. It begins with heel of the reference foot rise and ends when the contra-lateral foot contacts the ground. Terminal stance occurs from the 30%- 50% of GC. 5- Pre-swing (toe off): Pre-swing occurs when only the toe of the reference limb is in contact with the ground. This phase called weight release or weight transfer. This phase occurs from 50%- 60% of GC. It is the terminal double stance interval #Biomechanics-of-gait  Swing phase Is defined as the interval in which the foot of the reference limb is not in contact with the ground (40% of the gait cycle) and it ends just prior to heel strike of the same extremity. It denotes the time when the foot is in the air, so it is called “non- weight bearing period”. The swing period primarily is divided into three phases: Initial swing, mid-swing and terminal swing. #Biomechanics-of-gait 1- Initial swing (acceleration): It is the period from toe of the reference limb leaves the ground to the mid-swing of the reference limb. This phase is from 60%-73% of GC. 2- Mid-swing: It is period when the reference limb passes directly under the body. The reference limb reaches vertical tibial position just before the end of mid-swing. This phase is from 73%-87% of GC. 3- Terminal swing (deceleration): It is period from the end of mid-swing to the point just before initial contact. The knee is extending in preparation for new heel strike. This phase is from 87%-100% of GC #Biomechanics-of-gait Thank You #Biomechanics-of-gait Lecture 2  Content Intervals of gait cycle Functional Tasks of Gait Introduction Kinematic analysis #Biomechanics-of-gait  Gait intervals Double limb support Single limb support (20% of GC) (40% of GC) 1-Initial double stance (IDS) 10% 2-Terminal double stance (TDS) 10% #Biomechanics-of-gait Initial double stance: is the period when both feet are in contact with the ground. One foot is in initial contact and loading response and other foot is in pre-swing. Terminal double stance: in late stance, the ipsilateral foot is in pre-swing and contralateral foot is in initial contact and loading response ❑ As velocity increases, double-limb support time decreases. Running constitutes forward movement with no period of double-limb support. ❑ In normal walking, initial double stance takes up about 10% of GC, also the terminal double stance takes up to 10% of GC. #Biomechanics-of-gait Single limb support SLS: is the period when only one foot is in contact with the ground (mid stance and terminal stance). In walking, this is equal to the swing phase of the other limb. It takes up to 40% of GC. II- Swing phase has one interval as one foot is not in contact with the ground and it takes up to 40% of gait cycle #Biomechanics-of-gait  Functional Tasks of Gait 1. weight acceptance 2. single limb support 3. limb advancement ❑ The stance phase plays a role in all three of these basic tasks, each of its sub- phases contributing to varying degrees. Initial contact and loading response are the two sub-phases primarily responsible for weight acceptance. ❑ Single limb stance occurs at mid-stance and is the time when balance during ambulation is most precarious. The body’s center of mass has shifted laterally and is centered over only one supporting limb at this time. #Biomechanics-of-gait Limb advancement creates forward motion of the body and includes the stance sub-phases of terminal stance and pre-swing; these sub-phases provide propulsive forces to move the limb forward and thereby move the body forward. The stance sub-phases utilize effective force absorption and efficient energy expenditure to accomplish these tasks. The swing phase is concerned with only one of the three fundamental tasks: limb advancement. Limb advancement during the swing phase requires sufficient clearance of the foot from the floor. The limb performs this activity during the first half of swing and prepares for initial contact during the latter half of swing. During the first two sub-phases of the swing phase, initial swing and midswing, the limb flexes at the hip, knee, and ankle to functionally shorten the limb so the foot clears the floor. The knee then begins rapid extension in terminal swing to lengthen the limb; this motion increases step length and forms a rigid limb in preparation for stability at initial contact #Biomechanics-of-gait  Analysis of gait Kinematic analysis Kinetic analysis #Biomechanics-of-gait Kinematic analysis Kinematics is the science of motion. In human movement, it is the study of the positions, angles, velocities, and accelerations of body segments and joints during motion. It classified into 3 categories: 1. Distance and time variables 2. Joint angles from sagittal and frontal plane for upper and lower limbs 3. Determinants of gait #Biomechanics-of-gait 1- Distance and time variables Step length: It is the linear distance between the initial contact of one foot to the initial contact of the opposite foot. Values for normal adult’s step length are: 64 cm average for women, 73 cm average for men, and the overall average is 70.5 cm. #Biomechanics-of-gait Stride length: It is the linear distance between two successive foot contact of the same limb. It consists of two step lengths, left and right, It is usually measured from the midpoint of heel Values for normal adult’s stride length are: 128 cm average for women, 146 cm average for men the overall average is 141 cm. However, stride length is not always twice the length of a single step because right and left steps may be unequal. #Biomechanics-of-gait Stride width: It is the horizontal linear distance between the midpoint of the heel of one foot and the same point of the other foot. Step width measures typically between 2.5 to 12.5 cm for adults with the average of 8 cm; this standard does not hold true in some pathological conditions. Degree of toe out: It is the angle formed by each foot’s line of progression and a line intersecting the center of heel and the second toe. Out- toeing of about 7° is typical in mature adults. The degree of toe out decreases as the speed of walking increases in normal adults. #Biomechanics-of-gait 2-Time variables (Temporal parameters) Step time: it is time spent during single step between heel strike of one leg and heel strike of the other leg. Stride time: It is the time interval between successive instant of foot floor contact of the same foot. (i.e. it is the amount of time it takes to complete one stride). Stance time: It is the time that passes during the stance phase of one limb in a gait cycle. Swing time: It is the time while the foot is not in contact with the floor. (0.4 sec.) Single limb time: it is the time when only one limb is on contact with the supporting surface. Double limb time: it is time spent with both feet on the ground during one gait cycle. It decreases as the speed of walking increases. #Biomechanics-of-gait Swing / stance ratio: It is the ratio between swing time and stance time Cadence: It means number of steps per minute. (110 steps /min) Slow: 60 – 70 Steps / min. Medium: 80 – 90 Steps / min. Fast: 120 Steps / min. increased number of steps at a shorter step length constant distance duration of the double limb increased cadence stance decreases Speed: It is distance / time. - In male: 89 meter/min. - - In female: 74 meter/min. #Biomechanics-of-gait Thank You #Biomechanics-of-gait Lecture 3  Measurement of joint angles Sagittal Plane kinematics Hip Knee Ankle #Biomechanics-of-gait Function of pelvis during gait providing both stability and mobility to upper and lower extremities The pelvis offers a stable base of support for the lower limb and HAT but it also must allow for the contributions of thoracic and lumbar spine motions the pelvis must be stable enough to transmit weight as it transfers from one limb to the other, and it also needs to move the acetabulum in a favorable position for hip motion In the sagittal plane, the pelvis remains relatively level, demonstrating an average anterior-posterior tilt excursion of only about 3° during the gait cycle #Biomechanics-of-gait Two full cycles of sinusoidal motion occur with each step; the pelvis reaches initial contact in a near-neutral position and moves through midstance in a slightly posteriorly tilted position. By the end of midstance when the hip begins moving into extension, the pelvis tilts anteriorly just slightly. By the time the limb reaches preswing, the pelvis tilts posteriorly again. During swing, the pelvis first completes its posterior tilt and then tilts anteriorly from initial to midswing, and in terminal swing it moves toward a posterior tilt in preparation for landing once again. #Biomechanics-of-gait Hip joint Stance phase Swing phase IC LR MST TST PSW ISW MSW TSW 30 25 0 10 0 20 30 30 flexion flexion hyperextenstion flexion flexion flexion #Biomechanics-of-gait These typical sagittal plane arcs that occur at 10° of hyperextension (at terminal stance) and at 30° of flexion (at midswing) occur during normal walking speed but are slightly higher in fast walking. Tst : hyperextension arc 10 acts to transfer weight to contralateral limb Msw : flexion arc 30 acts to clear foot from the ground Clinical note: because pelvis and lumbar spine motions are mechanically linked at sacroiliac joint, exaggerated pelvic tilting during walking may increase the stress at lumbar spine. These stresses could eventually irritate the structures within this region resulting in low back pain #Biomechanics-of-gait Knee Joint Stance phase Swing phase IC LR MST TST PSW ISW MSW TSW 5 15-20 0 or 5 0 35-40 40-60 60-65 0 flexion flexion flexion flexion flexion flexion #Biomechanics-of-gait LR : the 1st arc of knee flexion : act as shock absorption TSt : the 1st arc of knee extension : act to transfer weight to contralateral limb MSw : the 2nd arc of knee flexion : act to clear foot from ground TSw : the 2nd arc of knee extension : act for preparation for new step #Biomechanics-of-gait Ankle Joint Stance phase Swing phase IC LR MST TST PSW ISW MSW TSW 0 15 5-10 10 20-30 10 0 0 neutral PL DF DF PF PF #Biomechanics-of-gait LR: 1st planter flexion arc :act as shock absorption TSt: 1ST dorsiflexion arc : act to transfer weight to contralateral limb PSw: 2nd planter flexion arc : act for propulsion MSw: 2nd dorsiflexion arc : act to clear foot from ground and preparation for new step #Biomechanics-of-gait Summary Stance phase Swing phase Phases IC LR MST TST PSW ISW MSW TSW HIP 30 25 0 10 0 20 30 30 flexion flexion hyperextenstion flexion flexion flexion KNEE 5 15-20 0 or 5 0 35-40 40-60 60-65 0 flexion flexion flexion flexion flexion flexion ANKLE 0 15 5-10 10 20-30 10 0 0 neutral PL DF DF PF PF #Biomechanics-of-gait Thank You #Biomechanics-of-gait Lecture 4  Frontal plane kinematics pelvis Hip Knee Ankle #Biomechanics-of-gait Pelvis ❑ The pelvis tilts laterally in the frontal plane about 8° on each side. In unilateral stance (midstance) , the pelvis of the swing leg (opposite leg) tilts laterally downward about 8°. This lateral drop occurs on the swing leg since the stance leg adducts. Function of lateral pelvic tilting 1- It puts the hip abductor muscles of the stance leg on a slight stretch, thereby putting them at an improved length tension advantage 2-It reduces the rise of the center of mass of the swing leg. This reduction in the limb’s COM elevation was initially thought to be important in decreasing energy expenditure. #Biomechanics-of-gait Hip Joint At initial contact, the hip is adducted to about 10° and continues to adduct another 5° during loading response, serving to puts the gluteus medius on the stance side on slight stretch. This position places the gluteus medius on stretch so it may generate the forces needed to stabilize and hold the contralateral pelvis level during unilateral stance. From midstance through terminal stance, the thigh moves into a relatively neutral position. The hip abducts about 5° during swing phase to assist in clearing the foot from the floor and returns to neutral as it approaches the end of terminal swing. #Biomechanics-of-gait Summary 1. IC : add 10 2. LR : add 15 3. MST : add / this help with pelvic lateral tilting downward to stretch gluteus medius , so it may generate a force needed to stabilize and hold reference limb in mst 4. TST : move from add to abd 5 5. PSW : Abd 5 6. ISW : Abd 7. MSW : neutral 8. TSW : in the end move to Add The hip abducts about 5° during swing phase to assist in clearing the foot from the floor and returns to neutral as it approaches the end of terminal swing. #Biomechanics-of-gait Knee joint At initial contact the knee is in slight abduction and moves to its maximum of about 3° of abduction during initial contact. During the swing phase, the knee moves into adduction to a maximum of about 8° Why total Abd – Add of knee is minimal ? Because stable collateral ligaments supporting the joint ❖Medial collateral ligament ❖Lateral collateral ligament #Biomechanics-of-gait Ankle joint and Foot 1. Subtalar Joint Subtalar joint motions of inversion and eversion occur during gait. The subtalar joint is in slight inversion at initial contact and immediately moves into eversion after making contact with the ground. The subtalar joint rapidly moves through to its maximum range of eversion, about 5°, after loading response and by the time the limb is in early midstance. At midstance, the subtalar joint begins moving toward inversion. By preswing, it is at its maximum inversion position, approximately 8° to 11°. #Biomechanics-of-gait 1.IC : slight inversion 2.LR : eversion 5 3.MST : first half / maximum eversion second half / move into inversion 4.TST : inversion 5.Psw : maximum inversion 8 to 11 During the swing phase, the subtalar joint returns to neutral and is in slight inversion by the time the limb is in terminal swing. #Biomechanics-of-gait 2- midtarsal joint ❖Talonavicular joint ❖Calcaneocuboid joint The two joints comprising the midtarsal joint, the talonavicular and calcaneocuboid joints, each have approximately 11° to 15° of total motion in the frontal plane during normal gait cycle. LR : the midtarsal joint flattens to absorb impact forces and to allow the entire foot to touch the ground. Once in midstance, the arch elevates In Tst & Psw : the forefoot joints into more congruent positions #Biomechanics-of-gait  Transverse plane kinematics pelvis Hip Knee Ankle #Biomechanics-of-gait  pelvis Movement : rotate anterior & rotate posterior ❖ During swing phase : pelvis rotate anterior 4 ❖ During stance phase : pelvis rotate posterior 4 Total pelvic movement in transverse plane 8 Pelvic rotation increases 10 to 20 with increased speed Maximum amount of anterior pelvic rotation occurs at initial contact in concert with maximum hip flexion (30°) #Biomechanics-of-gait Hip joint At initial contact, the hip is in slight lateral rotation, Immediately after loading response, however, the hip medially rotates and maintains a medially rotated position through loading response and midstance until the hip moves into extension. From midstance to terminal stance, the hip moves to neutral rotation and continues into lateral rotation at preswing. Isw & Msw : neutral position Tsw : slight lateral rotation Peak hip medial rotation occurs at the end of loading response maximum lateral rotation occurs at the end of preswing total hip rotation ranges between 8° and 14° for normal adults. #Biomechanics-of-gait Knee joint Throughout the entire gait cycle, the knee rotates a total of about 10° to 20°. Of this total rotation, the femur rotates on the tibia 6° to 7° medially, and laterally and the tibia rotates 8° to 9° in each direction. At initial contact, the knee is in slight lateral rotation (tibia relative to the femur) but then medially rotates as the limb accepts the weight. As the foot pronates during loading response, the tibia medially rotates about 8°, allowing the knee to flex. After midstance, the femur and tibia begin to rotate laterally in the transverse plane through preswing. When body weight is shifted to the other leg in preswing, the tibia is led into lateral rotation by the supinated foot and the limb moves into swing. During swing, the thigh, knee, and leg move toward and into medial rotation until terminal swing, when they laterally rotate in preparation for initial contact. #Biomechanics-of-gait Ankle and Foot Midfoot rotation in the early part of the stance phase is essential for shock absorption and allows the foot to adapt to uneven surfaces as the foot moves into loading response. At midstance, the tarsal joints rotate into supination to transform the foot to a rigid lever that permits propulsion of the body forward as the foot pushes against the ground. #Biomechanics-of-gait  Trunk and upper extremity kinematics ▪ The trunk and upper extremities play an important role in maintaining balance and minimizing energy expenditure during gait Head and Trunk ▪ During normal gait the head and trunk travel as one unit. Throughout the gait cycle the head, arms, and trunk (HAT) and center of gravity (COG) deviate from the mean line of progression in all three planes. ▪ Displacement pattern is a sinusoidal curve. So, the HAT and COG displace twice in upward direction and twice in downward direction in sagittal plane. ▪ The displacement in lateral direction in horizontal plane is once ipsilateral on right lower limb and once contralateral on left lower limb. #Biomechanics-of-gait ▪ The peak downward deviation occurs in loading response and in preswing. ▪ The peak upward deviation occurs in midstance and late midswing. #Biomechanics-of-gait Shoulder joint kinematics ✓ The hip (femur) moves toward extension, the ipsilateral shoulder (humerus) moves toward flexion, and vice versa. ✓ At heel contact, the shoulder is in its maximally extended position of approximately 25º beyond the neutral position. The shoulder then progressively rotates forward to reach a maximum of 10º of flexion by 50% of the gait cycle. ✓ In the second half of the gait cycle, as the ipsilateral hip moves forward toward flexion, the shoulder extends to return to 25º of extension by the next heel contact. ✓ the amplitude of shoulder movement increases with greater speed. ✓ The major function of arm swing is to balance the rotational forces in the trunk. ✓ Flexion of shoulder and elbow : propulsive force during gait #Biomechanics-of-gait Elbow joint kinematics The elbow is normally in approximately 20º of flexion at heel contact. As the shoulder flexes in the first 50% of the gait cycle, the elbow also flexes to a maximum of approximately 45º. In the second half of the gait cycle, as the shoulder extends, the elbow extends to return to 20º of flexion #Biomechanics-of-gait Thank You #Biomechanics-of-gait Lecture 5  Kinetic analysis of gait It is the analysis of forces acting on body during gait. Forces of gait include internal and external forces. ❑External forces are: 1. Inertia 2. Gravity 3. ground reaction force (GRF). ❑ Internal forces: 1. primarily by muscles 2. The ligaments 3. Tendons 4. joint capsules #Biomechanics-of-gait External forces The gravitational force acts directly downward through the COG of the body at which the body weight is represented by a line (line of gravity LOG). ✓ If the LOG passes directly through a joint axis, no gravitational torque is created around that joint. ✓ If the LOG passes at distance away from the joint axis, a gravitational torque is created. This torque will cause motion of the body segments around that joint axis. ✓ If the LOG is located anterior to the joint axis, the torque will cause anterior motion of the proximal segment. If the LOG located posterior to the joint axis, the torque will cause a motion in the posterior direction. #Biomechanics-of-gait ✓ The gravitational torque is opposed by a counterbalancing torque created in the opposite direction. This counterbalancing torque is done mainly by active muscular tension. Passive tension by ligaments and joints capsules may assist in this counterbalance. Pathway of GRFV The analysis includes the location of the GRFV in relation to joint axis during stance phase form sagittal plane and frontal plane #Biomechanics-of-gait Sagittal plane IC LR Mst Tst Psw A A P P P Hip flexion flexion extension extension extension A P A A P Knee extension flexion extension extension Flexion P P A A A Ankle planter planter dorsiflexion dorsiflexion dorsiflexion flexion flexion #Biomechanics-of-gait #Biomechanics-of-gait Frontal plane IC LR Mst Tst Psw Hip L / abd M / add M / add M / add L / abd Knee L / abd M / add M / add M / add neutral Ankle neutral L/ L/ M/ neutral eversion eversion inversion #Biomechanics-of-gait #Biomechanics-of-gait Internal forces Internal forces which are developed during gait are created primarily by the muscles. The ligaments, tendons, joint capsules and bony components assist the muscle by resisting, transmitting and absorbing forces. To be in a state of equilibrium during gait, the internal and external forces should be balanced and the sum of all forces acting on the body and its segment must be equal to zero. For this reason, the moment created by GRFV must be counteracted by muscle activity and other soft tissue structures. #Biomechanics-of-gait How to know the acting muscle and type of muscle contraction during gait ? 1- Identify the pathway of GRFV and the moment resulting from this passage. If the vector is anterior to the joint so the muscle or other structure in the opposite direction is acting to counterbalance the effect of gravity. 2- Determine the desired joint motion in this sub phase of gait 3- if the joint motion occurs in one direction (e.g. flexion) and the acting muscle works in the opposite direction (extensors), the type of contraction is eccentric #Biomechanics-of-gait Example #Biomechanics-of-gait Effect of pathway of LOG #Biomechanics-of-gait Thank You #Biomechanics-of-gait Lecture 6 Sagittal plane kinetics #Biomechanics-of-gait #Biomechanics-of-gait General rules #Biomechanics-of-gait HIP joint ▪ Initial contact 1- GRFV pass anterior to hip joint 2- create flexion moment 3- desired movement : flexion 4- Eccentric contraction Stance phase Swing phase IC LR MST TST PSW ISW MSW TSW 30 25 0 10 0 20 30 30 flexion flexion hyperextenstion flexion flexion flexion #Biomechanics-of-gait ▪ Loading response 1- GRFV pass anterior 2- create flexion moment 3- desired movement : Extension 4- contraction of muscle : Concentric contraction of gluteus Maximus Increases activity of gluteus Maximus , decreases activity of hamstring muscle Stance phase Swing phase IC LR MST TST PSW ISW MSW TSW 30 25 0 10 0 20 30 30 flexion flexion hyperextenstion flexion flexion flexion #Biomechanics-of-gait ▪ Mid stance & terminal stance 1- GRFV pass posterior 2- create extension moment 3- desired movement : extension 4- eccentric contraction of iliopsoas , rectus femoris and tensor fascia lata ( hip flexors ) Stance phase Swing phase IC LR MST TST PSW ISW MSW TSW 30 25 0 10 0 20 30 30 flexion flexion hyperextenstion flexion flexion flexion #Biomechanics-of-gait ▪ preswing 1- GRFV pass posterior 2- create extension moment 3- desired movement : flexion 4- concentric contraction of flexors muscle Stance phase Swing phase IC LR MST TST PSW ISW MSW TSW 30 25 0 10 0 20 30 30 flexion flexion hyperextenstion flexion flexion flexion #Biomechanics-of-gait ▪ Initial swing: Hip flexors mainly iliopsoas, sartoruis, and gracilis contract concentrically to initiate swing phase. ▪ Midswing : Muscle action may be absent or minimal in flexors. ▪ Terminal swing: flexors activity stopped and hamstring and gluteus maximus contract eccentrically to control forward progression of lower limb. #Biomechanics-of-gait Knee joint ▪ Initial contact 1- GRFV pass anterior 2- create extension moment 3- desired movement : extension 4- muscle contraction - Concentric contraction of quadriceps muscle - Eccentric contraction of hamstring muscle to prevent hyperextension #Biomechanics-of-gait ▪ Loading response Function of eccentric contraction of quadriceps in LR ? 1- GRFV pass posterior 1- control amount of knee flexion 2- create flexion moment 2- prevent excessive knee flexion 3- desired motion : flexion 3- decelerate body 4- muscle contraction 4- shock absorption - Concentric contraction of hamstring muscle - Eccentric contraction of quadriceps muscle to control amount of knee flexion ( counterbalance of this motion ) #Biomechanics-of-gait ▪ Mid stance & Terminal stance 1- GRFV pass anterior , so create extension moment - Quadriceps muscle have relaxed so , knee extension stability provided by 1- strong ankle planter flexors muscles ( gastrocnemius – soleus ) provide stable tibia over which the femur continuous to advance ( indirect knee flexion ) 2- Passage of GRFV anterior to the axis of the knee provides a small passive extensor force. At the end of terminal stance, these mechanisms have the potential to create undesirable knee hyperextension. To avoid this, the popliteus and gastrocnemius provide a flexor action posteriorly. #Biomechanics-of-gait #Biomechanics-of-gait ▪ Preswing 1- GRFV pass posterior 2- create flexion moment Eccentric contraction of rectus femoris : prevent excessive of knee flexion ▪ The popliteus and gastrocnemius that initially were preventing knee hyperextension are free to initiate knee flexion to unlock knee. #Biomechanics-of-gait -Initial swing: Toe clearance from ground is essential which is obtained by concentric contraction of the short head of biceps femoris, gracilis, and sartorius muscles. -Midswing: No muscle action is needed and the limb advances by the effect of Momentum generated by the continuing hip flexion till 65º flexion. -Terminal swing: Concentric contraction of quadriceps is required to lift the weight of tibia and foot. Excessive knee hyperextension is prevented by eccentric contraction of hamstrings to control the forward motion of lower limb #Biomechanics-of-gait Ankle joint ▪ Initial contact 1- GRFV pass posterior 2- Create planter flexion moment 3- desired movement : neutral 4- concentric contraction in tibialis anterior muscle #Biomechanics-of-gait ▪ Loading response 1- GRFV pass posterior 2- create planter flexion moment 3- desired movement : planter flexion 4- eccentric contraction of tibialis anterior, Function ? 1- decelerate foot 2- control amount of planter flexion 3- prevent excessive planter flexion 4- shock absorption #Biomechanics-of-gait ▪ Mid stance 1- GRFV pass anterior 2- create dorsiflexion moment 3- desired motion : dorsiflexion 4- eccentric contraction of gastrocnemius muscle and soleus ( triceps surae ) muscle to control motion , to slow rate of tibial advancement #Biomechanics-of-gait ▪ Terminal stance 1- GRFV pass anterior 2- create maximum dorsiflexion 3- desired movement : dorsiflexion 4- strong eccentric contraction of triceps surae - Control tibial advancement - Prevent excessive dorsiflexion - Decelerate tibia on foot #Biomechanics-of-gait ▪ Preswing Planter flexors reduce their intensity of action. Their concentric contraction is enough to accelerate advancement of the unloaded limb. ▪ Initial swing and midswing : Toe clearance is essential so tibialis anterior, extensor digitorum longus, and extensor hallucis longus contract concentrically to move foot from planter flexed position at preswing to a position of neutral in midswing. Then they act isometrically to maintain the ankle in neutral position throughout the swing phase ▪ Terminal swing : There is isometric activation of pretibial group then at the end of swing phase there is increase in activity of these muscles to assure the ankle will be neutral for optimum heel contact in the upcoming stance phase. The most active one of these muscles is tibialis anterior #Biomechanics-of-gait #Biomechanics-of-gait Thank You #Biomechanics-of-gait Lecture 7 Frontal plane Kinetics #Biomechanics-of-gait Frontal plane kinematics of hip 1. IC : add 10 2. LR : add 5 3. MST : add / this help with pelvic lateral tilting downward to stretch gluteus medius , so it may generate a force needed to stabilize and hold reference limb in mst 4. TST : move from add to abd 5 5. PSW : Abd 5 6. ISW : Abd 7. MSW : neutral 8. TSW : in the end move to Add The hip abducts about 5° during swing phase to assist in clearing the foot from the floor and returns to neutral as it approaches the end of terminal swing. #Biomechanics-of-gait Hip joint During early stance the HAT shift laterally over the supporting limb which creates demands for lateral stability at the hip joint. This lateral stability provided by gluteus medius, glueus maximus and tensor fascia lata. Initial contact 1- GRFV pass lateral 2- create abduction moment 3- desired movement : adduction 4- concentric contraction of adductor Magnus and longus muscle -Initial contact: The GRFV passes lateral to hip joint and creates abduction moment which is counterbalanced by activity of adductor Magnus mainly. The motion required from the hip is adduction so the adductor contract concentrically. The pelvis drops slightly. #Biomechanics-of-gait  Loading response The GRFV lies medial to hip joint creating adduction moment that is counterbalanced by hip abductors contraction to control the lateral pelvic drop on the swing limb (5º). The desired motion is hip adduction and the contraction is eccentric. The main active muscles are gluteus medius, gluteus maximus, and tensor fascia lata. 1- GRFV pass medial 2- create adduction moment 3- desired motion : adduction 4- eccentric contraction of gluteus medius , maximus and TFL #Biomechanics-of-gait  Mid stance & Terminal stance The GRFV lies medial to hip joint creating adduction moment that is counterbalanced by hip abductors contraction. The desired motion is hip abduction and the contraction is concentric of hip abductor. At these sub-phases pelvis elevates 1- GRFV pass medial 2- create adduction moment 3- desired motion : neutral 4- concentric contraction of gluteus medius preswing 1- GRFV pass lateral 2- create abduction moment 3- desired movement : abduction 4- eccentric contraction of adductor Magnus & longus #Biomechanics-of-gait  Knee joint Knee at stance phase experiences an adduction torque especially during loading response, midstance, and terminal stance. This is counterbalanced by activity of biceps femoris and gluteus maximus tension on iliotibial band that stabilize the knee. Tension of the ligaments at the knee in frontal plane plays an important role during gait. Subtalar joint The GRFV passes at the lateral border of foot during loading response, so subtalar eversion continues during first part of stance phase. This permit foot to adapt to the supporting surface. The eversion moment is counterbalanced by invertor muscles mainly tibialis anterior, tibialis posterior, FHL, and soleus #Biomechanics-of-gait Thank You #Biomechanics-of-gait Pathological Gait 1-Gluteus Medius Weakness ( Trendelenburg gait ) Gluteus medius weakness may occur as either a frank injury to the gluteus medius or secondarily following an injury to another aspect of the limb. GRFV passes medially to hip joint and creates a strong adduction moment around hip joint so, there is tendency of pelvis and trunk to drop laterally to the opposite side toward non-stance limb this action should be compensated by abductors muscles activity. if the gluteus medius has insufficient strength to hold the pelvis level , the opposite hip and pelvis drops during this phase (LR, MST) if the left gluteus medius is weak, when the individual is in midstance on the left, the right hip and pelvis drops. This is a Trendelenburg gait. #Biomechanics-of-gait  Compensation: an individual may compensate for a gluteus medius deficiency by lean the trunk laterally towards the ipsilateral side of weakness during midstance. Moving the HAT directly over the limb reduces the moment arm of the gravitational force as it shifts the GRFV toward the affected side. So, the weak gluteus medius. is not required to exert as much force If the GRFV passes via hip joint, no moment will be created. If it passes lateral to the joint, it will create abduction moment which will be compensated by activity in adductor moment. Unilateral weakness cause Trendelenburg gait bilateral weakness cause waddling gait. This type of gait on the long run cause scoliosis, back pain, and fatigue. #Biomechanics-of-gait Gluteus maximus weakness ( lurching gait or jack knifing gait ) During initial contact and loading response the GRFV passes anterior to hip joint and creates flexion moment that should be compensated by extensor muscle action When gluteus maximus muscle is weak, it fails to compensate the flexion moment so there is tendency for excessive hip flexion (jack knifing) and anterior pelvic tilting. Compensation: The patient will try to prevent trunk from falling forward by leaning the trunk backward to shift the GRFV behind the axis of hip joint. This pattern of gait called gluteus maximus gait. If the weakness is bilateral there is a backward lean of the trunk during the entire stride. On the long run this cause sever lumbar lordosis. #Biomechanics-of-gait Hip Joint Abnormalities Three conditions around the hip joint will lead to difficulties in stabilizing the pelvis using the abductors: 1. Congenital dislocation of hip ( CDH ) or developmental dysplasia of hip 2. Coxa vara 3. Slipped femoral epiphysis #Biomechanics-of-gait  In all three, the effective length of the gluteus medius is reduced because the greater trochanter of the femur moves proximally, towards the pelvic brim. Since the muscle is shortened, it is unable to function efficiently and thus contracts with a reduced tension. In CDH and severe cases of slipped femoral epiphysis, a further problem exists in that the normal hip joint is effectively lost, to be replaced by a false hip joint, or pseudarthrosis. This abnormal joint is more laterally placed, giving a reduced lever arm for the abductor muscles. The combination of reduced lever arm and reduced muscle force gives these subjects a powerful incentive to walk with lateral trunk bending. In many cases, particularly in older people with CDH, the false hip joint becomes arthritic and they add a painful hip to their other problems. Pain is frequently also a factor in slipped femoral epiphysis. #Biomechanics-of-gait Unequal leg length When walking with an unequal leg length, the pelvis tips downwards on the side of the shortened limb, as the body weight is transferred to it. This is sometimes described as ‘stepping into a hole’. The pelvic tilt is accompanied by a compensatory lateral bend of the trunk. #Biomechanics-of-gait Functional leg length discrepancy Four gait abnormalities (circumduction, hip hiking, steppage and vaulting) are closely related, in that they are designed to overcome the same problem – a functional discrepancy in leg length. An anatomical leg length discrepancy occurs when the legs are actually different lengths, as measured with a tape measure or, more accurately, by long-leg x-rays. A functional leg length discrepancy means that the legs are not necessarily different lengths (although they may be) but that one or both are unable to adjust to the appropriate length for a particular phase of the gait cycle. For natural walking to occur, the stance phase leg needs to be longer than the swing phase leg. If it is not, the swinging leg collides with the ground and is unable to pass the stance leg. The way that a leg is functionally lengthened (for the stance phase) is to extend at the hip and knee and to plantarflexion at the ankle. Conversely, the way in which a leg is functionally shortened (for the swing phase) is to flex at the hip and knee and to dorsiflexion at the ankle. Failure to achieve all the necessary flexions and extensions is likely to lead to a functional leg discrepancy Spasticity of any of the extensors or weakness of any of the flexors tends to make a leg too long in the swing phase spasticity of the flexors, weakness of the extensors or a flexion contracture in a joint makes the limb too short for the stance phase. #Biomechanics-of-gait #Biomechanics-of-gait 1- circumduction Appear in patient with hemiplegia An increase in functional leg length is particularly common following a ‘stroke’, where a foot drop (due to anterior tibial weakness or paralysis) may be accompanied by an increase in tone in the hip and knee extensor muscles ( spasticity of extensors muscle ) Ground contact by the swinging leg can be avoided by circumduction movement The swing phase of the other leg will usually be normal. The movement of circumduction is best seen from in front or behind. Affected muscle 1- weakness of hip flexors (iliopsoas) 2- spasticity of gluteus maximus ❖ Circumduction may also be used to advance the swing leg in presence weak in hip flexors by improving ability of adductor muscles to act as hip flexors #Biomechanics-of-gait 2- Hip hiking Hip hiking is a gait modification in which the pelvis is lifted on the side of the swinging leg, by contraction of the spinal muscles and the lateral abdominal wall. The movement is best seen from behind or in front. hip hiking is commonly used in slow walking with weak hamstrings Affected muscles 1. Weakness in hamstring muscle 2. Spasticity in quadriceps muscle #Biomechanics-of-gait 3- Steppage Steppage is a very simple swing phase modification consisting of exaggerated knee and hip flexion, to lift the foot higher than usual for increased ground clearance. It is best observed from the side. It is particularly used to compensate for a plantarflexed ankle, commonly known as foot drop Affected muscle 1. Weakness in dorsiflexors muscles 2. Spasticity in planter flexors muscle #Biomechanics-of-gait 4-Vaulting The ground clearance for the swinging leg will be increased if the subject goes up on the toes of the stance phase leg This causes an exaggerated vertical movement of the trunk It may be observed from either the side or the front. Vaulting is a stance phase modification, whereas the related gait abnormalities (circumduction, hip hiking and steppage) are swing phase modifications. vaulting may be a more appropriate solution for problems involving the swing phase leg. Like hip hiking, it is commonly used in slow walking with hamstring weakness, when the knee tends to extend too early in the swing phase. It may also be used on the ‘normal’ side of an above-knee amputee whose prosthetic knee fails to flex adequately in the swing phase. Affected muscle 1- weakness of dorsiflexion 2- spasticity of planterflexors muscles #Biomechanics-of-gait Abnormal hip rotation Because the hip is able to make large rotations in the transverse plane, for which the knee and ankle cannot compensate, an abnormal rotation at the hip involves the whole leg, with the foot showing an abnormal ‘toe in’ or ‘toe out’ alignment. is best observed from behind or in front. Abnormal hip rotation may result from one of three causes: 1. A problem with the muscles producing hip rotation 2. A fault in the way the foot makes contact with the ground 3. As a compensatory movement to overcome some other problem. Problems with the muscles producing hip rotation usually involve spasticity or weakness of the muscles which rotate the femur about the hip joint. For example, Imbalance between the medial and lateral hamstrings is a common cause of rotation #Biomechanics-of-gait  weakness of biceps femoris or spasticity of the medial hamstrings will cause internal rotation of the leg. spasticity of biceps femoris or weakness of the medial hamstrings will result in an external rotation. Several foot disorders will produce an abnormal rotation at the hip. Inversion of the foot, whether due to a fixed inversion (pes varus) or to weakness of the peroneal muscles, will internally rotate the whole limb when weight is taken on it. #Biomechanics-of-gait Quadriceps muscle weakness Normally, during early stance as weight is being shifted onto the stance leg (loading response), the line of force falls behind the knee requiring quad contraction to prevent buckling of knee. Quadriceps weakness lead to : 1. Inability to counteract flexion moment 2. Instability in heal strike 3. Decrease shock absorption 4. high tendency for excessive knee flexion Compensation: 1. the main compensation is the action of hip extensors and ankle planter flexors to pull the femur and tibia posteriorly which results in knee extension. 2. Patient lean trunk forward to shift GRFV anterior to knee. #Biomechanics-of-gait  if both quadriceps and the gluteus maximus are paralyzed, a patient may compensate by pushing femur posteriorly with his hand at the initial contact and loading response. The arm support trunk and prevent hip flexion and thrusts knee into extension. After long run of compensation, it leads to fatigue and degeneration of ligaments that support knee. #Biomechanics-of-gait Inadequate dorsiflexion control The dorsiflexors are active at two different times during the gait cycle, so inadequate dorsiflexion control may give rise to two different gait abnormalities. During loading response : dorsiflexors muscle resist movement of planterflexors to permiting foot lowered to the ground gently , if they are weak lead to foot slap During swing phase : dorsiflexors muscle raise foot and achieve ground clearance , if they are weak lead to toe drag during Isw Compensated by Steppage gait Inadequate dorsiflexion control may result from 1. weakness or paralysis of the anterior tibial muscles 2. spasticity of the triceps surae. #Biomechanics-of-gait Abnormal foot contact 1.Talipes calcaneus 2.Talipes equinus 3.Excessive medial contact 4.Excessive lateral contact 5.Talipes equinovarus #Biomechanics-of-gait 1- Talepus calcaneus ( pes calcaneus ) Loading of the heel occurs in the deformity known as talipes calcaneus (also known as pes calcaneus), where the forefoot is pulled up into extreme dorsiflexion Absence of LR – MST – TST – PSW Causes : result of muscle imbalance : spasticity of the anterior tibial muscles or weakness of the triceps surae. the stance phase duration is reduced. The reduced stance phase duration on the affected side reduces the swing phase duration on the opposite side, which in turn reduces the overall stride length. #Biomechanics-of-gait 2- Talepus equinus ( pes equinus ) In the deformity known as talipes equinus , the forefoot is fixed in plantarflexion, usually through spasticity of the plantarflexors. In a mild equinus deformity, the foot may be placed onto the ground flat; in more severe cases the heel never contacts the ground at all and initial contact is made by the metatarsal heads, in a gait pattern known as primary toestrike. 3- Excessive medial contact occurs in a number of foot deformities 1. Weakness invertors muscle or spasticity evertors 2. Pes valgus : medial arch of foot lowered 3. Valgus deformity of knee ( lock knee ) ( genu valgum ) : accompanied by increase walking base #Biomechanics-of-gait #Biomechanics-of-gait 4- Excessive lateral foot contact occurs in a number of foot deformities 1. Spasticity invertors or weakness evertors 2. Genu varum 3. Talipes equinovarus ( club foot ) 5- talipes equinovarus combines equinus with varus, producing a curved foot where all the load is borne by the outer border of the forefoot #Biomechanics-of-gait Insufficient push off In normal walking, weight is borne on the forefoot during the ‘push off ’ in pre-swing. In the gait pattern known as insufficient push off, the weight is taken primarily on the heel and there is no push off phase, the whole foot being lifted off the ground at once. It is best observed from the side. Causes 1. Rupture in Achilles tendon 2. Weakness in triceps surae 3. Pain in forefoot this occur in metatarsalgia 4. Weakness in intrinsic muscle of foot 5. In condition of talipes calcaneus #Biomechanics-of-gait Abnormal walking base The walking base is usually in the range 50‒130 cm. In pathological gait it may be either increased or decreased beyond this range. changes in the walking base may be estimated by eye, preferably from behind the subject. An increased walking base may be caused by any deformity, such as an abducted hip or valgus knee, which causes the feet to be placed on the ground wider apart than usual. A consequence of an increased walking base is that increased lateral movement of the trunk is required to maintain balance. The other important cause of an increased walking base is instability and a fear of falling, the feet being placed wide apart to increase the area of support. This gait abnormality is likely to be present when there is a deficiency in the sensation or proprioception of the legs, so that the subject is not quite sure where the feet are, relative to the trunk. It is also used in cerebellar ataxia, to increase the level of security in an uncoordinated gait pattern. Another effective way to improve stability is to walk with one or two canes. A narrow walking base usually results from an adduction deformity at the hip or a varus deformity at the knee. Hip adduction may cause the swing phase leg to cross the midline, in a gait pattern known as scissoring, which is commonly seen in cerebral palsy. In milder cases, the swing phase leg is able to pass the stance phase leg, but then moves across in front of it. #Biomechanics-of-gait #Biomechanics-of-gait Other gait abnormalities 1. Abnormal movements, for example intention tremors and athetoid movements 2. Abnormal attitude or movements of the upper limb, including a failure to swing the arms 3. Abnormal attitude or movements of the head and neck 4. Rapid fatigue #Biomechanics-of-gait Motion analysis system Final lecture #Biomechanics-of-gait #Biomechanics-of-gait #Biomechanics-of-gait #Biomechanics-of-gait  The main goal of the human movement analysis is the acquisition of quantitative information about the mechanics of the musculoskeletal system while executing a motor task. In general, motion capture (also known as ‘mocap’) is classified into two: 1- marker-based techniques 2- marker-less techniques. 1-Marker-Based Motion Capture The two-basic marker-based techniques are: Active markers (light- emitting diodes or optoelectrical) Passive markers. The objectives of marker system are to accurately represent the motion of limb segments and to define the centers of joint rotation for joint force calculations. #Biomechanics-of-gait #Biomechanics-of-gait a- Active marker system: This system used active marker to determine the anatomical sites. Each marker is a LED that is pulsed sequentially and activated from a power source. So, the system automatically knows the position of each marker. In this system the basic technique consists of placing markers on the skin surface in locations that accurately represent the actions of the underlying joints. These markers are recorded by cameras and their locations translated into motion by complex computer programs. #Biomechanics-of-gait Advantages of active marker system each marker is activated in an automatically known sequence, so the computer know which site is being recorded. Great number of markers can be used close together. Recording rate is much faster Disadvantages of active marker system Dependency on power supply and transmitting cables is restrictive For long duration test, heat generated by LED’s might be problem #Biomechanics-of-gait b- Passive marker system Marker-based analysis is generally performed by mounting retro-reflective markers on the subjects’ bodies and reconstructing their 3-D position via video based optoelectronic systems. If the marker is visible from at least two calibrated cameras at the same time, the 3-D position of a marker can be reconstructed. Marker location is automatically identified by the system through determination of the center of bright area recorded for each marker. #Biomechanics-of-gait System setup The marker location must assure a minimum distance between markers with interval usually is 5-7cm. Two cameras are needed to record the position of each marker in order to determine the 3 D coordinates of each marker. Rigid fixation of camera is needed. One camera usually gives 2D coordinate and 2 cameras give 3D. For gait analysis 3 to 5 cameras are suitable to capture all markers Camera height should be 2-3 m above the floor. Marker position should be picked up each time by at least 2 cameras. The angle between 2 cameras is preferred to be greater than 45º. Windows should be closed to eliminate outside light from test area. Avoid camera light from flashing directly into camera across the room. Passive marker placement applied over the skin directly using double- sided adhesive tapes or can be applied through a wand system. In wand system the marker is strapped to the center of the limb segment to reduce the effect of skin motion #Biomechanics-of-gait Advantages of passive marker system 1. No need for electrical cables 2. Camera works with high speed as it produces large number of frames per second Disadvantages of passive marker system Marker dropout: any event that hides the markers from the video will change the recording. Hand swing over the hip, excessive rotation and overlap of the marker locations within the camera fields can cause marker dropout. #Biomechanics-of-gait Anatomical Landmarks Anatomical landmarks are either bony prominences or bone points of geometrical relevance, which are normally identified by palpation. they can also be identified by imaging, or functional movements. The estimation of 3-D points of objects from two or more images is called ‘stereophotogrammetry’ ❑ There are three major sources of errors in human movement analysis performed with stereophotogrammetry: 1- Instrumental errors: these errors stem from the results of both instrumental noise and volume calibration inaccuracies. 2- Soft tissue artefacts 3- Anatomical landmark misplacement #Biomechanics-of-gait Skin marker setup In bilateral analysis during gait, 20 markers are applied over the skin on specific sites which are: Acromion (2 markers; left and right) 12th thoracic vertebra Sacrum Anterior superior iliac spine (2 markers; left and right) Greater trochanter (2 markers; left and right) Superior border of patella (2 markers; left and right) Tibial tuberosity (2 markers; left and right) Knee joint line (2 markers; left and right) Lateral malleolus (2 markers; left and right) Heel (2 markers; left and right) Between 2nd and 3rd metatarsal bone (2 markers; left and right) In unilateral analysis: 7 markers are applied over skin 3 markers over foot 3 markers over knee 1 marker over greater trochanter. #Biomechanics-of-gait Marker-less system Marker-less motion capture ensures an important reduction of the amount of time for setup preparation in comparison to marker based techniques. Besides, inter-operator variability is eliminated since no specialized operator is needed to place markers on the skin. #Biomechanics-of-gait #Biomechanics-of-gait