Lecture 3 analysis of gait (2).pdf

Ass. Prof. Dr. Noha Elserty Analysis of gait Sagittal Plane kinematics Knee joint The knee joint moves through two cycles of flexion and extension during the gait cycle. At initial contact, the knee is near full extension (about 3° to...

Ass. Prof. Dr. Noha Elserty Analysis of gait Sagittal Plane kinematics Knee joint The knee joint moves through two cycles of flexion and extension during the gait cycle. At initial contact, the knee is near full extension (about 3° to 5° of flexion). Immediately following initial contact, the knee flexes during loading response. This flexion movement provides shock absorption of compression forces that occur when the body weight impacts the ground, and it also assists in weight transfer as the body begins to move toward a single-leg support stance. By the end of the loading response phase, the knee is flexed 15° to 20°. The knee then moves towards extension during midstance; this motion minimizes the muscular effort required during single-limb weight-bearing. Maximum extension at the knee occurs during terminal stance. Immediately after achieving full extension, the knee starts to flex to achieve its maximal stance-phase flexion at 35° to 40° by preswing. During initial and midswing, the knee flexes to shorten the limb and clear the foot from the floor. Maximum knee flexion of the entire gait cycle occurs during midswing, with the knee at 60° to 65° of flexion. During the terminal swing, the knee extends to nearly full extension, so it is able to assist the other limb joints in achieving an adequate step length, advancing the limb, and preparing for initial contact once again. 1 Ass. Prof. Dr. Noha Elserty Summary Knee Stance phase Swing phase joint IC LR * MSt TSt PSw Isw MSw * TSw * * 5º 15-20º 0 or 5º 0º 35-40º 40-60º 60-65º 0º flexion Flexion flexion flexion flexion flexion LR: the 1st arc of knee flexion, TSt: the 1st arc of knee extension, MSw: the 2nd arc of knee flexion, TSw: the 2nd arc of knee extension Note: first knee flexion arc acts as a shock absorption, while 2nd knee flexion arc acts to clear foot from the ground First knee extension arc acts to transfer weight to contralateral limb, while 2nd knee extension arc acts for preparation for new step. Ankle joint and foot The ankle plantarflexes and dorsiflexes twice during the gait cycle. At the moment of initial contact, the ankle joint is in sagittal plane neutral. During loading response, 2 Ass. Prof. Dr. Noha Elserty the ankle rapidly plantarflexes (15º planterflexion) so the entire plantar foot surface contacts the floor. After loading response, the tibia advances forward over the fixed foot into midstance, so by the end of midstance the ankle is in about 5-10° of dorsiflexion. At terminal stance 10º of ankle dorsiflexion is the close-packed position of the ankle and provides maximal talocrural joint congruency. As the heel rises off the floor during terminal stance, a second wave of plantarflexion occurs, peaking at about 20°-30º by preswing. This plantarflexion motion propels the limb into swing phase then planter flexion starts to decrease till 10º at initial swing. The foot dorsiflexes to neutral or slight dorsiflexion to clear the toes from the floor and maintains this position throughout the midswing and terminal swing. An essential but often overlooked sagittal plane motion occurs in the metatarsophalangeal joints (MTP) during the stance phase after midstance to preswing. During loading response, the MTP joints are in a neutral position. The MTP joints hyperextend as the body’s COM moves forward of the weight-bearing 3 Ass. Prof. Dr. Noha Elserty limb and the ankle starts to plantarflex. Extension becomes most apparent during terminal stance until the MTPs reach their maximum motion,55° to 60°, by the end of preswing. During the swing phase, hyperextension of the MTP joints is maintained at about 30° to 40°35 for toe clearance but gradually decreases to 25° by the time of initial contact. Summary Ankle Stance phase Swing phase joint IC LR* MSt TSt* PSw* Isw MSw* TSw 0º 15º 5-10º 10º 20-30º 10º 0º 0º neutral planter dorsiflexion dorsi planter planter Flexion flexion flexion flexion st ST LR: 1 planterflexion arc, TSt: 1 dorsiflexion arc, PSw: 2 planterflexion arc, MSw: 2nd nd dorsiflexion arc Note: 1st planterflexion arc acts as shock absorption, 2nd planterflexion arc acts as propulsion. 1st dorsiflexion arc act to transfer weight to the contralateral limb, 2nd dorsiflexion arc act to clear the foot form the ground and preparation for new step 4 Ass. Prof. Dr. Noha Elserty Frontal Plane kinematics Pelvis The pelvis tilts laterally in the frontal plane about 8° on each side. In unilateral stance, the pelvis of the swing leg tilts laterally downward about 8°. This lateral drop occurs on the swing leg since the stance leg adducts. This small but important motion serves two purposes: 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. Hip joint: Hip motions in the frontal plane directly impact pelvic motion. Frontal plane hip motions offer crucial contributions to stability and efficiency during gait. 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. 5 Ass. Prof. Dr. Noha Elserty 6