Sagittal Plane Kinematics PDF

Sagittal Plane kinematics In the sagittal plane, the two vertical oscillations of the body’s COM follow a smooth sinusoidal curve. The curve’s highest point occurs at midstance for each foot while the lowest segment of the sinusoidal curve is at double support. PELVIS The pelvis must multifunction...

Sagittal Plane kinematics In the sagittal plane, the two vertical oscillations of the body’s COM follow a smooth sinusoidal curve. The curve’s highest point occurs at midstance for each foot while the lowest segment of the sinusoidal curve is at double support. PELVIS The pelvis must multifunction 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. Additionally, 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. 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. Hip joint The hip joint moves through 40° of sagittal motion in a single gait cycle. At initial contact, the hip is flexed at 25° to 30°.As the stance phase continues, the hip progressively moves into extension, reaching its maximum extension at 10° of hyperextension by terminal stance. From initial contact to midstance, the trunk moves forward over the foot and continues its forward movement to advance in front of the foot immediately after midstance. Hip hyperextension at terminal stance is accompanied by extension of the lumbar vertebrae and an anterior pelvic tilt. Once the hip reaches maximum extension at terminal stance, the hip begins movement towards flexion during preswing as it prepares to lift the limb off the ground; by the end of stance, the hip is near neutral, and as the limb begins into the swing phase, the hip continues a steady increase into flexion until midswing when the hip is slightly more than 30° of flexion. After midswing, its flexion decreases slightly and is maintained until terminal swing when it starts to move towards extension in preparation for initial contact. 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. 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 Summary of hip joint: Hip Stance phase Swing phase joint IC LR MSt TSt * PSw Isw MSw * TSw 30º 25º 0º 10º 0º 20º 30º 30º flexion Flexion hyperextension flexion flexion flexion TSt: hyperextension arc, MSw: flexion arc Note: hip extension arc acts to transfer weight to contralateral limb, while hip flexion arc acts to clear foot from the ground. 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 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 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. Summary Knee Stance phase Swing phase joint IC LR * MSt TSt PSw Isw MSw * TSw * * 5º 15-20º 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 2 nd 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, 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 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 LR: 1st planterflexion arc, TSt: 1ST dorsiflexion arc, PSw: 2nd planterflexion arc, MSw: 2nd dorsiflexion arc Note: 1st planterflexion arc acts as shock absorption, 2nd planterflexion arc act for propulsion. 1st dorsiflexion arc act for transfer weight to the contralateral limb, 2nd dorsiflexion arc act to clear foot form ground and preparation for new step.