Biomechanics Analysis of Gait PDF

# Analysis of Gait ## Freely Chosen Walking Speed - 64 Normal Men - Left Limb: 62% Stance, 38% Swing - Right Limb: 38% Stance, 62% Swing - Gait Cycle Duration: 0 - 1.4 seconds ## Fast Walking Speed - 64 Normal Men - Left Limb: 58% Stance, 42% Swing - Right Limb: 42% Stance, 58% S...

# Analysis of Gait ## Freely Chosen Walking Speed - 64 Normal Men - Left Limb: 62% Stance, 38% Swing - Right Limb: 38% Stance, 62% Swing - Gait Cycle Duration: 0 - 1.4 seconds ## Fast Walking Speed - 64 Normal Men - Left Limb: 58% Stance, 42% Swing - Right Limb: 42% Stance, 58% Swing - Gait Cycle Duration: 0 - 1.4 seconds ## Spotlight on Walking versus Running - The speed of movement does not differentiate walking from running. - Walking is defined by the presence of double-limb support, while running does not. - When walking at a faster pace, the period of double-limb support decreases. - Running is characterized by the absence of double-limb support and the presence of float periods, where both feet are off the ground. ## Kinematics Analysis ### Determinants of Gait - The six determinants of gait are adjustments that the body makes to minimize movement of the body's center of gravity (COG). - Six determinants of gait: 1. Pelvic rotation in the transverse plane. 2. Lateral pelvic tilting in the frontal plane. 3. Knee flexion in stance phase. 4. Knee, ankle and foot interaction. 5. Physiologic valgus of the knee. ### Functions of the 6 Determinants of Gait: 1. Increase the efficiency and smoothness of gait. 2. Decrease the vertical and lateral displacement of the center of gravity to reach 2 inches. 3. Decrease the energy expenditure during normal gait. 4. Make the gait smoother and easier. #### 1. Pelvic Rotation: - The pelvis rotates alternately to the right and left in relation to the line of progression in the transverse plane about the vertical axis. - Associated hip movement: Internal hip rotation occurs in stance phase, and external rotation occurs in the swing phase. - The average magnitude of pelvic rotation is 4 degrees in swing phase and 4 degrees in stance phase, for a total of 8 degrees. - Function of 1st determinant of gait: a. Pelvic rotation results in lengthening of lower extremities. The limb is lengthened by increasing the distance between the points of floor contact and the base of the trunk. The swinging limb is lengthened in terminal swing by forwardly rotating pelvis, and the weight-bearing limb is lengthened in terminal stance by the posterior position of the pelvis. Both stance and swing limbs are lengthened as the COG descends to its lowest level. b. The relative lengthening helps to prevent an excessive drop of the COG, and pelvic rotation functions to minimize the depression of the COG. #### 2. Lateral Pelvic Tilting: - The pelvis tilts downward on the swing leg (opposite the weight-bearing leg) along the frontal plane around the sagittal axis. This causes the COG to reach its highest point in the curve. - Associated hip movement: Pelvic drop produces adduction in the stance hip. Hip abduction occurs in the swing limb. - The average magnitude of pelvic drop is 4-5 degrees. - Function of 2nd determinant of gait: - Prevents excessive rise of COG and helps to minimize elevation of the COG. #### 3. Knee Flexion in Stance Phase: - At initial contact, the knee is almost extended 0 degrees. - At loading response, the knee joint begins the first arc of flexion (15 - 20 degrees). - At preswing, the knee joint flexes up to 35 - 40 degrees to start the second arc of knee flexion. - Function of 3rd determinant of gait: - Shock Absorption - Prevent upward displacement of COG. - Decrease energy expenditure. #### 4. & 5. Knee, Ankle and Foot Interaction: - Movements at the knee occur in conjunction with movements at the ankle and foot. - At stance phase of gait: knee flexion is accompanied by ankle planter flexion as in loading response and preswing, and knee extension is accompanied by ankle dorsiflexion as in initial contact, mid stance, and terminal stance. - Function of 4th and 5th determinants of gait: 1. To prevent a sudden change of vertical displacement of COG from downwards to upwards. 2. This led to shortening of the extremity and thus prevent sudden rise in body's COG after heel strike. #### 6. Physiologic Valgus of the Knee - There is a normal valgus angle between the femur and tibia, which places the knees closer to each other. - The femoral and tibial axes form an angle medially at the knee joint of 185 degrees to 190 degrees. So the femur forms 5 degrees to 10 degrees with the vertical line, creating a normal physiological valgus of the knee. - The physiological valgus at the knee reduces the width of the base of support. - Function of 6th determinant of gait: - Normal physiological knee valgus prevents excessive lateral displacement of COG. ## Kinetic Analysis - Kinetic analysis is a branch of mechanics dealing with the forces that cause motion. - Two forces act on the body: 1. *External forces*: Gravity, inertia, and ground reaction force. 2. *Internal forces:* Created primarily by muscles, ligaments, joint capsules, tendons, and bony components, assisting the muscles by transmitting, resisting, and absorbing forces. ### 1. External Forces: - **a. Gravitational Force**: Acts on the body downward as a result of interaction with the ground. The body weight is represented by a line of gravity. - **b. Ground Reaction Force**: Equal in magnitude and opposite in direction to the force of gravity. Most important force during walking. ### A. Line of Gravity: - An imaginary vertical line that passes perpendicularly through the body, connecting the center of gravity (COG) of the segment above to the COG of the segment below.