Kinetic Analysis of Gait PDF

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: inertia, gravity, and ground reaction force (GRF). Internal forces: are primarily by muscles. The ligaments, tendons, joint capsules, and bony...

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: inertia, gravity, and ground reaction force (GRF). Internal forces: are primarily by muscles. The ligaments, tendons, joint capsules, and bony components assist the muscle by resisting, transmitting and absorbing forces. A- 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 a distance away from the joint axis, a gravitational torque is created. This torque will cause the 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. 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 Dr Noha Elserty Sagittal plane The relationship of the GRFV to the joint axis used to express the type of moment (flexion, extension) that is acting around joints. The GRFV location in relation to joint axis (anterior, posterior) and the resulting moments represented in the following table Initial contact Loading Mid stance Terminal Preswing response stance Hip A/ flexion A/ flexion P/ P/ P/ extension extension extension Knee A/ extension P/ flexion A/ A/ P/ flexion extension extension Ankle P/ P/ A/ A/ A/ planterflexion planterflexion dorsiflexion dorsiflexion dorsiflexion Frontal plane: The relationship of the GRFV to the joint axis of hip, knee, and subtalar joints in frontal plane may lie lateral or medial or neutral and that determines the type of moment either adduction or abduction (or eversion and inversion). This relation is summarized in the following table. Initial Loading Mid stance Terminal Preswing contact response stance Hip L/ abduction M/adduction M/adduction M/adduction L/ abduction Dr Noha Elserty  Knee L/ abduction M/adduction M/adduction M/adduction Neutral Subtalar Neutral L/ Eversion L/ Eversion M/ Inversion Neutral b- 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. Principle: 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 Dr Noha Elserty Summary of Muscular Activation Patterns through the Gait Cycle Muscles perform several functions during gait. Muscles may act as stabilizers, accelerators, or decelerators. When muscles provide stabilization, they often work isometrically to position one joint or segment while another joint or segment moves. If muscles work as accelerators, they usually contract concentrically to move a segment forward. If they work as decelerators, they are eccentrically contracting to slow a movement or absorb forces produced by a motion. Throughout the stance phase, muscles work to provide weight acceptance, limb stabilization, energy absorption, and propulsion of the limb into swing phase. Sagittal plane analysis Dr Noha Elserty Hip joint: -Initial contact: The GRFV passes anterior to the hip joint creating a flexion moment that is counterbalanced by eccentric contraction of gluteus maximus and hamstring. -Loading response: As the limb starts to move from flexion into extension the contraction of the gluteus maximus changes into concentric contraction. The activity of the gluteus maximus increases while the activity of the hamstring decreases. -Mid stance, terminal stance and preswing: As the GRFV passes posterior to the hip joint, it creates an extension moment that is counterbalanced by flexors (mainly iliopsoas, tensor fascia lata, and rectus femoris) activity. The contraction is eccentric at midstance and terminal stance while it changed into concentric at preswing to initiate the swing phase. -Initial swing: Hip flexors mainly iliopsoas, sartoruis, and gracilis contract concentrically to initiate swing phase. The sartoruis, and gracilis display small levels of activity at the knee joint to induce knee flexion. -Midswing: Muscle action may be absent or minimal in flexors. -Terminal swing: flexors activity stopped and the hamstring and gluteus maximus contract eccentrically to control the forward progression of the lower limb. Dr Noha Elserty