Biomechanical factors influencing knee joint moments during walking.

The ability of the weight bearing knee joint remain hyperextended and support the amputee is characterized by its stability. Stability is very important to the majority of the above knee (A/K) amputees, while there are a multitude of objective and subjective factors influencing knee stability, this study focuses on the contribution to knee stability made by the head, arms and trunk (HAT), contralateral/sound leg and ipsilateral/prosthetic hip. The analysis is based on the experimentally obtained data for two normal and two A/K amputee subjects walking on level ground at their free cadence. The measured gait variable were foot-floor reaction forces and moments, and displacements of the ankle, knee and hip joints. An inverse dynamics approach was applied to determine joint reaction forces and moments. The analysis of the effect of particular body segments on knee joint stability shows that there is no single most dominant body segment effect throughout the stance phase. The contralateral foot floor reaction force is dominant just after heel contact and just before toe off of the ipsilateral leg. The contralateral leg inertial force is dominant at midstance. The foot-floor reaction force initially extends the knee and later flexes the knee joint. The contralateral leg inertial force extends the knee joint at the midstance phase. The HAT is dominant during the rest of the stance phase. At the first half of the stance phase the HAT inertia is the dominant stabilizing factor while the gravity force flexes the knee, and vice versa during the second half. The effect of the ipsilateral thigh moment is virtually negligible throughout the stance phase. The effect of the ipsilateral hip moment varies from subject to subject. In general the ipsilateral hip assists in hyperextending the knee and in the case of the A/K amputees it assists in knee break. The results also indicate that the contralateral leg is dominant for causing the knee to move into hyperextension, whereas both the ipsilateral hip and HAT are responsible for knee break. These results have implications for treatment modalities for restoring normal gait in injured people, training procedure for A/K amputees and design specifications for A/K prosthesis.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/105618/1/9135709.pdfDescription of 9135709.pdf : Restricted to UM users only