The association between external-ground-reaction force and knee-joint kinetics during partial- and full-weight-bearing gait
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Background Progressive weight-bearing is recommended following autologous chondrocyte implantation. This weight-bearing program assumes that increasing external loads experienced at the foot during gait are closely related to external-knee-joint moments. We investigated this relationship, and examined other variables that may contribute to knee-joint kinetics of which the clinician can modify using practical instruction within a clinical setting. Methods Gait analysis was performed in 51 patients following autologous chondrocyte implantation, during various partial- and full-weight-bearing conditions. The contribution of ground-reaction force, kinematic and spatio-temporal gait parameters to external-knee moments was investigated within weight-bearing levels less than 60%, between 60% and 90% and more than 90% of individual body weight. Findings There was no association between peak-ground-reaction force and the knee-adduction moment within the 60-90% and more than 90% weight-bearing conditions, nor the peak-knee-flexion moment at less than 60% weight-bearing. Peak-ground-reaction force accounted for no more than 21.4% and 18.6% of the variance in the knee-adduction and flexion moments, respectively, within any weight-bearing condition, while the combination of peak-ground-reaction force, kinematic and spatio-temporal parameters investigated accounted for no more than 39.7% and 52.2%, respectively. Foot-progression angle and knee-flexion during weight acceptance accounted for a significant (P < 0.05) portion of the variance in external-knee moments, particularly at higher levels of weight-bearing. Interpretation A large amount of variance in knee moments may be attributed to variables other than external loads, some of which can be modified by the clinician. Clinically, this is important for any therapist implementing progressive weight-bearing protocols.