PAPER 099: THE EFFECTS OF CONCENTRIC QUADRICEPS FATIGUE ON KNEE ANGLES AND KNEE MOMENTS DURING GAIT IN YOUNG, SEDENTARY FEMALES

Abstract

Purpose: Adults with knee osteoarthritis (OA) show biomechanical changes in gait which may be linked to the quadriceps weakness often associated with knee OA. The purpose of this study was to mimic the effect of quadriceps weakness by inducing fatigue to determine if this produced gait characteristics similar to those present in knee OA.

Method: Sixteen healthy, sedentary female subjects between the ages of 19 and 35 years participated. Subjects were randomly assigned to perform a quadriceps-fatiguing protocol using a CybexTM isokinetic dynamometer (n=9) or a resting control group (n=7). Gait was evaluated before and after the rest or the fatiguing protocol. Infrared and virtual markers were used to record the locations of 16 anatomical landmarks. Marker position was recorded using an Optotrak motion capture system. An AMTI force plate collected ground reaction forces. Joint kinematics and kinetics were calculated using standard techniques. Maximum, minimum and time to peak were calculated for knee flexion angle, and the flexion, adduction and rotation moments during stance. A 2-factor (group, pre-post) mixed model ANOVA was used to test main effects and interactions (alpha = 0.05). Post hoc Bonferroni testing (alphaadj=0.0125) was used to determine pair wise differences.

Results: The two groups were statistically similar at baseline (p> 0.05) in terms of their age, mass, height, strength, and self-selected walking velocity. The fatigue protocol resulted in a 49 ± 12% decrease in peak knee extensor torque. The statistical results showed that knee flexion and external rotation moments decreased, the time to peak knee flexion angle increased, and the minimum knee adduction moment increased from pre-test to post-test in the fatigued group (p< 0.05).

Conclusion: Induced quadriceps fatigue alters kinematic and kinetic gait parameters. The changes are consistent with the gait characteristics observed in patients with knee OA and imply a change in joint motion and loading. These results provide preliminary evidence of a direct link between quadriceps weakness and the mechanical environment of the knee joint. This may be useful in developing more specific management programs for knee OA.