Relationships between the swing-phase knee flexion angle and pre-swing-phase knee muscle activity during gait soon after total knee arthroplasty

Abstract

[Purpose] To examine the relationships between the knee flexion angle during the swing period and knee muscle activity during the pre-swing period after total knee arthroplasty (TKA). [Participants and Methods] A total of 24 knees treated with TKA were examined. The knee angle during gait was measured using gait images video-recorded from the sidelines. Electromyography was performed involving the rectus femoris, vastus lateralis, and biceps femoris of the operated leg. The gait assessment was conducted at 4 weeks after surgery. The relationships among the angles of the knee at toe off/when maximally flexed and relative/co-activation index values of each muscle during each phase of gait were analyzed. [Results] The maximum knee flexion angle during the swing period was moderately correlated with the relative muscle activity index value of the rectus femoris and co-activation index value of the vastus lateralis and biceps femoris during the pre-swing period. [Conclusion] The overactivity of the rectus femoris and excessive co-activation of the vastus lateralis and biceps femoris during the pre-swing period may lead to stiff-knee gait.