The purpose of this series of studies was to characterize neuromuscular adaptations to (1) ACL rupture in individuals with varying abilities to compensate for the injury, and (2) surgical reconstruction of the ligament with semitendinosus/gracilis autograft. First, the voluntary muscle control strategies of individuals with complete unilateral ACL rupture who were classified as non-copers were compared to people with uninjured knees using an established target-matching protocol, a dynamic testing protocol, and electromyography. Non-copers displayed diminished muscle control in comparison to the uninjured subjects. The quadriceps muscles were active even during flexion tasks suggesting the injured subjects had significant quadriceps dyskinesia. The altered quadriceps control was observed in static and dynamic tasks, suggesting that the non-copers have global quadriceps dysfunction. Second, non-copers were tested before ACL reconstruction and at the time they returned to full sports activity using magnetic resonance imaging and voluntary muscle control testing. Although the surgical procedure had a significant impact on semitendinosus and gracilis muscle morphology, excellent clinical outcomes were observed. Most subjects displayed evidence of tendon regeneration. Muscle volume was directly related to tendon regeneration. The voluntary muscle control strategies of the semitendinosus and gracilis did not appear to be affected by the surgical procedure. Significant improvement in voluntary muscle control was observed in most muscles after surgery. Finally, the muscle morphology of a small sample of people who compensate well for ACL rupture (copers) was compared to that of non-copers and those with uninjured knees. The non-copers demonstrated significant quadriceps atrophy, whereas the morphology of the copers' muscles was not significantly different from that of the uninjured subjects. In summary, this series of studies provides important insight into the neuromuscular adaptations to complete ACL rupture and reconstruction including the most comprehensive work to date on the effects of ACL reconstruction with hamstrings autograft on neuromuscular function.
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