Abstract
Rupture of the anterior cruciate ligament (ACL) of the knee results in loss of static and dynamic stability. Compensation, the ability to return to full previous physical activity including cutting and pivoting maneuvers, is variable in those who have sustained this injury. The purpose of this study was to examine the mechanisms enabling compensation in subjects with ACL deficiency (ACL-D). Subjects and methods. Seventeen subjects with ACL-D were grouped by functional status (i.e. copers, noncopers and adapters) based on the Knee Outcome Survey, subjective report and strength measures. Muscle responses during dynamic balance testing (DBT) and treadmill walking were then compared between groups and to a comparative group, consisting of seven subjects without ACL-D. Relative latencies and relative amplitudes were calculated. Somatosensory evoked potentials (SEPs) identifying loss/maintenance of P27 potential and 3) proprioception testing using threshold to detection of passive movement (TDPM) were measured. Results. Copers had a proprioceptive deficit, altered SEPs and altered postural synergies. Adapters demonstrated normal strength, proprioception, SEPs and altered postural synergies. Non-copers had deficits in strength and proprioception, but not altered SEPs or postural synergies. While both copers and adaptors had altered synergies, copers demonstrated faster and increased hamstring activation. Conclusions. The alteration of synergy and SEPs in copers suggest changes in central pre-programming for the purpose of maintaining joint stability.