Purpose: The purpose of this study was to determine, first, if there is measurable deficit in proprioception in an anterior cruciate ligament (ACL)-deficient knee, either compared to the contralateral knee or external controls; second, if this deficit, if present, improves after ACL reconstruction; and third, if improvement occurs, what the time course of improvement is.
Type of study: Prospective cohort study.
Methods: Patients undergoing ACL reconstruction at the University of Chicago, demonstrating a full and painless range of motion and no other knee ligament injury or history of previous knee surgery, were eligible. Twenty-six patients, with an average age of 25 years (range, 16 to 48) were enrolled. Average time from injury to reconstruction was 8 weeks. The patients' contralateral knee served as an internal control, and 26 age-matched and gender-matched healthy volunteers were enrolled as an external control group. ACL reconstructions were performed using a single-incision technique with either bone-patellar tendon-bone or quadrupled hamstring autograft. They were allowed immediate weightbearing as tolerated and participated in a standardized rehabilitation program, with the goal of returning to sport at approximately 6 months. Proprioception testing was carried out using an electrogoniometer, in a seated position. Joint position sense (JPS) and threshold to detection of passive motion (TDPM) were measured preoperatively and at 3 and 6 weeks and 3 and 6 months postoperatively.
Results: Mean KT-2000 values 6 months postoperatively were 1.38 mm (+/-2). Modified Lysholm score improved significantly (P <.01). Calculated r values were 0.65 for JPS and 0.96 for TDPM. No significant differences in postoperative proprioception were found between hamstring and patellar tendon grafts or among patients with meniscus injury, meniscus repair, or chondral injury. Preoperatively, the mean TDPM in both the injured and contralateral knees was significantly higher (worse) than in the external control knees (P =.008; P =.016). Evaluation of changes in proprioception from preoperative to 6 months postoperative showed significant improvement in both injured and contralateral knees (P =.04; P =.01). At 6-month follow-up, there was no significant difference from controls.
Conclusions: TDPM was a more reliable method than JPS for testing proprioception before and after ACL reconstruction in this study. Bilateral deficits in knee joint proprioception (TDPM) were documented after unilateral ACL injury. Reconstruction of a mechanical restraint (ACL graft) was believed to have a significantly positive impact on early and progressive improvement in proprioception.