Purpose of Study To investigate the proprioceptive function of patients with an ACL rupture before and after reconstruction and correlate these findings with ligament laxity testing and clinical outcome measures.

Summary of Methods and Results Fifty patients with an ACL rupture and 50 normal controls were recruited to the study. The Biodex Balance SD System was used to assess knee proprioception. This equipment measures proprioceptive function using an electronic platform. The balance of the subject is computed using stabilometry and an Overall Stability Index (OSI) is produced. A lower score reflects better proprioception. Knee stability was assessed clinically and with the Rolimeter knee arthrometer in all subjects. Participants were evaluated using the Tegner, Lysholm, Cincinnati and IKDC scoring systems. In the ACL group, 34 patients underwent ACL reconstruction and returned for their follow-up review 3 months post-operatively. The proprioceptive function of the injured knee of the ACL group (mean OSI 0.70) was significantly poorer compared to that of their uninjured knee (mean OSI 0.46, p<0.001, 95%CI 0.14, 0.34) and to the Normal Control group (mean OSI 0.49, p=0.01, 95%CI 0.05, 0.38). There was a significant improvement in proprioception of the injured knee following ACL reconstruction (mean OSI 0.47, p=0.003, 95%CI 0.10, 0.42). A significant correlation was found between pre-operative proprioception measurements and all the pre-operative knee outcome scores, however this correlation was not found post-operatively. No correlation was found between ligament laxity testing and either proprioception measurements or knee outcome scores.

Conclusion Patients with ACL ruptures were found to have a proprioceptive deficit which improved following reconstruction, the measurements of which correlated better with clinical outcome scores than instrumented ligament laxity testing.