The relationship between passive joint laxity and functional outcome after anterior cruciate ligament injury

Twenty patients with anterior cruciate ligament-deficient knees were studied. Ten patients returned to all sports activities (compensators) and 10 patients were not improved with nonoperative management and required surgical stabilization (noncompensators). Joint laxity was measured using a KT-2000 arthrometer (manual maximum Lachman). Subjects completed a Lysholm questionnaire and Knee Outcome Score. The International Knee Documentation Committee form was also completed. Patients also rated their knee function on a scale of 1 to 100. There was no difference in level and frequency of athletic activity between the two groups before their anterior cruciate ligament injuries as determined by the knee outcome score. The compensator group had a mean side-to-side difference of 3.25 mm at 89 N and the noncompensators had a mean difference of 3 mm preoperatively. Manual maximum tests gave side-to-side differences of 6.7 mm for the compensators and 6 mm for the noncompensators. There were no differences in laxity measures between groups. The correlation between knee outcome scores and side-to-side laxity measurements were not significant. Measurements of anterior laxity in anterior cruciate ligament-deficient patients were not correlated with measures of functional outcome used in this study. Functional outcome measurements that are partially based on joint laxity measures, such as the International Knee Documentation Committee form, may artificially overestimate the disability after anterior cruciate ligament rupture.