The purpose of this study is to correlate the measurement of anterior knee laxity using the Rolimeter with the functional outcome of anterior cruciate ligament (ACL) deficient knees. We tested 29 patients (12 males/17 females) with an average age of 33 years (range 19-47) that had been treated for ACL rupture, either by reconstruction or conservatively. The average follow-up at time of testing was 33 months (range 6-67).Functional outcome was graded by means of a questionnaire based on the IKDC score, the sports activity rating scale (SARS), the Cincinnati knee-rating system and the activities of daily living (ADL) scale, and by two functional knee tests (the one-leg hop test and the cross-over hop test). The anterior knee laxity was measured for both knees with the Rolimeter, and the side-to-side difference was calculated. We have found no correlation between the joint laxity and the functional outcome score.(P>0.05). When we compared both groups, we found a significant, though very low, correlation between the laxity and the functional questionnaire for the reconstructed group. (r=0.51, P=0.036). Therefore, the joint laxity measurement does not necessarily reflect the functional outcome of ACL-deficient knees. An explanation can be found in the importance of the proprioception and neuromuscular control in compensating the ACL-deficient knee.