Anterior cruciate ligament function: evaluation with motion analysis system

A new non-invasive quantitative method for evaluation of the anterior cruciate ligament function was tested in 24 asymptomatic subjects and in 37 patients with arthroscopically proven unilateral rupture of the anterior cruciate ligament using a 3D optical motion analysis system. In the normal group, the average difference (d) in the anterior displacement of the tibia between the left and the right side under a displacement force of 250 N was 0.56 mm (range 0.1 mm to 1.9 mm), while in the patients the parameter d in the anterior displacement of the tibia between the injured and uninjured side under a displacement force of 250 N was 3.98 mm (range 0.6 mm to 7.9 mm). If the maximum value of the parameter d in normal subjects was used to discriminate between groups then 8% of the patients were classified as normal. On the other hand, if the minimum value of the parameter d in patients (0.6 mm) was used to discriminate between groups, 17% of the normal subjects were classified as abnormal.