Joint position sense is not changed after acute disruption of the anterior cruciate ligament.

We evaluated the impact of acute, isolated ACL disruption on knee joint proprioception by means of passive-active and active-active joint position sense (JPS) measurement techniques. 18 subjects with acute, isolated and unilateral ACL disruption were tested for JPS in a standing position. The test protocol included 6 trials for each leg. In each trial, the lower leg was passively positioned to an index angle approximating either 30 degrees or 70 degrees, followed by 5 active repetitions of the index angle where the subjects attempted to reproduce the index angle to the best of their ability. The errors from the exact index angle reproduction were calculated as both real (showing both magnitude and direction) and absolute values (only magnitude). All subjects had a tendency to reproduce the index angle with both the injured and normal knees in a more flexed position (overestimation). Only the absolute error produced by the active-active test at flexion angles greater than 45 degrees produced a significant difference with a larger error for the normal knee. In all other comparisons between the injured and the normal knee no differences were found. We conclude that the afferent signals which are compromised by an acute tear of the ACL are insignificant compared to afferent signals from the other joint and muscle receptors.