Proprioception after an acute knee ligament injury: a longitudinal study on 16 consecutive patients

A defect in proprioception has been found in selected patient groups that have an anterior cruciate ligament deficient knee at different times after the original injury. The time of development and the extent of such defects were studied longitudinally on 16 consecutive patients. During the first year after a primary knee injury, which included a complete rupture of the anterior cruciate ligament, we repeatedly performed three tests of proprioception: (a) one to determine the threshold for detecting a passive motion from starting positions of 20 and 40 degrees, (b) an active reproduction of a passive angular change, and (c) a visual estimation of a passive angular change. The injured limb was compared with the uninjured limb and with the limbs of an age-matched reference group of healthy subjects. The population did not have a normal distribution, and some patients had consistently extreme recordings in the threshold tests at the various times of testing. Significant differences were found between the groups at the starting position of 20 degrees, when the injured knee was compared with the uninjured knee, after 1 month (p = 0.05), and after 2 months (p = 0.03). There was a trend toward a higher threshold for detecting a passive motion when the injured side was compared with the knees of the reference group at 1 month (p = 0.06) but not later on. A similar pattern was found for the injured knee at the starting position of 40 degrees, but it was not significant. An impaired ability to detect a passive motion was registered for the nearly extended knee 1 and 2 months after a primary injury. In the active reproduction and visual estimation tests, no significant defects were found at any time during the first year in these consecutively studied patients.