The effect of enforced exercise on the healing of ligament injuries

Abstract

Previous studies have documented that mobilization ad libitum has a beneficial effect on the healing of ligaments as compared to immobilization. This study was under taken to determine whether enforced exercise (over and above motion ad libitum) would have a further beneficial effect or, instead, an adverse effect on the healing of ligaments. Large male Sprague-Dawley rats with unrepaired transections of the medial collateral ligament were sep arated into five groups of similar mean weights. Two of these groups had the anterior cruciate ligament and the medial capsule transected in addition to the medial collateral ligament, rendering the knee unstable. The groups were then subjected to varying regimens of enforced exercise (swimming). After 12 days, the me chanical characteristics of the femur, medial collateral ligament, and tibia complex were evaluated. Rats with intact secondary valgus stabilizers (medial capsule and anterior cruciate ligament) that swam daily for either 5 (moderate) or 15 (near exhaustion) minutes were found to have increases in the tensile strength of the femur, medial collateral ligament, tibia complex as compared to rats that did not swim. Unstable knees (with tran sected secondary valgus stabilizers) did not show an increase in the tensile strength of the femur, medial collateral ligament, tibia complex when subjected to moderate increase in enforced exercise (swimming 5 minutes). The unstable groups were, however, signifi cantly more lax than the groups that underwent identi cal exercise regimens but had intact secondary valgus stabilizers. Significant differences in the stiffness of the ligaments in the different groups were not detected. In conclusion, exercise had a beneficial effect on the strength of the medial collateral ligament in stable rat knees but an adverse effect on the laxity of the MCL when the knees had been rendered unstable.