Factors affecting isokinetic muscle strength before and after anterior cruciate ligament reconstruction.

The purpose of this study was to evaluate the factors affecting muscle strength of ACL-deficient knees before and after ACL reconstruction. The study included 122 male patients who underwent primary ACL reconstruction with a bone-patellar tendon-bone autograft. Preoperative loss and change in muscle strength in both extensor and flexor muscle groups after ACL reconstruction were calculated separately at 60 degrees/sec and 180 degrees/sec angular velocities. We evaluated the effect of surgical delay on the preoperative deficit and on its change after surgery. Muscle strength change after ACL reconstruction was also evaluated in relation to patient compliance to treatment. The longer the delay of ACL reconstruction the more the muscle strength deficit of flexor and extensor muscles increased. In the ACL deficient knees with high strength deficit, improvement in muscle strength was higher after ACL reconstruction for both muscle groups. When delay of ACL reconstruction was short and the patient was compliant to treatment, flexor muscle strength recovery was early. Shortening the delay to reconstruction had a positive influence on muscle strength after ACL reconstruction when preoperative muscle strength deficit was high.