Thigh muscle function after partial tear of the medial ligament compartment of the knee. The purpose of the study was to assess the isokinetic and isometric strength and power profile of the knees of 48 patients who had a previous second-degree sprain (partial tear) of the medial ligament compartment, the most common knee ligament injury in sports. The CYBEX II isokinetic dynamometer was used in the measurements. On an average of 8 yr after the injury, the mean strength deficit of the injured knees was minimal: 4 +/- 5% (range 0-28%) in extension and 2 +/- 4% (0-20%) in flexion. The average strength score (max. 100 points) was 90 +/- 11 (56-100), representing an excellent classification. In hamstrings, the relative strength deficit increased significantly with a higher speed of isokinetic movement (P less than 0.05). Compared with the strength parameters (peak torques), the other functional parameters of the injured knees (total work, average power, and peak torque acceleration energy) showed some but not significantly greater deficits (hamstrings 9-11%, quadriceps 6-8%). In conclusion, the general thigh muscle function in knees with old second-degree sprain of the medial ligament compartment appears good and acceptable, but the strength deficits are systematically greater in higher speeds of isokinetic movement. Therefore, rehabilitation utilizing high speed extension and flexion exercises is recommended. 