Function of the quadriceps and hamstrings muscles in knees with chronic partial deficiency of the anterior cruciate ligament. Isometric and isokinetic evaluation.

We assessed the isokinetic and isometric strength and power profile of the knees of 37 patients who had a previous grade II sprain (partial tear) of the anterior cruciate ligament. Of the 37 knees, 11 had an isolated partial anterior cruciate ligament rupture and 26 had a partial anterior cruciate ligament rupture combined with a partial medial collateral ligament rupture. The Cybex II isokinetic dynamometer was used in the measurements. Eight years after the injury, the mean strength deficit of the injured knees was minimal when compared with the uninjured side. In the hamstrings of both groups, 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 (total work, average power, and peak angular impulse) of the injured knees showed some, but not significantly greater, deficits (hamstrings, 7% to 10%; quadriceps, 4% to 10%). We found that the general thigh muscle function in knees with old grade II sprains of the anterior cruciate ligament appears adequate except in flexion where the strength deficits are significantly greater in higher speeds of isokinetic movement. Therefore, rehabilitation using high-speed flexion (and extension) exercises is recommended.