Reliability of a peak knee extensor and flexor torque protocol: A study of post ACL reconstructed knees

The purpose of this study was to evaluate the reliability of a strength testing protocol on a sample of patients who had undergone reconstruction of their anterior cruciate ligament. The reconstructed and contralateral knees of 50 patients were assessed by four maximum concentric knee extension and flexion movements (30 second rest in flexion) peformed at a velocity of 60°/second. A difference in peak torque between the post reconstructed and contralateral limb was identified for knee extension, but not for knee flexion. Intraclass correlation coefficients were 0.97 and .096 for the extensor and flexor data respectively. A statistically significant ascending trend in peak torque across trials was identified for the knee extensor torques, but not for the knee flexor torques. This trend was significantly greater for the torques obtained on the involved limbs compared to those of the contralateral limbs. Because the results of this study demonstrated a trend in peak torque, while similar investigations on health knees have not, one is cautioned against generalizing the results of measurement protocols validated on healthy knees to those of patient groups.