Changes in Muscle Torque during 4 Years after Total Knee Arthroplasty

Purpose: The purpose of our study was to determine the changes of muscle torque before and during 4 years after total knee arthroplasty (TKA) prospectively. Material and Methods: This study included 17 patients which were treated only on one leg with a total knee arthroplasty. Isokinetic torque measurements during knee movements with different velocities were done before, 2, 4 and 48 months after implantation of TKA. Results: The isokinetic torque measurements with low velocity (60 degrees/s) and high velocity (180 degrees/s) showed statistically significant (p < 0.05) higher values on the operated knee 4 months after the operation. Significant higher values were reached on the contralateral leg, too. During high velocity there were still deficits compared with the preoperative values. The increase in muscle torque was retarded in extension compared to flexion. This was indicated in a shift of the flexion/extension ratio towards flexion. This ratio reached nearly physiological values after 48 months. Only during high velocity on the operated leg the flexion/extension ratio was still slightly increased. The torque values on the non operated leg at the 48 month-follow-up were significantly lower (p < 0.05) than 2 and 4 months after the operation. Diskussion: The main increase in muscle torque was found later than 2 months after the operation. 4 months postoperatively there were still pathologic values of the flexion/extension - ratio. Conclusion: This indicates that the training of muscle power should be continued over the first. 2 postoperative months over a longer period.