Joint angle-specific impairments in rate of force development, strength, and muscle morphology after hamstring autograft

The purpose of this study was to analyze the effects of anterior cruciate ligament reconstruction (ACLR) using the semitendinosus (ST) tendon autograft technique on knee flexor maximal torque and rate of torque development (RTD) in athletes who had returned to competition, and to determine the relationship between knee flexor strength deficits and hamstring muscle cross-sectional area (CSA). Fifteen athletes with ACLR (1.9 +/- 0.6 years post-surgery) and non-injured, sex-matched, and sport-matched control athletes performed maximal voluntary contractions (MVC) of isometric knee flexion to obtain maximal torque (Torque(max)) and maximal RTD (RTDmax) at 5 knee joint angles. CSA of the knee flexors was measured using ultrasound imaging. Deficits were found at all knee joint angles for Torque(max) and more than 70 degrees of knee flexion for RTDmax when comparing the ACLR limb to the Contralateral limb (P < .05). ST muscle CSA was lower in the ACLR limb compared with the Contralateral limb at all measurement sites (P < .01). Correlations (r = 0.6-0.9) were found between ST muscle CSA and knee flexor strength. These results suggest the importance of preserving ST muscle architecture following ACLR. Further, graft choice should be made with consideration of the specific strength requirements of the athlete's sport.

Automated summary

The study analyzed the effects of ACL reconstruction using the semitendinosus tendon autograft technique on knee flexor maximal torque and rate of torque development in athletes who had returned to competition. It found deficits in torque and rate of torque development in the ACLR limb compared to the contralateral limb, and lower semitendinosus muscle cross-sectional area in the ACLR limb. The results suggest the importance of preserving semitendinosus muscle architecture following ACL reconstruction and considering specific strength requirements of the athlete's sport when choosing a graft.