Isokinetic evaluation of knee muscles and correlation of maximum torque of the extensors of the operated knee with thigh circumference in soccer players 2 years after ACL reconstruction: A cross-sectional study

Background: Anterior cruciate ligament reconstruction (ACLR) often results in residual strength deficits in knee muscles, which may affect an athlete's return to performance. Isokinetic testing and thigh circumference measurements offer valuable insights into recovery, with thigh circumference potentially serving as a quick indicator of quadriceps strength. Objectives: To evaluate the isokinetic capability of knee extensors and flexors two years after ACLR and examine the correlation between isokinetic peak torque of knee extensors and thigh circumference of the operated limb. Methods: Seventeen professional soccer players, two years post-ACLR, participated. Thigh circumference was measured at 10cm and 20cm from the patella. The peak torque of knee flexors and extensors was assessed at various speeds. Hamstring-to-quadriceps ratios (H/Qconv and H/Qfunc) were evaluated. Paired-Samples T Test compared peak torque, thigh circumference, H/Qconv, and H/Qfunc between limbs. Pearson Correlation determined the relationship between peak torque of knee extensors and thigh circumference. Results: Two years post-ACLR, peak torque was significantly reduced for knee extensors at 60(degrees)/s, 180(degrees)/s, and 300(degrees)/s (p<0.05) and for knee flexors at 60(degrees)/s (p=0.038). No significant differences were found for H/Qconv and H/Qfunc. Thigh circumference differed significantly at 20cm from the patella (p=0.030) and correlated with the peak torque of knee extensors (r=0.770-0.863). Conclusions: Knee extensors and flexors show reduced peak torque two years post-ACLR. A strong correlation exists between peak torque of knee extensors and thigh circumference. Isokinetic evaluation is effective at functional velocities, and thigh circumference measurement is a viable alternative for assessing quadriceps strength.