Comparison of Differences in Thigh Muscle Morphology and Function according to Post-anterior Cruciate Ligament Surgery Period

PURPOSE: Quadriceps muscle weakness caused by muscle atrophy is a typical feature of individuals who undergo anterior cruciate ligament reconstruction. Although many studies have suggested an acceptable timing for returning to sports after anterior cruciate ligament reconstruction, there are still many controversies. Therefore, this study aimed to present an evidence-based recommendation for returning to sports after anterior cruciate ligament reconstruction by evaluating muscle size and function 9 months after the reconstruction.METHODS: Eighteen patients who underwent anterior cruciate ligament reconstruction were evaluated for quadricep thickness and isokinetic knee extension strength in both limbs. The Mann-Whitney U test was used to compare the differences 1) in thigh muscle thickness and isokinetic knee extension strength between the reconstructed limbs in “more than 9 months after surgery” and “less than 9 months after surgery” groups and 2) between the limb symmetry index of the two groups.RESULTS: The main findings were that the vastus medialis thickness and isokinetic knee extension strength for the reconstructed limbs were significantly greater in the more than 9 months after surgery group (vastus medialis: Z=12.00, p=.014; strength: Z=16.00, p=.034). The vastus medialis and vastus intermedius thicknesses in the more than 9 months after surgery group also showed a significant increase compared to those in the less than 9 months after surgery group (vastus medialis: Z=10.00, p=.006; vastus intermedius: Z= 10.00, p=.006).CONCLUSIONS: After anterior cruciate ligament reconstruction, selective muscle atrophy and weakness in the quadriceps muscles were observed. This study emphasizes the need for targeted early rehabilitation of specific quadriceps muscles to prevent muscle atrophy and weakness after anterior cruciate ligament reconstruction.