Evaluating Thigh Muscle Volume and Compensatory Muscle Changes in Bone–Patellar Tendon–Bone, Hamstring Autograft, and Allograft Anterior Cruciate Ligament Reconstructions: A Minimum 5-Year Follow-up

Background: Graft selection in anterior cruciate ligament reconstruction (ACLR) may lead to long-term, graft-specific muscle adaptations, yet their effect on functional outcomes remains poorly understood. Magnetic resonance imaging (MRI)-based 3D modeling enables precise quantification of muscle volume changes, offering insight into the relationship between postoperative muscle preservation and patient-reported outcomes. Purpose: To radiologically evaluate thigh muscle volume changes and patient-reported outcomes at minimum 5-year follow-up among patients after primary anterior cruciate ligament reconstruction (ACLR) using allograft, bone-patellar tendon-bone autograft (BPTB), or hamstring autograft (gracilis and semitendinosus; HS) with MRI-based 3D modeling. Study Design: Cohort study; Level of evidence, 3. Methods: tests and chi-square tests were used for statistical analysis. Results: = 0.48). No covariate (age, sex, BMI, graft type) independently influenced IKDC score. Conclusion: Five years after ACLR, thigh muscle adaptation depended on graft choice and carried meaningful functional consequences. Hamstring autografts were associated with lasting atrophy of the semitendinosus and gracilis with compensatory hypertrophy of the semimembranosus, whereas BPTB autografts were associated with selective loss of the vastus intermedius and no compensatory enlargement in the remaining quadriceps. Across all patients, larger differences in muscle volume between limbs, especially in the anterior compartment, were linked to lower IKDC scores.