Rectus femoris graft harvest for anterior cruciate ligament reconstruction does not result in selective rectus femoris muscle volume loss or strength deficit at one year: quantitative magnetic resonance imaging, isokinetic and functional analyses

Purpose To evaluate 1-year clinical and functional outcomes, as well as donor-site morbidity based on quadriceps muscle morphology, after primary single-bundle ACLR using a quadrupled RF tendon autograft. Methods Patients who underwent primary single-bundle ACLR using a quadrupled RF tendon autograft with adjustable suspensory fixation between December 2024 and April 2025 were retrospectively reviewed. Clinical outcomes were assessed using the International Knee Documentation Committee Subjective Knee Form (IKDC), Marx Activity Scale, KT-1000 arthrometer side-to-side difference, and pivot-shift test. Quadriceps muscle volumes, including RF, vastus medialis (VM), vastus lateralis (VL), and vastus intermedius (VI), were measured using magnetic resonance imaging (MRI) at one year postoperatively. Isokinetic strength testing at 60°/s and 240°/s and hop performance tests were performed to determine limb symmetry indexes (LSI). Results A total of 54 patients were evaluated with a mean follow-up of 15.7 ± 4.2 months. The mean IKDC score was 84.1 ± 9.7, the mean Marx Activity Scale score was 7.1 ± 3.2, and the mean side-to-side anterior tibial translation difference was 1.8 ± 1.2 mm. All quadriceps muscle volumes were significantly lower in the operated limb than in the contralateral limb ( p < 0.001). Mean deficits were 9.63% for RF, 8.52% for VL, 7.95% for VI, and 8.08% for VM. No significant difference was observed among the percentage deficits of the four muscles (F = 1.701, p = 0.170). LSI values exceeded 90% in all evaluated strength and functional parameters. No significant side-to-side differences were found in most isokinetic and hop tests, except for 240°/s extension strength ( p = 0.03) and triple-hop performance (p < 0.001). Conclusion Primary ACLR using a quadrupled RF tendon autograft resulted in favourable one year clinical and functional outcomes with restoration of limb symmetry. Quantitative MRI analyses demonstrated that RF graft harvest did not result in selective RF muscle volume loss or clinically relevant strength deficit at one year postoperatively.