Postoperative Quadriceps Symmetry, Knee Laxity, and Single-Leg Hop Performance in Association with 24-Month Ipsilateral Graft Retear After Anterior Cruciate Ligament Reconstruction: A Cohort Study

Background: Ipsilateral graft retear after anterior cruciate ligament reconstruction (ACLR) remains a major concern in athletes, while the relationship between postoperative mechanical and functional measures and retear remains uncertain. Methods: This cohort study included 48 athletes after primary unilateral ACLR with hamstring-tendon autograft. Follow-up was scheduled at 6, 9, and 12 months (184 ± 13, 276 ± 17, and 368 ± 22 days), and the analytic export retained one postoperative value per athlete for GNRB side-to-side laxity at 250 N, concentric isokinetic quadriceps limb symmetry index (LSI) at 60°/s, single-leg hop-for-distance LSI, and patient-reported outcomes, without preserving the originating visit. MRI-confirmed ipsilateral graft retear was recorded within 24 months after clinically suspected reinjury; retear dates were not retained. Results: Fourteen athletes (29.2%) sustained a retear. Quadriceps LSI was lower in the retear group than in the no-retear group (81.3 ± 7.5% vs. 88.1 ± 9.0%; p = 0.011), and each 1-SD higher quadriceps LSI was associated with lower retear odds (OR 0.43, 95% CI 0.21–0.89). In an exploratory threshold analysis, quadriceps LSI < 85% was associated with a higher retear proportion (RR 3.21, 95% CI 1.17–8.82). Associations for knee laxity, hop performance, and patient-reported outcomes were not statistically robust. Conclusions: Postoperative quadriceps symmetry showed the clearest association with 24-month graft-retear status. However, because the originating measurement visit and retear dates were unavailable, temporal precedence could not be established, and the exploratory <85% LSI finding should not be interpreted as a validated return-to-sport threshold.