Factors Associated With Knee Extension Strength Symmetry After Anterior Cruciate Ligament Reconstruction With Quadriceps Tendon Autograft

Background: Diminished postoperative knee extension strength may occur after anterior cruciate ligament reconstruction (ACLR) with quadriceps tendon (QT) autograft. Factors influencing the restoration of knee extensor strength after ACLR with QT autograft remain undefined. Purpose: To identify factors that influence knee extensor strength after ACLR with QT autograft. Study Design: Case-control study; Level of evidence, 3. Methods: The authors performed a retrospective review of patients who underwent primary ACLR with QT autograft at a single institution between 2010 and 2021. Patients were included if they completed electromechanical dynamometer testing at least 6 months after surgery. Exclusion criteria consisted of revision ACLR, <6 months of follow-up, concomitant procedure (osteotomy, cartilage restoration), and concomitant ligamentous injury requiring surgery. Knee extension limb symmetry index (LSI) was obtained by comparing the peak torque of the operated and nonoperated extremities. Univariable and multivariable analyses were performed to identify factors associated with knee extension LSI in the patient, injury, rehabilitation, and preoperative patient-reported outcomes score domains. Results: A total of 107 patients (58 male; mean age, 22.8 years) were included. Mean knee extension LSI of the overall cohort was 0.82 +/- 0.18 at 7.5 +/- 2.0 months; 35 patients (33%) had a value of >= 0.90. Multivariable analysis demonstrated significant negative associations between knee extension LSI and female sex (-0.12; P < .001), increased age at the time of surgery (-0.01; P = .018), and larger QT graft width (-0.049; P = .053). Conclusion: Factors influencing knee extensor LSI after ACLR with QT autograft in this study population spanned patient and surgical factors, including female sex, older age at the time of surgery, and wider graft harvest. Surgeons should consider the association between these factors and lower postoperative knee extensor LSI to optimize patient outcomes.