Significant Deficits Are Seen in Extensor Muscle Performance but Not Flexor Muscle Performance 6 Months After Anterior Cruciate Ligament Reconstruction Using a Rectus Femoris Tendon Autograft

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Abstract
Purpose: To evaluate bilateral isokinetic performance symmetry of knee extensors and flexors 6 months after anterior cruciate ligament reconstruction using a rectus femoris tendon autograft. Methods: This retrospective case series included patients consecutively recruited at a single tertiary sports medicine center between January 2023 and July 2024. Inclusion required primary anterior cruciate ligament reconstruction with a rectus femoris autograft, no prior knee surgeries, and a minimum 6‐month follow‐up; patients with revision or multiligamentous procedures were excluded. Isokinetic testing was performed at 6 months using a computerized dynamometer. The nonoperative limb was tested first, followed by the operative limb. Patients performed 5 maximal effort trials at 60°/s for both extension and flexion. Measured outcomes included peak torque (PT), PT normalized to body weight, angle at PT, total work (TT), and mean power (PM) for both knee extension and flexion. Paired t‐tests compared operated and nonoperated limbs. Statistical significance was set at P ≤ .05. Results: Thirty‐one male patients (mean age, 26.3 ± 4.7 years) were included, with a mean follow‐up of 6.2 ± 0.4 months. At 6 months, the operated limb achieved 71% of contralateral PT and 75% of contralateral PM, with significant deficits in extension PT ( P < .001), PT normalized to body weight ( P < .001), TT ( P < .001), and PM ( P = .002), while no significant difference was found for angle at PT ( P = .457). Flexor performance showed near‐complete recovery, with the operated limb reaching 93% of contralateral peak torque and 90% of TT, with P = .355, .340, .902, .153, and .316 for PT, PT normalized to body weight, angle at PT, TT, and PM, respectively. Conclusions: At 6 months, anterior cruciate ligament reconstruction with a rectus femoris autograft was associated with complete recovery of knee flexor performance but persistent deficits in knee extensor performance. Level of Evidence: Level IV, retrospective case series.

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