Isokinetic Knee Extension and Flexion Strength in Female Athletes at 20 and 40 Weeks After Bone–Patellar Tendon–Bone Anterior Cruciate Ligament Reconstruction

Klemola, SE, Gorman, BT, Welch, N, and Kung, SM. Isokinetic knee extension and flexion strength in female athletes at 20 and 40 weeks after bone-patellar tendon-bone anterior cruciate ligament reconstruction. J Strength Cond Res 39(9): e1075-e1080, 2025-Despite females' higher anterior cruciate ligament (ACL) injury risk, research assessing the rehabilitation of knee extensor and flexor strength after an ACL reconstruction (ACLR) with a bone-patellar tendon-bone (BPTB) graft in female athletes is limited. The purpose of this study was to investigate the restoration of knee extension strength in female athletes after ACLR with a BPTB graft, along with knee flexion strength, limb symmetry index (LSI), and return to sport (RTS) status. Eighty-nine 16-30-year-old female athletes who underwent a BPTB ACLR were eligible for analysis. Participants completed isokinetic knee extension and flexion strength testing at 20 ± 5 (T1) and 40 ± 5 (T2) weeks post-ACLR using an isokinetic dynamometer. Changes in peak knee extension and flexion torques, and LSI values were assessed in the injured and noninjured limbs from T1 to T2. RTS status was recorded at T2. Two-way repeated measures ANOVA analyzed peak extension and flexion torques and paired t-tests analyzed LSI. Statistical significance was set at p ≤ 0.05. Compared with the injured limb, the noninjured limb demonstrated a higher peak extension torque at T1 ( p < 0.0001) and T2 ( p < 0.0001) and a higher peak knee flexion torque at T1 only ( p = 0.004). Peak knee extension ( p < 0.0001) and flexion ( p = 0.03) torque LSI were significantly higher at T2 than at T1. Despite significant improvements in knee extension and flexion strength, a deficit in the injured limb's knee extensor strength remained at 40 weeks postsurgery, which highlights the need for female athletes to prioritize strengthening the injured limb's knee extensors during rehabilitation, especially before returning to training and/or competition.