Sex-based differences in isokinetic strength recovery and functional outcomes after hamstring autograft ACL reconstruction

Sex-related differences in neuromuscular recovery may influence rehabilitation after anterior cruciate ligament reconstruction (ACLR). Evidence on longitudinal strength recovery and functional outcomes stratified by sex after hamstring autograft ACLR is limited. This prospective comparative study included 50 patients (25 males, 25 females) undergoing primary hamstring autograft ACLR at a tertiary centre. Isokinetic hamstring and quadriceps strength at 60°, 90° and 180°/s and functional outcomes (International Knee Documentation Committee [IKDC], Tegner, Lysholm scores) were assessed preoperatively and at 3, 6 and 12 months postoperatively. Repeated-measures ANOVA evaluated time effects; between-sex differences were tested with (Welch) t-tests; sex×time interaction was assessed via RM-ANOVA. Baseline characteristics were comparable between sexes (age 24.9 ± 4.1 vs. 25.8 ± 4.3 years). Preoperatively, no significant sex differences were observed in Lysholm (74.5 ± 5.5 vs. 72.0 ± 5.8), IKDC (49.5 ± 8.8 vs. 47.5 ± 9.2) or Tegner (5.9 ± 1.2 vs. 5.7 ± 1.2). At 6 months, males scored significantly higher for Lysholm (95.0 ± 3.6 vs. 92.5 ± 3.6; p=0.018) and IKDC (82.0 ± 6.0 vs. 78.0 ± 6.3; p=0.026), with differences diminishing by 12 months (Lysholm 98.5 ± 3.0 vs. 96.5 ± 3.2; p=0.027; IKDC p≈0.10). Tegner scores showed no significant sex differences (p>0.48). Males demonstrated consistently higher hamstring torque across all velocities with significant sex×time interaction (p<0.05), whereas quadriceps recovery showed parallel improvement. Females had higher hamstring–quadriceps ratios at baseline and early high velocities, with differences disappearing by 12 months. Higher preoperative hamstring strength predicted better mid-term functional outcomes in both sexes. Female patients exhibited slower hamstring strength recovery and transiently lower functional outcomes compared with males after hamstring autograft ACLR, with differences most pronounced at 6 months but largely converging by 12 months. These findings support sex-specific rehabilitation strategies and objective testing for return-to-sport decisions.