PURPOSE: To examine the effects of timing of anterior cruciate ligament (ACL) reconstruction on the odds to recover muscle (quadriceps and hamstring) strength, return to preinjury physical activity level, and achieve rehabilitation goals at 12 months follow-up. METHODS: Data were extracted from a local rehabilitation registry in Sweden in November 2023. Patients ≥16 years old who underwent primary ACL reconstruction with hamstring tendon autografts, who underwent isokinetic muscle strength assessment, and responded to patient-reported outcomes 12 months after surgery were included. A multivariable logistic regression analysis was used to analyze the association between timing of ACL reconstruction and the recovery of muscle strength, return to preinjury physical activity level, and achievement of rehabilitation goals. The results of the logistic regression analysis were expressed as odds ratios for every 1-unit increase in the predictor variable (months between ACL injury and reconstruction). RESULTS: In total, 715 patients were included, of whom 53.4% (n = 383) were women. The mean age at ACL reconstruction was 28.3 ± 10.5 years, and the median time between ACL injury to reconstruction was 4.9 months (interquartile range [IQR] 2.9-9.4). Delayed ACL reconstruction significantly decreased the odds of returning to preinjury physical activity level at 12 months in patients with a Tegner score of 6-10 (odds ratio 0.97
95% confidence interval 0.94-0.99, P = .009), regardless of age. Shorter median time in months from ACL injury to reconstruction was observed for patients who returned to preinjury physical activity level, especially in younger patients (16-30 years old) (3.9 [IQR 2.5, 6.5] vs 4.7 [IQR 2.9, 9.1], P = .007) and in patients who participated in pivoting activities (Tegner scale 6-10) preinjury (3.4 [IQR 2.3, 6.2] vs 5.0 [IQR 2.9, 9.7], P <
.001). CONCLUSIONS: Delayed ACL reconstruction reduces the odds of returning to preinjury physical activity level in patients active in pivoting activities preinjury (Tegner 6-10), regardless of age, 12 months after surgery. LEVEL OF EVIDENCE: Level III, retrospective study.