The association between body weight changes and physical activity after anterior cruciate ligament reconstruction

Context: Recovery after anterior cruciate ligament reconstruction (ACLR) can lead to weight gain and reduced physical activity (PA), potentially increasing long-term health risks. Understanding the relationship between PA patterns and weight changes post-ACLR is essential for optimizing rehabilitation strategies. Objective: To examine the relationship between weight changes and PA patterns in the first six months following ACLR. We hypothesized that lower PA levels and greater sedentary time would predict greater weight gain. Design: Case series. Setting: Participants were recruited before ACLR was performed from an academic hospital and a private sports medicine clinic and assessed in a clinical and research setting. Patients or Other Participants: Sixty-one individuals (ages 13–35 years) who underwent primary ACLR were included. Exclusion criteria were prior ipsilateral knee injury/surgery, body mass index (BMI) >35 kg/m², and concomitant posterior cruciate ligament or cartilage surgery. Main Outcome Measure(s): Body weight was measured preoperatively, at 10.4±2.4 weeks (early-phase) and at 26.9±2.6 weeks (mid-phase) after ACLR. PA levels, including daily steps, moderate-to-vigorous PA (MVPA), and sedentary behavior, were assessed using accelerometry. A two-way mixed (time by sex) ANOVA analyzed weight changes, and logistic regressions evaluated whether early- and mid-phase PA levels, age, and sex predicted significant weight gain (≥5%) after ACLR. Results: Males gained more weight (3.4±4.6 kg, p<0.001) than females (1.1±2.9 kg, p=0.030). Logistic regression models incorporating PA predictors were significant (early-phase: χ 2 (5)=13.058, p=0.023; mid-phase: χ 2 (5) =13.003, p=0.023). Males had 5.117-7.622 times higher odds of ≥5% weight gain than females. However, PA levels, sedentary behavior, and age did not significantly predict weight gain. Conclusions: Weight gain is common six months after ACLR, with males experiencing greater increases than females. Although PA and sedentary behavior did not predict weight changes, incorporating targeted weight management strategies, including nutritional and metabolic health interventions, into ACLR rehabilitation may help optimize recovery.