Adherence to early mobilization and acute functional recovery after lower-limb orthopedic surgery: A longitudinal cohort study

Objectives: To quantify the relationship between exercise adherence to early mobilization and short-term functional trajectory after lower-limb orthopedic surgery, and to identify determinants of adherence. Methods: Longitudinal cohort study of 281 adults undergoing primary hip or knee arthroplasty or acute internal fixation of lower-extremity fractures. Adherence at discharge was measured with the exercise adherence rating scale (EARS). The primary outcome was change in the normalized total Western Ontario and McMaster Universities osteoarthritis index (WOMAC) (0–100 scale; higher = worse; positive change = improvement) from baseline to discharge. Analysis of covariance (ANCOVA) was used to analyze WOMAC change, with baseline severity as a covariate; multivariable linear regression was used for EARS predictors. Variance inflation factors, bootstrap confidence intervals (1000 resamples), a pre-specified adherence × surgery interaction, and E-value sensitivity were applied. Results: After ANCOVA adjustment, a threshold pattern was observed: Medium versus low adherence showed significant additional WOMAC improvement (β = 0.19, 95% confidence interval [CI] 0.02–0.36; p = 0.029); high versus low showed a similar magnitude with marginal significance (β = 0.20, 95% CI −0.02–0.42; p = 0.073). The adherence effect was driven by the fracture subgroup (interaction p = 0.014). Hypertension predicted higher adherence (β = 3.71, p < 0.0001) yet lower WOMAC improvement (β = −0.80, p < 0.0001). Education was independently associated with adherence. Conclusion: Early-mobilization adherence showed a small threshold-like association with short-term functional trajectory, modified by surgical context. A substantial WOMAC floor effect limits the interpretation of acute postoperative functional change.