Gender, preoperative function, and other variables were explored as predictors of recovery after total hip and knee arthroplasty. One hundred fifty-two subjects (63.8 +/- 10.2 years) were repeatedly assessed in the first 4 postoperative months. Average recovery curves for the Western Ontario and McMaster Universities Osteoarthritis Index, 6-minute walk test, and timed up and go test were characterized using hierarchical linear modeling. Recovery predictors were sequentially modeled after validation of the basic developmental models. Gender was a significant predictor (P < or= .003) of physical performance measure scores 1 week after surgery. Thereafter, men and women had similar rates of improvement. Preoperative score was a significant predictor (P < or= .001) in all models. Patients' and surgeons' expectations of outcome need to take preoperative function into account.