BACKGROUND: A significant proportion of patients experience functional limitations following total hip and knee arthroplasty (THA and TKA). The purpose of this study was to investigate prospectively the patient-reported and objectively assessed functional recovery following THA and TKA.

METHODS: Patients were recruited at a regional Danish hospital, using a prospective, observational hypothesis-generating cohort design. Primary outcome measures were performance-based function (30-s chair-stand test) and self-reported physical function measured by the Hip Disability and Osteoarthritis Outcome Score (HOOS) for those who had undergone THA, and the Knee Injury and Osteoarthritis Outcome Score (KOOS) for those who had undergone TKA. In addition, patient expectations, the "forgotten joint" scale and pain catastrophizing were measured. Outcome measures were collected at baseline (preoperatively) and at follow-up (4 months postoperatively).

RESULTS: A total of 95 patients (59 who had undergone THA and 36 who had undergone TKA) were recruited. Performance-based function improved only slightly, with a mean difference of 2.9 (95% confidence interval [CI] 1.9, 4.0) for THAs and 1.6 (95% CI 0.4, 2.8) for TKAs. Self-reported physical function improved significantly, with a mean difference of 37.9 (95% CI 31.5, 44.3) for THAs and 28.6 (95% CI 22.7, 34.4) for TKAs. However, dividing the cohort into "improved" and "non-improved" groups based on changes in performance-based function, no clinically relevant predictors for poor performance-based outcome could be found.

CONCLUSIONS: Self-reported outcome measures improved significantly following THA and TKA, whereas performance-based function improved only slightly by the 4-month follow-up. The subgroup that did not improve in performance-based function still reported significant improvements in self-reported outcome measures, demonstrating the difficulty in predicting optimal rehabilitation strategies after THA and TKA.