To investigate whether measured and patient-perceived function 6 months after total knee replacement (TKR) can be predicted from factors measured during post-operative rehabilitation.
Retrospective analysis of data from a randomised clinical trial involving 100 patients after TKR. High- and low-performing subjects for pain, WOMAC score and 6-min walk test (6MWT) at 2, 8 and 26 weeks post-TKR were partitioned and analysed. Multiple stepwise regression analysis was applied to the contributing factors to determine associations with outcome.
Prediction of outcome was unconvincing based upon variables recorded at 2 weeks; however, status at 8 weeks was a better indicator of functional performance and perception at 26 weeks. 6MWT at 26 weeks could be predicted from VAS pain scores and 6MWT at 8 weeks (r = 0.789; p < 0.001). Prediction of pain and patient perceived function at 26 weeks was also dependent on performance in 6MWT at 8 weeks (r = 0.51; p < 0.05). Males and those with lower body mass index values demonstrated better functional outcomes.
Functional status at 2 weeks post-surgery gives few indicators of ultimate status, possibly because of pain, joint swelling and other immediate post-operative factors. However, measurements taken at 8 weeks, following an outpatient-based exercise programme, provides a reasonable estimate of performance and response 26 weeks after surgery. Patient and clinician expectations for longer-term recovery could be informed by these findings.