Improvements in objectively measured activity behaviours do not correlate with improvements in patient-reported outcome measures following total knee arthroplasty

Abstract Background Activity monitors have added a new dimension to our ability to objectively measure physical activity (PA) in patients undergoing total knee arthroplasty (TKA). The aim of the study was to assess whether changes in the time spent sitting, standing and stepping were associated with changes in patient-reported outcome measures (PROMs) before and after TKA. Methods Valid activPAL data (>3 three days) and PROMs were obtained from 49 men and women (mean (SD) age: 62.8 (8.6) years, BMI: 33.8 (7.1) kg/m2) who underwent primary TKA, before and at six weeks or six months after surgery. Patient reported symptoms of pain, stiffness and knee function were obtained using the Knee injury and Osteoarthritis Outcome Score (KOOS) and Oxford Knee Score (OKS) questionnaires. Results Mean (SD) KOOS (80.1 (16.3) to 41.6 (6.5), p 0.05). Conclusion Despite improvements in self-reported knee pain and functional ability, these changes do not correlate with improvements in objectively measured light intensity and sedentary activity behaviours.