Does free-living physical activity improve one-year following total knee arthroplasty in patients with osteoarthritis: A prospective study.

Objective: Total knee arthroplasty (TKA) is the gold-standard treatment for end-stage knee osteoarthritis, and the primary expectations are reduced pain and improved function. However, there is conflicting evidence regarding functional changes post-TKA. Commonly, functional changes are measured using Oxford Knee Score (OKS). No previous study has investigated physical behaviour (PB) changes in terms of volume and patterns post-TKA. The aims of this study were to explore volume and pattern changes in PB following TKA using an objective tool and to assess the correlation between this and OKS.

Design: An activPAL measured the PB of individuals on a waiting list for TKA for a period of 7-8 days pre-TKA, and for the same length of time at 12 months post-TKA. OKS was completed at similar follow-up time points.

Results: Thirty-three individuals completed the study, where stepping time, the number of steps and the time spent on moderate to vigorous physical activity (MVPA) (>100 steps/minute) improved significantly post-TKA  = 0.0001. Steps at 12 months post-TKA improved by 45.6% (from 4240 to 6174) and stepping time increased by 38.8% (from 0.98 to 1.36 h). MVPA improved by 35 min at 12 months (from 6.6 to 41.7 min). There were no significant correlations between PB and OKS.

Conclusion: This is the first study to explore PB volumes and event-based patterns post-TKA. Activity improved in terms of volume and patterns. No correlation was found between OKS and ActivPAL, which emphasises the need to use objective methods in addition to patient-reported outcome measures.