Abstract
OBJECTIVES: To investigate whether the association between pain intensity and willingness to undergo surgery is explained by walking difficulties, in patients with knee or hip osteoarthritis (OA). METHODS: This is an observational study using data from the Better management of patients with Osteoarthritis (BOA) register, which collects data from a publicly financed self-management programme for people with OA in Sweden. We included all patients with knee or hip OA who attended the baseline visit between 2008 and 2016. We conducted separate mediation analyses within a counterfactual framework to estimate the mediation effect of walking difficulties (yes/no) on willingness to undergo surgery (yes/no) for each one-point increase in pain (0-10 on a numeric rating scale), adjusted for relevant confounders. RESULTS: We included 72,131 patients (69% women, mean age 66, mean pain 5.4, 81% had walking difficulties, 27% was willing to undergo surgery). A one-point increase in pain intensity was associated with 1.53 (95% CI: 1.51; 1.55) higher odds of being willing to undergo surgery. Walking difficulties mediated 10%-25% of the effect of one-point increase in pain when pain was <8/10, while at pain ≥8/10 this percentage decreased to 3%. CONCLUSIONS: More than 80% of the BOA patients have mild to moderate pain (<8/10) and walking difficulties can mediate up to a quarter of the total effect of pain on the willingness to undergo surgery in these patients. Trials to evaluate the potential to lower surgery demand by reducing walking difficulties in people with these characteristics are needed.