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Aim: To study the association between within-person changes in patient-reported outcomes (PROMs) and wish for joint surgery during participation in a digital first-line intervention comprising exercise and education for knee/hip osteoarthritis (OA).

Methods: Retrospective observational registry study. Participants enrolled between 01/06/2018 and 30/10/2021 with follow-up data at 3 months (n=13,961). We used asymmetric fixed effect (conditional) logistic regressions to study the association between change in wish to undergo surgery at last available time point (3,6,9 or 12 months) and improvement or worsening of PROMs pain (0-10), quality of life (EQ5D-5L, 0.243-0.976), overall health (0-10), activity impairment (0-10), walking difficulties (yes/no), fear of movement (yes/no) and Knee/Hip injury and Osteoarthritis Outcome Score 12 Items (KOOS-12/HOOS-12, 0-100) function and quality of life (QoL) subscales.

Results: The proportion of participants wishing to undergo surgery declined by 2% (95% CI 1.9, 3.0), from 15.7% at the baseline to 13.3% at 3 months. Generally, improvements in PROMs were associated with reduced likelihood of wishing for surgery while worsening was associated with increased likelihood. For pain, activity impairment EQ-5D and KOOS/HOOS QoL, a worsening led to a change in the probability of wish for surgery of larger absolute magnitude than an improvement in the same PROM.

Conclusions: Within-person improvements in PROMs are associated with reduced wish for surgery, while worsenings with an increased wish for surgery. Larger improvements in PROMs may be needed to match the magnitude of the change in wish for surgery associated with a worsening in the same PROM.