This study will investigate outcomes of a 3-month first-line treatment program for hand osteoarthritis, using data from the Swedish Osteoarthritis Registry.

According to international guidelines, exercise, education and splinting (if needed) should constitute first-line treatment for people with hand osteoarthritis (OA). However, few studies have investigated the outcomes of such treatment in individuals with hand OA. In this retrospective register-based study we will investigate the outcomes of 3-months participation of first-line treatment for hand OA using data from the Swedish Osteoarthritis register (SOAR). Outcomes will be self-reported change in pain, pain frequency, health-related quality of life, physical activity, fear of movement and willingness for joint surgery between baseline and three months follow-up. In addition, we will investigate if potential improvements remain at 12 months.

Statistical analysis Changes in continuous variables between baseline and the two follow-ups (3 and 12 months) will be analyzed using paired T-test. Changes in proportions in the categorical variables will be analyzed using McNemars test for pairwise comparisons. Standardized effect sizes will be reported as Cohen's d with the following cut offs: 0.2=small, 0.5=medium and 0.8=large effect size. All outcomes will be analyzed separately for females and males.

In this study we will include all participants registered in SOAR fulfilling the eligibility criteria outlined below (n>1000) and consequently no power calculation was performed.

Inclusion Criteria:

• 1) a clinical diagnosis of hand OA, 2) Participated for three months in the program 3) reported any of the included outcomes at both baseline and at 3 months follow-up.

Exclusion Criteria: None

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Patients with hand osteoarthritis registered in the Swedish Osteoarthritis register. The Swedish Osteoarthritis register is a national quality register evaluating the effect of first-line treatment on osteoarthritis-related outcomes.

De-identified IPD for primary and secondary outcomes will be made available upon reasonable request.

The data used in this study contains sensitive information about the study participants and they did not provide consent for public data sharing. The current approval by the Regional Ethical Review Board, Sweden does not include data sharing. A minimal data set could be shared by request from a qualified academic investigator for the sole purpose of replicating the present study, provided the data transfer is in agreement with EU legislation on the general data protection regulation and approval by the Swedish Ethical Review Authority.