This is a study based on a cohort in a register of patients enrolled in a digital osteoarthritis self-management program, Joint Academy. The purpose of this study is to examine joint pain and the potential change of this pain, in patients with long-term adherence to a digital self-management program for individuals with knee- and hip osteoarthritis. The hypothesis, based on preliminary findings is that pain levels of those adhering to the program, decreases over time. To test the hypothesis, participants weekly pain report will be investigated whilst adhering to the digital program for 6- to 12 months, and statistically tests will be performed to find out whether significant differences can be seen over time.

Introduction Osteoarthritis (OA) is highly prevalent in older adults and a growing cause of disability. The importance of availability of primary treatment of OA is gaining momentum, and web-based self-management programs have in recent years become available. Evidence of short term effects of such programs are abundant, yet the evaluation of long term effects of these programs is scarce.

Aim To investigate joint pain development over time from participation in a web-based OA self-management program for people with hip or knee OA.

Methods Participants joined the program through advertisements and campaigns on the web. Included participants had a radiographic or clinical diagnosis of hip or knee OA (about 95%) from a physical therapist or physician. The intervention consisted of a digital, structured and individualized treatment program for people with hip or knee OA (Joint Academy®; www.jointacademy.com). The program consists of neuromuscular exercises appropriately adjusted to each patient in regard to degrees of complexity and difficulty and information in the form of text or video lessons (with quizzes on the material after each episode) on subjects related to OA, OA symptoms and its management.

Outcome measures Joint pain in the hip or knee was assessed at baseline, and weeks 12, 24 and 48 using the Numerical Rating Scale (NRS), a 0-10 scale where 0 is defined as No pain and 10 is defined as Maximum pain. Minimal clinically important change (MCIC) of pain was defined as an improvement of 20%. As a measure of physical function, the 30-second chair stand test (30CST) was used and performed by the patient every other week, using an instruction video with a coupled visual timer. The patient entered the performed number of repetitions after each test. Physical function data was handled similarly to the NRS, with week 24 ±4 adjacent weeks and week 48±6 adjacent weeks included for those with available NRS data. All outcomes were self-assessed, self-centred, and chosen based on the International Consortium for Health Outcomes Measurement Standard Set for Hip & Knee Osteoarthritis (ICHOM).

Statistical analysis Summary data are described by the mean value, standard deviation and number of observations or the number and percent of the categories of interest. The group-specific mean treatment effect of duration on pain and repetitions (30CST - physical function), as well as differences in pain over time between hip and knee OA with or without additional covariates, were estimated and tested using random slopes and intercepts models. Pain development over time was plotted for hip and knee OA respectively.

To describe patients adhering for six months with contrasting pain severity at baseline, participants were divided into same-sized tertiles based on reported baseline pain, with related descriptive data. Mean pain per time point was calculated and plotted for each group. Significance level was set to p<0.05, and p-values and 95% confidence intervals were reported when applicable. Statistical calculations were performed in Statistical Package for Social Sciences (SPSS Version 25, IBM Corporation, New York, USA) and Stata 15.1 (StataCorp LLC, Texas, USA).

Inclusion Criteria:

• radiographic or clinical diagnosis of hip or knee OA (about 95%) from a physical therapist or physician
• had been treated in the digital non-surgical treatment program the first 3 weeks with a adherence of at least 70%
• had been included in the program at least 24 weeks prior to the data extraction

Exclusion Criteria:

-

At the time of the study start (13th of March, 2019), the Joint Academy patient database contained data from 1709 Swedish participants who had reported one of their knees or hips as their most symptomatic joint