Patients diagnosed with hand osteoarthritis will be recuited from The Norwegian Rheumatism Association, Diakonhjemmet Hospital and Ankerløkka Legesenter (general practitioner). Patients will be summoned for an appointment at Diakonhjemmet or another suitable place for testing of grip strength and instructions on how to download the app. The e-self-management intervention is a 12 week intervention delivered through the Happy Hands app.

The app is developed based on a combination of behavioural change techniques informed by Social cognitive theory26 and the EULAR recommendations on management of hand OA2. The 12-week intervention consists of 25 short informational videos addressing the themes prioritized by the patient research partners. These themes are further operationalized into the following categories: "Information on hand OA", "Hand exercises", "Use of assistive devices and orthoses", "Medication and surgical alternatives", and "Self-management of the disease". Additionally, the intervention includes a hand exercise program consisting of 8 videos providing instructions on warm up, exercises to improve mobility, strength and coordination, and a stretching exercise. The informational videos and exercise program are delivered in a progressive order across the 12 weeks. When downloading the app, participants are asked to specify when they plan to use the app (three days a week with time points). Thereafter, patients get a notification on their smartphone with that week's informational videos and hand exercises on the specified days.

After each exercise session patients are asked to rate their pain and stiffness, and these answers are put into graphs visualising the development over the 12-week intervention period. Each month, patients also answer questions about hand function, which they can use to self-monitor their development across the intervention period. Encouragement and motivational messages are provided each week to enhance continued adherence to the intervention. Additionally, at the end of each week the patients are asked questions related to the informational videos they have seen that week for the purpose of promoting self-efficacy.

The primary aim is to assess the change in quality indicators from baseline to 12 weeks follow-up. Secondary aims are to assess the change in pain, stiffness, activity performance and grip strength from baseline to follow-up, and to assess the use of and adherence to the content of the app.