Table 1 Inclusion and exclusion criteria for study participation (t0 = baseline)

Inclusion criteria (all criteria relevant for study eligibility)

 • Insurance holder of the insurance company offering the exercise program since two or more years prior t0

 • Referral from an orthopaedic surgeon or general practitioner

 • Self-reported lifetime prevalence of hip and/or knee OA that was previously diagnosed by a medical practitioner

 • Physical and mental ability to participate in the interventional program and to answer self-administered questionnaires at t0

Exclusion criteria (one or more positive answers lead to non-eligibility)

 • Significant established osteoporosis requiring treatment, previous spontaneous or low impact fracture prior t0

 • Co-morbidities leading to major impairments in everyday life and representing contra-indications for physical activities at t0

 • Artificial joint replacement at the knee and/or hip joint within the last 6 months prior t0

 • Artificial joint replacement at the knee and/or hip joint with instable anchoring at t0

 • Artificial joint replacement at the knee and/or hip joint with rradiologic signs of implant loosening at t0

 • Artificial joint replacement at the knee and/or hip joint accompanied with acute joint inflammation at t0

 • Current pain at rest or with activity due to artificial joint replacement at the knee and/or hip joint

 • Luxation as an adverse event of artificial hip replacement prior t0

 • Surgery at the lower extremity within the last 3 months prior t0

 • Regular use of gait aids

 • Self-reported acute illness at t0

 • < 15 points^a on the WOMAC Index subscale pain (0–100) and < 15 points on the WOMAC Index subscale physical function (0–100) at t0

 • Insufficient German language ability for self-administered questionnaires (IG) at t0

 • Current employment in the health care insurance at t0