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BACKGROUND: The benefits of exercise in patients with knee osteoarthritis are well documented, but the optimal exercise dose remains unknown.

OBJECTIVE: To compare high-dose versus low-dose exercise therapy with regard to knee function, pain, and quality of life (QoL) in patients with long-term symptomatic knee osteoarthritis.

DESIGN: A Swedish and Norwegian multicenter randomized controlled superiority trial with multiple follow-ups up to 12 months after the intervention. (ClinicalTrials.gov: NCT02024126).

SETTING: Primary health care facilities.

PATIENTS: 189 patients with diagnosed knee osteoarthritis and a history of pain and decreased knee function were assigned to high-dose therapy (n = 98; 11 exercises; 70 to 90 minutes) or low-dose therapy (n = 91; 5 exercises; 20 to 30 minutes).

INTERVENTION: Patient-tailored exercise programs according to the principles of medical exercise therapy. Global (aerobic), semiglobal (multisegmental), and local (joint-specific) exercises were performed 3 times a week for 12 weeks under supervision of a physiotherapist.

MEASUREMENTS: The Knee Injury and Osteoarthritis Outcome Score (KOOS) was measured biweekly during the 3-month intervention period and at 6 and 12 months after the intervention. The primary end point was the mean difference in KOOS scores between groups at the end of the intervention (3 months). Secondary outcomes included pain intensity and QoL. The proportion of patients with minimal clinically important changes in primary and secondary outcomes was compared between groups.

RESULTS: Both groups improved over time, but there were no benefits of high-dose therapy in most comparisons. One exception was the KOOS score for function in sports and recreation, where high-dose therapy was superior at the end of treatment and at 6-month follow-up. A small benefit in QoL at 6 and 12 months was also observed.

LIMITATION: There was no control group that did not exercise.

CONCLUSION: The results do not support the superiority of high-dose exercise over low-dose exercise for most outcomes. However, small benefits with high-dose exercise were found for knee function in sports and recreation and for QoL.