Lack of agreement between the participants and lack og funding

This study is the radiological component of an earlier registered trial under the title: Efficacy of Exercise on Physical Function and Cartilage Health in Patients With Knee Osteoarthritis. The main purpose in this component of the study is to evaluate the efficacy of aerobic exercise and strength training on the T2 and T1 rho relaxation times of the articular cartilage. It has been proven that exercise can improve function and reduce the need for analgesics in patients with osteoarthritis. With this study, we wish to investigate if different kinds of exercise can cause measurable improvements in T2 and T1 rho relaxation times of the articular cartilage, and also if this improvements are transient or permanent.

Inclusion Criteria:

• Women and men aged 45-65 years
• Clinical knee OA according to the American College of Rheumatology Clinical Criteria 17
• Kellgren and Lawrence radiographic OA grade 2 and 3 (mild to moderate radiographic OA)

Exclusion Criteria:

• Severe knee OA according to the Kellgren and Lawrence classification (grade 4)
• Other known major musculoskeletal impairments in the lower extremities or the back or prostheses in any joint of the lower extremities
• Known coronary heart diseases or cancer
• Body mass index > 35
• Scheduled for surgery in any joint
• Known mental or psychologic diseases
• Known drug abuse
• Persons who already perform sports related moderate physical activity more than two times a week
• Contraindications for magnetic resonance imaging (specific point list at Diagnostic Imaging Division, Akershus University Hospital)
• Not speaking Norwegian