Obesity and osteoarthritis (OA) co-exist in an increasing part of the population.

The two diseases intertwine in several ways. The evolution in the population shows a tendency towards deterioration of both by increasing general age and weight. The two diseases share pathogenetic features and the development of one disease increases the risk of the other and may be the onset of a vicious circle.

There is a link between treatments of these two diseases as well. There is now solid (gold) evidence that by treating effectively the obesity of patients with co-occurring OA, the functional status is dramatically ameliorated; the short-term results are equal to that of a joint replacement. The long-term efficacy of a weight loss remains to be shown. OA is definitely one of many diseases in which obesity must be taken seriously into account when planning a correct treatment of patients. This trial has two phases, the first (16 weeks) consisting of a dietary intervention with low-energy diet and the second (52 weeks) a randomized, three group (each n>50 patients) controlled study of maintenance of weight loss by either continuing dietary instruction, exercise, or a control group. The hypothesis is that maintenance of an initially induced weight loss is dependent on attention rather than any specific therapy.

Any patient with osteoarthritis (OA)of the knee and concomitant obesity will be considered for participation. Eligible for this study will be patients with radiographical knee OA. Exclusion criteria are recent or planned knee operations, alloplasties in both knees, ongoing or planned alternative interventions against obesity.

Inclusion Criteria:

• BMI >=30
• Radiographical knee OA
• Age >=50
• Spoken Danish
• Motivated for weight loss

Exclusion Criteria:

• Bilateral Alloplasty of the knees
• Ongoing or planned surgery
• Ongoing or planned alternative weight loss programme
• Intellectual disability