[Obesity and arthritis of the knee]

More than 45 p. cent of patients with degenerative knee arthritis are obese. The overweight is more marked when the medial tibio-femoral and the lateral femoro-patellar aspects are affected. With the same degree of weight gain, the relationship between obesity and degenerative knee arthritis is more marked in women than in men. The significance of the overweight increases the probability of developing degenerative knee arthritis, increasing its functional severity. The obesity precedes the arthritis, and is not its consequence. It is a mechanical effect by increase of the articular strains. It is unknown how long the obesity must be present in order to be pathogenic for the knee and what functional and anatomical improvement may be expected from a weight loss.