Rheumatic symptoms are often associated with obesity. The usual symptom is pain in the knee due to gonarthrosis, of which one of the causes is obesity; there is a correlation between the degree of overweight and the severity of gonarthrosis. It is likely, though not demonstrated, that overweight aggravates the arthrosis of supporting joints. On the other hand, obesity limits the post-menopausal bone loss. The intestinal bypass created to obtain a loss of weight may generate complications, and in particular an inflammatory rheumatism due to proliferation of bacteria in a blind intestinal loop, and osteomalacia caused by disorders of vitamin D absorption sometimes develops. The risk of perioperative complications is increased in obese patients. The mid-term results of hip or knee surgical replacement seem to be good. In the present state of our knowledge, its seems to be rational to convince obese patients complaining of rheumatic illness that they should lose weight.