Chronic condition of one or more joints in which the cartilage wears and the adjacent bone produces a knobbly growth in reaction. The cartilage of the joint is first roughened, then gradually disappears, and this and the bone growth cause deformity of the joints, such as Heber-den’s nodes on the fingers. On examining the joint one should pay attention to abnormal protrusions of bone around the joint, restricted movement and associated pain. Laboratory examination does not usually help directly, but could reveal another problem such as inflammation or a tumour which could have caused the osteoarthrosis. X-rays reveal affected cartilage, bone reaction or joint irritation. Before treatment it is important to exclude other causes of pain in the joints, especially rheumatic conditions. Osteoarthrosis cannot be cured, but the discomfort can often be considerably reduced. In the first place strain on the joint should be reduced by losing weight and regular rest, and possibly the use of a walking stick or improvement of posture. In the second place physiotherapy in the form of massage, warmth or ultrashort-wave therapy may be administered, possibly supplemented with painkillers. Activities which do not strain the joints unduly, such as cycling or swimming, can be an essential part of the treatment.