(Perthes disease, pseudocoxalgia) necrosis of the head of the femur (thigh bone) due to interruption of its blood supply (see osteochondritis). Of unknown cause, it occurs most commonly in boys between the ages of 5 and 10 and causes aching and a limp. The head of the femur can collapse and become deformed, resulting in a short leg and restricted hip movement. Affected boys are kept under observation and their activities are restricted; surgery may be required in more severe cases. [A. T. Legg (1874–1939), US surgeon; J. Calvé (1875–1954), French orthopaedist; G. C. Perthes (1869–1927), German surgeon]... legg–calvé–perthes disease