[Illustration: FIG. 120.--Upper End of Femur in advanced Arthritis Deformans of Hip. The shaft is curved and the head of the bone is at a lower level than the great trochanter.] [Illustration: FIG. 121.--Femur in advanced Arthritis Deformans of Hip and Knee Joints. The upper end of the bone shows the condition of coxa vara; the lower end shows enlargement of the medial condyle and alteration in the axis of the articular surface.] These changes are necessarily associated with restriction of movement, and in advanced cases with striking deformity, which consists in shortening of the limb, usually with eversion and displacement of the trochanter upwards and backwards in relation to Nélaton's line. The _clinical features_ are usually so characteristic that there is little difficulty in diagnosis. Restriction of the movements of abduction and adduction, the presence of cracking and of grating of the articular surfaces, and the aggravation of the pain and stiffness after resting the limb, are characteristic of arthritis deformans. The prominence of sciatic pain may lead to the disease being regarded as sciatica. The greatest difficulty is met with in cases in which the disease occurs as mon-articular affection in adolescents, for the resemblance to tuberculous disease of the hip and to coxa vara may be close. Skiagrams do not always enable one to differentiate between them. _Treatment_ is conducted on the same lines as in other joints. The normal movements are maintained by suitable exercises, and an effort is made to diminish the pressure on the articular surfaces in walking by the use of sticks or crutches. Shortening of the limb may be compensated by raising the sole of the boot. When the X-rays show that the disability is mainly due to new bone locking the head of the femur, such new bone may be removed by operation, _cheilotomy_ (Sampson Handley). Excision of the joint has in some cases yielded satisfactory results; it is indicated in young patients who are otherwise healthy, and who are unable to walk on account of pain and deformity. #Osteo-chondritis Deformans Juvenilis.#--Under this term Perthes describes an affection of the hip in children which differs in many respects from the juvenile form of arthritis deformans. Islands of cartilage appear in the epiphysis of the head of the femur, and the epiphysis itself becomes flattened without involvement of the articular surface or of the acetabulum.