Arthritis deformans is rarely the cause of hallux valgus, but the changes characteristic of that affection are commonly present in the joint of the great toe. In pronounced cases, the base of the first phalanx is displaced on to the lateral aspect of the head of the first metatarsal, the exposed head of which frequently shows fibrillation and wearing away of the cartilage, and is often surrounded by new bone, sometimes amounting to an exostosis. There are also fringes from the synovial membrane that may be caught between the articular surfaces. The distal end of the first metatarsal is displaced medially, broadening the tread of the foot, and in severe cases its shaft is rotated on its long axis, so that its dorsal surface looks medially; the great toe is then similarly rotated (Fig. 157). The flexor and extensor tendons and the sesamoid bones are displaced laterally. The ligaments and other soft parts on the medial side are elongated, while those on the lateral side are contracted. In women, the chief complaint may be of the disfigurement of the boot; in others, of pain and disability resulting from the sensitiveness of the joint and of the enlarged bursa over the head of the first metatarsal. The inflamed bursa, which sometimes communicates with the joint, may suppurate, and the infection may spread to the joint. The _treatment_ varies with the severity of the deformity. In mild cases, a great deal can be done by wearing properly made boots and stockings with a separate compartment for the great toe, or a pad of cotton wool or tent of rubber between the great and second toes. The patient should practise manipulations and exercises of the toes and feet, and putting the foot to the ground properly in walking. In pronounced cases, the pain and tenderness must first be got rid of by rest and soothing applications. At night, the attitude of the toe may be corrected by a moulded splint fixed to the medial aspect of the foot by strips of plaster; the toe is then bandaged to the distal end of the splint. Scholl has devised a prop, made of rubber, to be worn between the great and second toes. If there is flat-foot, this must receive appropriate treatment. In aggravated cases, the deformity can only be corrected by an operation which consists in resecting the head of the metatarsal bone, and the tendon of the long extensor may be detached from its insertion and secured to the medial side of the first phalanx. A bar may be placed across the sole just behind the balls of the toes, and the boot should also comply with the anatomical shape of the foot.