A bunion is a bunion with a lateral deviation of the toe greater than 10° to 15°. It can be combined with a lateral subluxation of the base of the proximal phalanx of the bunion, a bulging of the medial head of the 1st metatarsal bone to form a bony redundancy, a callus formed by friction between the skin and the shoe surface, a bunion formed between the subcutaneous tissue and the joint capsule, and repeated frictional irritation to form a bunion (21-1). The 1st phalanx is internally rotated i.e. the angle between the 1st and 2nd metatarsals is greater than 9°. If the bunion is severe and the bunion angle is greater than 30° to 35°, bunion rotation forward may occur, which is accompanied by outward displacement of the seed bone. The bunion extensor muscle slips to the metatarsal side and loses its strength against the bunion. The lateral heads of the long bunion tendon, long bunion flexor tendon, and short bunion flexor tendon show bowstring-like tension. The force of the bunion is strengthened. The occurrence of bunions may be importantly related to the wearing of inappropriate shoes. In addition, flat feet with uncoordinated 1st metatarsal relationships, such as a rounded 1st metatarsal head and a too long or too short 1st metatarsal. The posterior tibial tendon stop variation, some fibers extend to the oblique head of the bunion and the peroneal part of the thumb flexor, thus increasing the contraction force of the joint tendon of the posterior biceps, and the abnormal bone protrusion between the bases of the 1st and 2nd metatarsals play a role in the development of bunion. Rheumatoid arthritis and neuromuscular disease can also be associated with bunions, and there is a familial tendency for bunions to develop in adolescents. Bunions are most often seen in middle-aged and older women. Patients with bunions do not always have pain, and the deformity is not proportional to the pain. Treatment of bunions is rarely due to aesthetic reasons. The main concern is to relieve the pain. The main cause of pain is acute bunion due to pressure and friction after the medial bulge of the bunion metatarsal head. Long-term abnormalities of the bunion joint, osteoarthritis causing pain and callus under the 2nd to 3rd metatarsal head cause pain. A front and side x-ray of the affected foot in a weight-bearing position is taken and the angle between the median axis of the 1st metatarsal stem and the median axis of the proximal phalanx is measured. The angle between the medial axis of the 1st and 2nd metatarsal trunks is called the angle of the 1st and 2nd metatarsal bones, which is usually less than 9° in normal people. In addition, the x-ray can also reveal the presence of osteoarthritis such as narrowing of the 1st metatarsophalangeal joint, unevenness of the joint surface, and formation of bone redundancy. Patients with mild symptoms can wear loose shoes, and bunions can be treated with physical therapy and hot compresses. Those with severe symptoms need surgery. There are various surgical methods, but no single surgical method is suitable for all bunion patients. The appropriate surgical method should be chosen according to the patient’s specific situation. In mild to moderate bunions, if the angle between the 1st and 2nd metatarsal bones is less than 15°, the medial phalanx of the metatarsal head can be removed and the bunion tendon can be cut or excised. The severed end of the thumb retractor tendon is displaced to the lateral side of the metatarsal head and neck or the metatarsal head and neck is osteotomized and displaced. If the angle between the 1st and 2nd metatarsal bones is greater than 15°, the 1st metatarsal trunk or basal osteotomy is usually used more often. For patients with existing osteoarthritis in the 1st metatarsophalangeal joint, arthroscopic debridement of the 1st metatarsophalangeal joint is more commonly performed in younger patients, while in older patients, fusion of the metatarsophalangeal joint or artificial joint replacement may be used.