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A hallux abducto valgus deformity, commonly called a bunion, is a deformity characterized by medial deviation of the first metatarsal and lateral deviation of the hallux (big toe), often erroneously described as an enlargement of bone or tissue around the joint at the head of the big toe. There is disagreement among medical professionals about the cause of bunions; some see them as primarily caused by the long-term use of shoes, particularly tight-fitting shoes with pointed toes, while others believe that the problem stems from genetic factors that are exacerbated by shoe use.〔 Bunions occur when pressure is applied to the side of the big toe (hallux) forcing it inwards towards, and sometimes under or over, the other toes (angulation). As pressure is applied, the tissues surrounding the joint may become swollen and tender. In a survey of people from cultures that do not wear shoes, no cases of bunions were found, lending credence to the hypothesis that bunions are caused by ill-fitting shoes. The bump itself is partly due to the swollen bursal sac or an osseous (bony) anomaly on the metatarsophalangeal joint. The larger part of the bump is a normal part of the head of the first metatarsal bone that has tilted sideways to stick out at its top. Bunions develop when the pressure of bearing and shifting one's body weight bears unevenly on the joints and tendons of the foot. This imbalance in pressure makes the big toe joint unstable, eventually molding the parts of the joint into a hard knob that juts out beyond the normal shape of the foot. Experts disagree on whether tight, high-heeled or too-narrow shoes cause bunions or whether footwear simply contributes to bunion development. == Signs and symptoms == The symptoms of bunions include irritated skin around the bunion, pain when walking, joint redness and pain, and possible shift of the big toe toward the other toes. Blisters may form more easily around the site of the bunion as well. Having bunions can also make it more difficult to find shoes that fit properly; bunions may force a person to have to buy a larger size shoe to accommodate the width the bunion creates. When bunion deformity becomes severe enough, the foot can hurt in different places even without the constriction of shoes because it then becomes a mechanical function problem of the forefoot. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bunion」の詳細全文を読む スポンサード リンク
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