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Ringbone is exostosis (bone growth) in the pastern or coffin joint of a horse. In severe cases, the growth can encircle the bones, giving ringbone its name. It has been suggested by some authors that such a colloquial term, whilst commonly used, might be misleading and that it would be better to refer to this condition as osteoarthritis of the inter-phalangeal joints in ungulates (Rogers and Waldron, 1995: 34-35). Ringbone can be classified by its location, with "high ringbone" occurring on the lower part of the large pastern bone or the upper part of the small pastern bone. "Low ringbone" occurs on the lower part of the small pastern bone or the upper part of the coffin bone. High ringbone is easier seen than low ringbone, as low ringbone occurs in the hoof of the horse. However, low ringbone may be seen if it becomes serious, as it creates a bony bump on the coronet of the horse. ==Causes of Ringbone== * Excessive tension on the tendons, ligaments, and joint capsules of the pastern area can strain the periosteum. The body compensates by growing bone at the stresspoint. Strain on the extensor tendon, the superficial digital flexor tendon branches, the collateral ligaments, and the distal sesamoidean ligaments are all common factors. If these tissues are stretched or torn, and the joint is instabilized by the injury, new bone is produced to help to stabilize the joint. * Osteoarthritis (the endstage of degenerative joint disease) of the pastern or coffin joint is a very common cause of articular ringbone. Bone is then produced to try to immobilize the joint and to relieve the chronic inflammation of the joint capsule. This process may take years, and lameness will continue until the joint is completely immobilized. * Trauma to the periosteum can cause bone growth on the pastern bone. However, this is usually not progressive unless nearby soft tissue was also harmed and thus the joint instability was affected. * Poor shoeing and conformation, such as long, sloping pasterns, upright pasterns, long-toes with low heels, pigeon toes, splay foot, or unbalanced feet may predispose the horse to ringbone, as they create uneven stress on the pastern and coffin joint, unequal tension on the soft tissues, or worsen the concussion that is absorbed by the pastern area. 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「ringbone」の詳細全文を読む スポンサード リンク
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