Bone diseases are generally congenital or hereditary, nutritional, or traumatic. Congenital disorders include in utero malformations and atavisms, such as polydactyly or persistent ulnae or fibulae in foals; examples of genetic defects are atlanto-occipital malformations in Arabian horses or certain cases of spinal ataxia, canine hip dysplasia, and abnormal bone formation such as that caused by parathyroid hypoplasia.
Bone defects due to nutrition are caused primarily by imbalances or deficiencies in minerals, particularly the trace minerals such as copper, zinc, and magnesium. Calcium and phosphorus concentrations must also be present in the correct ratio. Osteomalacia represents the classic example of imbalanced or deficient calcium and phosphorus intake. Other nutritional disorders are caused by excessive protein intake of growing animals. Either deficiency or excess intake of certain vitamins, particularly vitamins A and D, may influence growth and development of bone. Aseptic physitis or special osteochondrotic conditions of the physes may be caused by zinc toxicity or copper deficiency.
Traumatic causes of bone disorders represent the vast majority of cases and include fractures, fissures, bone bruises, periosteal reactions as a result of trauma, sequestrum formation, and enthesopathies at the insertion of tendons and ligaments. Lack of weight bearing, lameness, reduced motion, instability, pain, heat, or swelling usually accompany these disorders.