<unk>  of varying severity can be caused by surgery or trauma to the hips and legs. About every third patient who has total hip arthroplasty (joint replacement) or a severe fracture of the long bones of the lower leg will develop<unk> , but is uncommonly symptomatic. Between 50% and 90% of patients who developed<unk>  following a previous hip arthroplasty will develop additional<unk> .<unk>  often develops in patients with traumatic brain or spinal cord injuries, other severe neurologic disorders or severe burns, most commonly around the hips. The mechanism is unknown. This may account for the clinical impression that traumatic brain injuries cause accelerated fracture healing. There are also rare genetic disorders causing<unk>  such as fibrodysplasia ossificans progressiva (FOP), a condition that causes injured bodily tissues to be replaced by<unk>  bone. Characteristically exhibiting in the big toe at birth, it causes the formation of<unk>  bone throughout the body over the course of the sufferer's life, causing chronic pain and eventually leading to the immobilisation and fusion of most of the skeleton by abnormal growths of bone. Another rare genetic disorder causing<unk>  is progressive osseous heteroplasia (POH), is a condition characterized by cutaneous or subcutaneous ossification.
Heterotopic ossification
Intramembranous ossification
Metastatic calcification
Ectopic calcification
Dentin dysplasia
Exostosis
Hypercementosis
Osteophyte