Heterotopic ossification is defined as the presence of lamellar bone at locations where bone normally does not exist. The condition must be distinguished from metastatic calcifications, which mainly occur in hypercalcaemia, and dystrophic calcifications in tumours. It is a frequent complication following central nervous system disorders (brain injuries, tumours, encephalitis, spinal cord lesions), multiple injuries, hip surgery and burns. In addition to this acquired form, hereditary causes also exist, such as fibrodysplasia ossificans progressiva, progressive osseous heteroplasia and Albright's hereditary osteodystrophy. Although these conditions are extremely rare, they can provide useful information on the physiopathology of heterotopic ossification, and thus lead to novel and causal treatment modalities. Heterotopic ossification is no trivial complication. A limitation of the range of joint motion may have serious consequences for the daily functioning of people who are already severely incapacitated because of their original lesion. Increased contractures and spasticity, pressure ulcers and increasing pain further compromise the patient's capabilities. Consequently, we feel that attention should be paid to the pathogenesis and particularly the prevention and treatment of this disorder.