Introduction The term heterotopic ossification refers to the aberrant forma-tion of mature, lamellar bone in nonosseous tissue. Translated from its Greek (heteros and topos) and Latin (ossificatio) etymologic origins, heterotopic ossification can be literally defined as ‘‘bone formation in other location.’’The first written account of heterotopic ossification describes the treatment of symptomatic lesions. Al-Zahrawi (more commonly known in Western cultures as Albucasis), widely considered the father of surgery, wrote in the year 1000 CE,‘‘This callus often occurs after the healing of a fracture... and sometimes there is limitation of the natural function of the limb... if the callus is stony hard and its removal is urgent, incise the place and cut away the superfluous prominence, or pare it away with a scraper until it is gone; and dress the wound until it heals.’’1 Currently, orthopaedic surgeons faced with treating mature, refractory, symptomatic heterotopic ossification are left with few options other than operative excision. Although it is remarkable that the treatment of heterotopic ossification has scarcely changed in the last millennium, it is generally accepted that prophylaxis against heterotopic ossification is far preferable than the later treatment of symptomatic lesions. As such, the focus of scientific effort in recent years has been directed toward prophylaxis, not treatment. The formation of heterotopic ossification has been observed following total hip arthroplasty, acetabular and elbow fracture surgery, electrocution and burn injuries, and traumatic brain injury or spinal cord injury2. Following most traumatic injuries in the civilian population, the formation of heterotopic ossification is relatively rare in the absence of head injury. Even following traumatic brain injury or spinal cord injury, heterotopic ossification develops in only 20% and 11% of patients, respectively3. Rates of heterotopic ossification formation exceed 50% only in the setting of femoral shaft fractures with concomitant head injury4, although reported rates following acetabular and elbow fractures vary substantially. Numerous combat-related injury and amputation studies from the latter half of the twentieth century make no specific mention of heterotopic ossification, suggesting that it was not a common occurrence in prior conflicts5-8. However, military medical texts from the US Civil War and World War I9, 10 make specific mention of heterotopic ossification as a common problem following amputation, as described by Huntington:‘‘... the stumps became conical sooner or later; short stumps sometimes remained well-rounded, long stumps rarely; but when they remained full it was often due to osteophytes, which in time became troublesome.’’10 Thus, since the birth of both surgery and modern warfare, heterotopic ossification has been recognized as a nameless condition that occurs following trauma. Indeed, in the current conflicts in Iraq and Afghanistan, heterotopic ossification has proven to be a frequent occurrence and a common clinical problem. The goals of the present manuscript are to summarize recent findings and the current state of science with regard to combat-related heterotopic ossification as well as to present the preliminary findings of ongoing studies and future directions.