Thirty-seven percent of elbows treated surgically for fractures involving the proximal aspect of the radius and/or ulna developed heterotopic ossification. In twenty percent of elbows, heterotopic ossification was associated with clinically relevant motion deficits. More severe heterotopic ossification was encountered in patients presenting with an associated distal humeral fracture, terrible triad injury, transolecranon fracture-dislocation, or Monteggia fracture-dislocation. Patients with an open injury, instability, severe chest trauma, or delay in definitive surgical treatment had a higher prevalence of heterotopic ossification.