Define heterotopic ossification.

• A. The loss of bone mass in abnormal locations
• B. Scar tissue formation in soft tissues
• C. Fluid accumulation in joints
• D. The formation of bone in abnormal locations, often after severe neurologic injuries

Answer: (D)

Heterotopic ossification is bone forming in soft tissues where bone doesn’t normally develop, typically after trauma or severe neurologic injury. The statement that best defines it describes the formation of bone in abnormal locations, often following severe neurologic injuries. This distinguishes it from osteoporosis (loss of bone mass in unusual places), scar tissue in soft tissues, or fluid buildup in joints, none of which involve ectopic bone formation. In practice, HO often occurs around large joints after spinal cord injury or traumatic brain injury, and it can limit range of motion as the ectopic bone matures.