SCIHeterotopic ossification is abnormal bone that grows where it shouldn't — in the soft tissue around a joint — usually in the first weeks to months after SCI. Caught early it can be slowed; ignored, it can lock up a joint. It's worth recognizing.
What It Is
For reasons not fully understood, the body lays down new bone in the muscle and connective tissue around joints below the injury level. In SCI, about 90% of cases involve the hips, but it also occurs at the knees, elbows, and shoulders. As the bone grows, it stiffens the joint and can eventually limit how far it bends — affecting sitting, transfers, and positioning.
Signs to Watch For
Diagnosis
A bone scan detects HO earliest, before it shows on plain film; X-rays confirm it once the bone matures. A blood test (alkaline phosphatase) may be elevated. Because early HO mimics a clot or infection, imaging is how the cause gets sorted out.
Treatment
- Etidronate (a bisphosphonate) is approved to prevent and slow HO in SCI, and works best when started early (within about 3–6 weeks of onset).
- NSAIDs are sometimes used to reduce inflammation and bone formation.
- Gentle range-of-motion exercise helps preserve the motion you have — but should be done carefully, not forced.
- Surgery to remove the excess bone is the most effective fix for significant HO, usually done once the bone has matured; low-dose radiation after surgery greatly reduces the chance it grows back.
What Nobody Tells You
- Lost range of motion is the tell. If a joint suddenly won't move as far as it did last month, think HO and get it checked — early treatment preserves function.
- It mimics a clot. A warm, swollen leg could be HO or a DVT — both need imaging, so don't guess.
- Timing matters for surgery. Removing the bone too early invites regrowth; your team waits for it to mature, often pairing surgery with radiation.
- Keep moving the joint — gently. Maintaining range of motion within a comfortable limit helps protect transfers and positioning.
Sources & Further Reading
Sources include lived experience and published clinical guidance:
- the MSKTC factsheet library (heterotopic ossification is covered across rehabilitation factsheets) — Model Systems Knowledge Translation Center (MSKTC) (see the factsheet library)
- Today's Care — Christopher & Dana Reeve Foundation
- Spinal Cord Injuries — MedlinePlus (U.S. National Library of Medicine)
SCI.help articles are information, not medical advice. Practice varies by injury level, provider, and institution — always confirm specifics with your own care team.