Access Keys:
Skip to content (Access Key - 0)

Myositis ossificans


  • Solitary, non-progressive, benign ossifying condition of soft tissues
  • Synonymous with heterotopic ossification
  • Not to be confused with fibrodysplasia (myositis) ossificans progressiva, a rare, inherited fibrosing and ossifying disorder of  multiple soft tissue sites (often upper extremity and back); progressively disabling and fatal  


Athletic adolescent or young adult (second through third decades of life)


  • Enlarging mass in arm or thigh
  • Patient generally has experienced a recent, often low-grade limb trauma
  • Commonly involved muscles include quadriceps, brachialis, and deltoid
  • Patient may present with significant pain 1 to 2 weeks after a  trauma with rapid enlargement of lump
  • Pain often decreases as time goes on, differentiating myositis ossificans from osteosarcoma, in which pain is often unrelenting and progressive

Physical /laboratory findings

  • Swelling, warmth at involved site
  • Lesions typically distant from joints within substance of involved muscles (quadriceps, brachialis, deltoid)
  • Increased ESR and serum alkaline phosphatase levels

Plain films

  • Radiograph taken soon after onset of symptoms may not reveal calcification
  • Within 1-2 weeks, a poorly defined area of peripheral calcification may appear
  • At 2-4 weeks after injury, X-ray shows round mass with distinct margin of mature peripheral calcification; well delineated from surrounding tissue
    • Center of mass more radiolucent, consisting of immature osteoid and primitive mesenchymal tissues; mature calcification will progress toward center of mass
      • In contrast, osteosarcoma calcifies early at its center and continues to periphery, a key distinguishing feature between the two entities  
  • Lesions usually 2-5 cm in diameter

Bone scan

  • At less than 3 weeks post-trauma, bone scan will demonstrate increased uptake in area
  • Also helpful in determining timing for surgical excision: Lesions should be excised only after bone scan demonstrates decreased activity

CT scan

Often helpful in delineating a central radiolucency surrounded by a dense periphery

Differential diagnosis

  • Osteosarcoma
  • Myositis ossificans progressiva

Natural history

Over time, volume of heterotopic bone formation will decrease and soft tissue mass will shrink in size


  • Gross: Shell of bony tissue with soft reddish brown central area; mass may be attached to bone by a stalk, may be in continuum with periosteum or may be solely adherent to surrounding muscle
  • Microscopic: Acutely, undifferentiated mesenchymal cells proliferate and infiltrate the muscle
    • At 2-3 weeks, osteoid production begins with progressively more distinct trabeculae at periphery of the lesion
    • Bone usually immature and woven with large, round, and crowded osteocytes; longstanding lesions, however, may mature to a lamellar pattern along the periphery
    • Center of lesion contains irregular mass of active, immature fibroblastic cells with foci of interstitial microhemorrhages that are rarely extensive 

Diagnosis and treatment

  • Early biopsy of lesion may make it difficult to differentiate a focus of myositis from sarcoma based on histology alone
  • Clinical and radiographic correlates essential, with critical distinction being whether lesion is most mature at its periphery (ie, myositis) or in its central core (ie, osteosarcoma).
  • Treatment generally conservative
  • Early surgery contraindicated
  • Excision an option after decreased activity is evident on bone scan

Recommended reading

Bullough P. Orthopaedic Pathology (fourth edition). 2004 Elsevier Limited  2004.

Beiner JM, Jokl P. Muscle Contusion Injuries: Current Treatment Options. JAAOS 2001  9:227-237

Peer Review

OrthopaedicsOne Peer Review Workflow is an innovative platform that allows the process of peer review to occur right within an OrthopaedicsOne article in an open, transparent and flexible manner. Learn more

Instructions for Authors

Read our Instructions for Authors to learn about contributing or editing articles on OrthopaedicsOne.

Content Partner

Learn about becoming an OrthopaedicsOne Content Partner.

Academic Resources

Resources on Myositis ossificans from Pubget.

The license could not be verified: License Certificate has expired!
Orthopaedic Web Links

Internet resources validated by

The license could not be verified: License Certificate has expired!
Related Content

Resources on Myositis ossificans and related topics in OrthopaedicsOne spaces.

Page: Myositis ossificans (OrthopaedicsOne Articles)
Page: Glomus tumor (OrthopaedicsOne Articles)
Page: Pigmented villonodular synovitis (PVNS) (OrthopaedicsOne Articles)
Page: Synovial sarcoma (OrthopaedicsOne Articles)
Page: Giant cell tumor of tendon sheath (OrthopaedicsOne Articles)
Page: Fibromatosis (OrthopaedicsOne Articles)
Page: Dermatofibrosarcoma protuberans (DFSP) (OrthopaedicsOne Articles)
Page: Angiosarcoma (OrthopaedicsOne Articles)
Page: Desmoplastic fibroma (OrthopaedicsOne Articles)
Page: Epithelioid sarcoma (OrthopaedicsOne Articles)
Showing first 10 of 371 results