Myositis Ossificans

Aka: Myositis Ossificans, Heterotopic Ossification

1. See Also
   1. Hip Injury
2. Pathophysiology
   1. Nonmalignant, soft tissue ossification (esp. quadriceps Muscles, brachialis Muscle, hip adductor Muscles)
   2. Sports-related Trauma to Muscle (or surgery-induced)
   3. Results in Hematoma that ossifies
      1. Fibroblasts differentiate into Osteoblasts, triggered by inflammation
3. Findings
   1. Presents 2 to 4 weeks after injury
   2. Most commonly affects the quadriceps femoris Muscle, brachialis Muscle and hip adductor Muscles
   3. Similar findings as with Quadriceps Contusion
   4. Prolonged, localized Muscle pain
   5. Affected joint is stiff with reduced range of motion, as are the adjacent joints
4. Differential diagnosis
   1. Osteogenic Sarcoma
5. Imaging
   1. Bedside Ultrasound
      1. Preferred first-line study
   2. XRay
      1. May demonstrate ossifications at 3 to 4 weeks
   3. MRI
      1. Hyperintense mass
      2. T2 may demonstrate calcifications
6. Management
   1. Anticipate a prolonged course of spontaneous resolution
   2. Maintain limb range of motion
   3. NSAIDs
   4. Activity restriction
   5. Consider surgical intervention if lesions persist at 12 months
7. Prevention
   1. Early cold therapy
   2. Acetaminophen is preferred in first few days for pain after injury to decrease bleeding risk
   3. Start gentle, static Stretching after first 48 hours following injury
8. References
   1. Creech (2022) Am Fam Physician 106(2): 195-7 [PubMed]
   2. Walczak (2015) J Am Acad Orthop Surg 23(10): 612-22 [PubMed]