AP and lateral x-rays of the knee showing myositis ossificans

Figure 1: AP and lateral radiographs of the right femur


Myositis ossificans, which in this case is acquired from a traumatic injury. This is identified by the radiopaque mass within the muscle body on the AP and lateral views of the femur representing the calcifications (Figure 2).

AP and lateral x-rays of the knee showing myositis ossificans

Figure 2: AP and lateral radiographs of the right femur. Notice the radiopaque mass in the muscle consistent with a calcification (green arrows).

  • Pearl: Traumatic myositis ossificans occurs when damaged muscle body improperly heals leading to partial ossification of the muscle fibers. Occasionally you can feel a hard mass corresponding to the area of ossification in the soft tissues of the muscle on exam.
  • Pearl: Most commonly occurs in the brachialis, quadriceps femoris, and adductor muscles. [1]

Immediate treatment can be directed at pain control and recommendations for progressive mobility. There is no need for an emergent orthopedics consult in the emergency department.

The patient can be discharged home with instructions for using over-the-counter analgesia (acetaminophen, NSAIDs) and follow-up with either PCP, orthopedics, or sports medicine.

  • Pearl: Physical therapy with passive stretching and range of motion exercises are the mainstay of treatment [1].

The prognosis is generally favorable with most patients recovering with conservative therapy. A small minority will need surgery. This patient will likely return to light activity within 3 months and pre-injury level at around 6 months. [2]

Check out ALiEM’s Paucis Verbis cards to brush up on other can’t miss orthopedic injuries, and SplintER Series or EMrad for more cases. For further reading about myositis ossificans check out WikiSM.


  1. Devilbiss, Zachary DO1; Hess, Matthew MD1; Ho, Garry W.K. MD, FACSM, FAAFP, RMSK, CIC2 Myositis Ossificans in Sport: A Review, Current Sports Medicine Reports: September 2018 – Volume 17 – Issue 9 – p 290-295 doi: 10.1249/JSR.0000000000000515 PMID: 30204632
  2. Simon T, Guillodo Y, Madouas G, Saraux A. Myositis ossificans traumatica (circumscripta) and return to sport: a retrospective series of 19 cases. Joint Bone Spine. 2016; 83:416Y20. PMID: 26934992
  3. Ngai A. Post-traumatic myositis ossificans. In: Roger B, Guermazi A, Skaf A, editors. Muscle Injuries in Sport Athletes. Sports and Traumatology. Springer. New York (NY): 2017.
R. Conner Dixon, MD

R. Conner Dixon, MD

Clinical Instructor
Sports Medicine Fellow
Department of Emergency Medicine
Georgetown University/Medstar Washington Hospital Center
R. Conner Dixon, MD

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Alexander J. Tomesch, MD

Alexander J. Tomesch, MD

Primary Care Sports Medicine Fellow
Department of Orthopedic and Sports Medicine
University of Arizona - Tucson
Alexander J. Tomesch, MD

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