brand logo

Am Fam Physician. 2022;106(2):195-196

Author disclosure: No relevant financial relationships.

A 16-year-old patient presented with right thigh pain that began three weeks earlier after he was injured in a lacrosse game. He was involved in a collision, with direct trauma to his right thigh, but was able to complete the game. The pain gradually increased over the next few weeks, and he noticed a new palpable mass within the anterolateral thigh.

On examination, a firm, tender mass was palpated over the lateral quadriceps. The patient had pain on knee flexion, and range of motion was limited to 100 degrees. No overlying skin changes or gross deformities were present. Point-of-care ultrasonography was performed, followed by radiography (Figure 1 and Figure 2).


Based on the patient's history, physical examination, and imaging findings, which one of the following is the most likely diagnosis?

  • A. Ewing sarcoma.

  • B. Femoral stress fracture.

  • C. Myositis ossificans.

  • D. Osteosarcoma.


The answer is C: myositis ossificans. Myositis ossificans, also known as posttraumatic heterotopic ossification, is a nonmalignant ossification of soft tissue structures, usually the quadriceps, brachialis, and adductor muscles.1 The condition commonly occurs in athletes following an injury but may also occur after surgery. Myositis ossificans is believed to result from inflammation-induced differentiation of fibroblasts into osteoblasts.1

Myositis ossificans presents as localized muscle pain that lasts longer than would be expected with a contusion or muscle strain. The condition is associated with decreased range of motion in the adjacent joint and stiffness with motion in the affected joint. Presentation may be delayed because pain and range of motion worsen during osteoblastic transformation about two to four weeks after injury.1,2

Radiography can identify myositis ossificans at three to four weeks.1 Magnetic resonance imaging is considered the diagnostic standard, but ultrasonography is emerging as a preferred modality (Figure 3) because of low cost, ease of use, safety profile, and earlier diagnosis.3 Treatment of myositis ossificans includes cryotherapy and early activity restriction. Clinicians should encourage gentle, static stretching beginning no earlier than 48 hours postinjury.4 Acetaminophen is initially preferred over nonsteroidal anti-inflammatory drugs to avoid bleeding risk. Surgery may be considered if lesions persist beyond six to 12 months.2

Ewing sarcoma is the second most common primary bone tumor in children, typically occurring after 10 years of age. It usually affects the extremities but may involve the axial skeleton. Ewing sarcoma may present as B symptoms with localized pain or swelling.59

Femoral stress fractures are relatively rare but can occur in the femoral neck and are more common in endurance athletes. These fractures often cause pain in the groin or anterior thigh that worsens with motion.10,11

Osteosarcoma is the most common primary bone tumor in children, with typical onset during puberty. It develops in the metaphysis of long bones, such as the distal femur. Presenting symptoms include localized pain and a palpable mass or swelling.57,9

ConditionRadiograph findingsUltrasound findings
Ewing sarcomaLytic lesions, aggressive periosteal reaction; lamellated or “onion skin” appearance, cortical disruption, soft tissue massesUneven disruption of osseous structures; heterogeneous, hypoechoic mass directly adjacent to bone
Stress fractureMetaphyseal sunburst appearance, periosteal liftingEarly: hypoechoic, hypervascular cortical rim with surrounding edema; late: cortical disruption or callus formation
Myositis ossificansEarly: faintcalcification; late: progression to diffuse soft tissue calcificationSuperficial, hyperechoic layer distinct from underlying bone (Figure 3; may be absent in acute phase)
OsteosarcomaMetaphyseal sunburst appearance, periosteal liftingSubperiosteal heterogeneous echogenicity with hyperechoic calcifications perpendicular to bone diaphysis; disorganized hypervascularization in lesion periphery

The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Uniformed Services University of the Health Sciences, the U.S. Army Medical Department, or the U.S. Army and U.S. Air Force at large.

Already a member/subscriber?  Log In


From $145
  • Immediate, unlimited access to all AFP content
  • More than 130 CME credits/year
  • AAFP app access
  • Print delivery available

Issue Access

  • Immediate, unlimited access to this issue's content
  • CME credits
  • AAFP app access
  • Print delivery available
Purchase Access:  Learn More

The editors of AFP welcome submissions for Photo Quiz. Guidelines for preparing and submitting a Photo Quiz manuscript can be found in the Authors' Guide at To be considered for publication, submissions must meet these guidelines. Email submissions to

This series is coordinated by John E. Delzell Jr., MD, MSPH, associate medical editor.

A collection of Photo Quiz published in AFP is available at

Continue Reading

More in AFP

More in Pubmed

Copyright © 2022 by the American Academy of Family Physicians.

This content is owned by the AAFP. A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. This material may not otherwise be downloaded, copied, printed, stored, transmitted or reproduced in any medium, whether now known or later invented, except as authorized in writing by the AAFP.  See permissions for copyright questions and/or permission requests.