Photo Quiz

Knee Bruising and Swelling in a Teenager


Am Fam Physician. 2020 Jul 1;102(1):49-50.

A 17-year-old baseball player presented with pain, bruising, and swelling in his knee 10 days after he injured his left upper leg by dragging his knee and anterior thigh while sliding into home plate. He was able to continue playing after the injury but later developed knee swelling with increasing firmness in the area. He also reported subjective weakness in his quadriceps.

Ice, compression, and ibuprofen provided some relief. He had no history of knee locking, clicking, catching, or instability and had no numbness or tingling. He did not have a previous injury.

Physical examination revealed swelling over the distal quadriceps tendon and bruising along the anterior and medial aspect of the knee (Figure 1). There was tenderness on palpation over the quadriceps tendon and its insertion into the patella. Quadriceps strength was 5/5 with flexion and extension, although he reported some discomfort with flexion beyond 100 degrees. Radiographic findings were normal. Point-of-care ultrasonography was performed (Figure 2).






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

A. Morel-Lavallée lesion.

B. Prepatellar bursitis.

C. Quadriceps tendon tear.

D. Septic arthritis.


The answer is A: Morel-Lavallée lesion. These lesions are closed degloving injuries in which the subcutaneous tissue separates from the underlying musculature, creating a space that fills with blood, necrotic fat, and lymphatic fluid.1 A peripheral fibrous capsule eventually develops around the lesion, causing firmness on palpation.1,2

A shearing force is the usual mechanism of injury. Hours after initial injury, patients typically develop swelling, tenderness, and bruising that can persist for months unless appropriately treated. Delayed diagnosis can increase complications such as necrosis, infection, and disfigurement.2 Definitive diagnosis of a Morel-Lavallée lesion is made with magnetic resonance imaging2; however, point-of-care ultrasonography is increasingly being used to aid in the diagnosis and to quantify the fluid collection.

This patient's ultrasound findings (Figure 2) showed a heterogenous fluid

Address correspondence to Megan Ferderber, MD, CAQSM, at Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.


show all references

1. Scolaro JA, Chao T, Zamorano DP. The Morel-Lavallée lesion. J Am Acad Orthop Surg. 2016;24(10):667–672....

2. Bonilla-Yoon I, Masih S, Patel DB, et al. The Morel-Lavallée lesion: pathophysiology, clinical presentation, imaging features, and treatment options. Emerg Radiol. 2013;21(1):35–43.

3. Nickerson TP, Zielinski MD, Jenkins DH, et al. The Mayo Clinic experience with Morel-Lavallée lesions: establishment of a practice management guideline. J Trauma Acute Care Surg. 2014;76(2):493–497.

4. Tejwani SG, Cohen SB, Bradley JP. Management of Morel-Lavallee lesion of the knee: twenty-seven cases in the National Football League. Am J Sports Med. 2007;35(7):1162–1167.

5. Khodaee M. Common superficial bursitis. Am Fam Physician. 2017;95(4):224–231. Accessed May 15, 2020.

6. Nori S. Quadriceps tendon rupture. J Family Med Prim Care. 2018;7(1):257–260.

7. Caksen H, Oztürk MK, Uzüm K, et al. Septic arthritis in childhood. Pediatr Int. 2000;42(5):534–540.

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

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