An Unusual Cause of Knee Pain Identified by Point-of-Care Ultrasound in the Emergency Department

Morel-Lavallée lesions (MLLs) are closed degloving injuries that typically result from shearing forces separating the subcutaneous tissue from the underlying fascia, creating a potential space that becomes filled with blood, lymphatic fluid, and necrotic tissue. These lesions are frequently missed on initial evaluation, especially in the context of blunt injury without obvious shearing trauma. Here, we present the case of a 28-year-old male who sustained trauma to his right thigh and knee while attempting to move a refrigerator. Initially diagnosed with a knee contusion after X-rays showed no fracture, the patient experienced worsening pain and swelling, prompting a visit to our emergency department (ED). Upon evaluation in the ED, the sonographic evaluation revealed a large fluid collection overlying the distal lateral thigh and lateral femoral condyle without any associated intraarticular effusion. Findings were consistent with an MLL, which was managed in the ED with ultrasound-guided drainage and compression therapy. This case highlights the importance of recognizing MLLs in the ED, as these injuries are frequently missed on initial evaluation. Early identification and appropriate management of MLL are crucial to preventing complications such as infection, chronic pain, loss of function, and delayed healing.