A comparison of ultrasound and magnetic resonance imaging findings of a Morel-Lavallée lesion of the knee.

A Morel-Lavallée lesion (MLL) is a posttraumatic soft-tissue injury characterized by an accumulation of blood, lymph, and other physiologic breakdown products between subcutaneous tissue and underlying fascia. It was first described as occurring over the proximal lateral thigh, but it has since been documented at various anatomic locations. Diagnosis is typically made by careful physical examination and a radiographic analysis, most commonly with magnetic resonance imaging (MRI). Recently, musculoskeletal ultrasound (US) has been recognized as a useful adjunct to and potential replacement for MRI in the diagnosis and monitoring of an MLL. We present a case report of a patient with an MLL of the knee. We obtained magenetic resonance (MRI) and US images at the time of diagnosis, and follow-up US images during convalescence. By doing so, we were able to identify several key sonographic findings of an MLL at this location and compare them with MRI. Although there have been several published reports to date that describe the use of musculoskeletal US in the diagnosis of MLL, this is the first of which we are aware that does so at the knee.