Clinics in diagnostic imaging (164). Morel-Lavallée lesion

A 31-year-old male motorcyclist presented with prepatellar swelling of the left knee after a collision with a car. Magnetic resonance imaging of the knee showed no bony or ligamentous injury to the knee. Instead, a well-defined, thin-walled, T2-weighted hyperintense fluid collection with internal septations was identified in a prefascial location overlying the left patella and patellar tendon. The findings were in keeping with those of a Morel-Lavallée lesion, a closed internal degloving injury. Morel-Lavallée lesions are occasionally encountered after a blunt soft-tissue trauma. The presentation and imaging features are discussed.