Radiologic case study. Prepatellar Morel-Lavallée lesion.

Although the Morel-Lavallé lesion was originally described over 150 years ago and is a well known entity about the pelvis and femora, its occurrence in the prepatellar region has only recently been reported. While Tejwani et al asserted that prepatellar MLL and prepatellar bursitis can be readily distinguished clinically, the absence of prepatellar MLL from the literature until recently suggests that it may be under-diagnosed. Magnetic resonance imaging can be a helpful adjunct to the clinical examination in diagnosing MLL, primarily by confirming the precise extent of the fluid beyond the expected anatomic margins of the prepatellar bursa. Because both entities are initially treated in the same manner, MRI might be reserved for collections that fail to resolve following conservative therapy or in cases where the diagnosis is questioned. Serial percutaneous aspiration and sclerodesis should be considered in the management of recalcitrant collections or in the initial management of athletes depending on lesion size and range of motion.