Morel-Lavallee Lesion (MLL)

Diagnosis
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  • The Morel-Lavallee lesion (MLL) results from a closed traumatic degloving soft tissue injury that most commonly occurs in the area of the greater trochanter and knee
  • The injury results in separation of the hypodermis from the underlying fascia when a shearing force is applied to the soft tissue, disrupting the perforating vascular and lymphatic structures
  • A mixture of blood, lymph, and fatty debris collects in the potential space, which is replaced by serosanguinous fluid as the lesion enlarges; if left untreated, inflammation can lead to pseudocapsule formation
  • Treatment options include percutaneous drainage with sclerodesis, however, once collections are encapsulated, surgical drainage and resection may be required
  • On MRI, the MLLs may be of variable signal intensity depending on the age and constituents of the fluid collection
  • Fibrinous and hemorrhagic debris appears hypointense on T2-weighted images and fat globules appear as dependently positioned hyperintense areas on T1-weighted images
  • Fluid-fluid levels and septations may be seen
  • When a pseudocapsule forms, the collections become circumscribed
  • Fat globules are a specific feature of an MLL
  • Infection, pseudocyst formation, and cosmetic deformity can result from improper or untimely diagnosis and management
  • Most common location is the hip followed by the knee
  1. Gilbert BC et al. MRI of a Morel-Lavallée Lesion. AJR 2004; 182(5):1347-1348
  2. Vassalou EE et al. Morel-Lavallée Lesions of the Knee: MRI Findings Compared With Cadaveric. AJR 2018; 210(5):234-239
  3. Chew FS. Imaging of Soft Tissue Lesions and Calcifications. In: Musculoskeletal Imaging: The Essentials. Wolter Kluwer; 2001:261-262