Morel-Lavallée Lesion (MLL)

First described in 1853 by French physician Maurice Morel-Lavallée, the Morel-Lavallée lesion (MLL) is a rare but clinically significant condition. It is a closed soft-tissue degloving injury caused by traumatic shearing forces that separate the skin and subcutaneous tissue from the underlying fascia. This separation creates a potential space that fills with blood, lymph, necrotic fat, and serous fluid, forming a characteristic collection.

MLL may also be referred to as:

• Post-traumatic soft-tissue cyst
• Morel-Lavallée effusion or seroma
• Post-traumatic extravasation

 

Epidemiology and Etiology

MLL is relatively uncommon, with no clearly defined gender predisposition. While some studies suggest a 2:1 male-to-female ratio, others indicate an equal incidence.

Common Causes:

• Blunt trauma (e.g., motor vehicle accidents, sports injuries, falls)
• Iatrogenic trauma (e.g., liposuction, mammoplasty)

 

Pathophysiology

The lesion results from shearing forces that disrupt perforating blood and lymphatic vessels, separating the skin from the deep fascia. Initially, this space fills with hematoma or seroma, but over time:

1. Blood is resorbed, leaving serosanguinous fluid
2. A fibrous capsule may form
3. Chronic inflammation is triggered
4. Leads to encapsulation and potential for chronicity and infection             

 

Common Sites of Occurrence

• Greater trochanter (>60% of cases)
• Proximal femur
• Buttocks
• Knee
• Lumbar region
• Scapular region

 

Clinical Presentation

• Fluctuant, compressible swelling (hallmark)
• Pain and stiffness
• Cutaneous anaesthesia or hypoaesthesia
• Ecchymosis or skin abrasions
• Delayed presentation (weeks to years post-trauma)
• Skin changes - discoloration, necrosis, desquamation

 

Complications

• Infection - cellulitis, abscess, osteomyelitis
• Chronic pain
• Misdiagnosis as soft-tissue tumor
• Pressure necrosis of underlying structures

 

Diagnosing Morel-Lavallée Lesion

Diagnosis involves a combination of clinical examination and imaging.

Imaging Modalities:

• Ultrasound - detects fluid between subcutaneous tissue and fascia.
• MRI (Gold standard) - provides detailed evaluation of:

         > Fluid type and chronicity

         > Capsule presence

         > Adjacent tissue involvement

• CT Scan - less sensitive, may aid in complex cases

 

Differential Diagnosis

• Soft-tissue sarcoma
• Hematoma
• Seroma
• Fat necrosis
• Abscess
• Bursitis
• Pseudolipoma
• Synovial cyst
• Vascular malformation
• Ganglion cyst
• Necrotizing fasciitis

 

Physiotherapy Management of Morel-Lavallée Lesion

Although physiotherapy does not resolve the lesion itself, it is valuable for:

1. Pain reduction
2. improving range of motion
3. Functional recovery (e.g., gait retraining, strengthening)

Management should be individualized, based on:

• Lesion severity
• Medical/surgical interventions
• Duration of immobility or bed rest

Research shows physiotherapy aids post-surgical recovery and improves independence.

Medical Management

Medical (non-surgical) management is usually considered in the early stages of MLL or for smaller, uncomplicated lesions.

Compression Therapy

It is used both early (acute) and chronic MLL cases. It is less effective over mobile areas (e.g., hip or buttocks), where the lesion can shift and resist pressure.

• Helps reduce swelling
• Encourages fluid reabsorption
• Limits further separation of tissue layers

Sclerotherapy

Sclerosing agent (like doxycycline, tetracycline, or vancomycin)is injected into the lesion, causing irritation of the internal cavity lining. It triggers fibrosis and scarring, collapses the fluid-filled space, reducing recurrence.

Some small Morel-Lavallée lesions may resolve on their own with rest, compression, and avoiding further trauma. However, many persist for months or years, potentially causing chronic pain, capsule formation, or infection. These cases often require surgical intervention.

Surgical Management

Indications:

• Failed conservative care
• Chronic or encapsulated lesions
• Infected lesions
• Ambiguous diagnosis

Options:

• Aspiration
• Sclerotherapy (lesions ≤400 mL):
• Percutaneous drainage ± sclerosing agents
• Open drainage and debridement (especially for open fractures)
• Capsule excision for chronic, recurrent, or large lesions