Pain and Swelling After Injury – Could it be a Morel-Lavallée Lesion?

When pain and swelling linger long after an injury, it’s easy to assume the tissues just need more time to heal. But sometimes, persistent swelling signals a deeper problem. One lesser-known cause is the Morel-Lavallée lesion (MLL) — a post-traumatic soft tissue condition that can be mistaken for a simple bruise or fluid collection. Recognizing this injury early is important because it can persist, enlarge, or become infected if not properly treated. Understanding how these lesions form and progress helps guide accurate diagnosis and effective care.

What is a Morel-Lavallée Lesion?

 A Morel-Lavallée lesion (MLL) is a closed internal degloving injury caused by high-energy trauma that creates a shearing force between tissue layers. This force separates the subcutaneous tissue from the underlying fascia, forming a potential space where blood, lymph, and serous fluid can accumulate. Over time, this fluid pocket can persist, expand, or become infected, and if left untreated, it may lead to tissue necrosis.

How Common is a Morel-Lavallée Lesion?

 Morel-Lavallée lesions are uncommon but not exceedingly rare. They occur in up to 8% of acetabular fractures. The most frequent site is the proximal lateral thigh, particularly the peritrochanteric region. Other affected areas include the gluteal, lumbosacral, and abdominal regions—areas with more mobile skin that are susceptible to shearing forces.

What Are the Symptoms of a Morel-Lavallée Lesion?

 Morel-Lavallée lesions can be tricky to recognize because their symptoms—such as pain, swelling, and bruising (ecchymosis)—often resemble other post-traumatic conditions like compartment syndrome or hematomas.

These lesions usually appear after significant trauma, such as a motor vehicle accident, fall, or sports injury. A common clue is persistent soft-tissue swelling that doesn’t go away with typical treatment or rest. MLL often feels like a soft, fluid-filled pocket under the skin—similar to a half-filled water balloon. It moves easily beneath the skin and has a distinct edge separating it from the surrounding normal tissue. This presentation is different from lymphedema, which causes a more diffuse, firm, and non-mobile swelling without clear borders. During examination, look for:

• A noticeable swelling or bulging area under the skin
• Fluctuance, meaning a soft, fluid-like movement when the area is pressed
• Unusual mobility of the skin over the swelling (the skin may slide more easily than normal)
• Bruising or discoloration that develops gradually over time
• Numbness or tingling (paresthesia) of the skin above the lesion — a key indicator suggesting disruption of small nerves in the area

How does a Morel-Lavallée Lesion progress?

Understanding the anatomy of the soft tissues helps explain the mechanism of an MLL injury. From superficial to deep, the soft tissue layers include:

• Epidermis
• Dermis
• Subcutaneous fat
• Deep fascia
• Muscle

The MLL forms deep to the subcutaneous fat and superficial to the deep fascia, creating a potential space for fluid accumulation. MLLs are most likely to occur in areas where the skin can move freely over a firm structure—such as the outer thigh, hip, or buttocks. These regions are particularly vulnerable when high-energy trauma causes the layers of tissue to shear apart. The result is a boggy, sometimes tender swelling caused by disruption of the small blood vessels and lymphatic channels.

Over time, the body reacts to this collection of fluid through inflammation and eventually forms a fibrous capsule around it, which can make the lesion chronic or recurrent.  Without intervention, MLLs can progress through four stages: 

Stage 1:  Shearing forces cause separation of the dermis and subcutaneous tissues from the underlying fascia.

Stage 2: Damage to lymphatic and vascular structures leads to leakage of blood and lymph into the newly created space. This fluid becomes serosanguinous as the lesion enlarges.

Stage 3: If untreated, chronic inflammation triggers pseudocapsule formation as the body attempts to wall off the lesion, leading to a mature, encapsulated fluid collection.

Stage 4:  Bacterial colonization may occur, seen in up to 46% of lesions, potentially complicating management and delaying recovery. 

Who Is at Risk for Morel-Lavallee Lesion?

Clinicians should maintain a high level of suspicion for a Morel-Lavallée lesion in anyone with:

• High-energy trauma (e.g., motor vehicle accidents, falls, sports collisions)
• Multiple injuries (polytrauma)
• Persistent soft-tissue swelling despite standard care
• Underlying fractures, especially around the pelvis or femur

Up to one-third of MLLs are missed during initial evaluation—often because the lesion may be only mildly symptomatic or overshadowed by more obvious injuries.  Additional factors that should arrouse suspicion include:

• Localized swelling that feels soft or fluid-filled
• Possible bruising or skin discoloration (which may appear several days later)
• Mild tenderness or discomfort
• Numbness or tingling (paresthesia) over the affected skin due to nerve stretching
• In chronic cases, cosmetic contour deformity or fullness that doesn’t go away

How is a Morel-Lavallée Lesion Diagnosed?

Diagnosing an MLL requires a combination of careful physical examination and imaging. Because it can mimic other conditions such as hematoma, bursitis, or even compartment syndrome, imaging helps confirm the diagnosis and assess the extent of the lesion.  Imaging options include:

•  X-ray (Radiograph): May show soft-tissue swelling; x-ray is useful for checking associated pelvic, acetabular, or femoral fractures
•  CT Scan: Commonly used in high-energy trauma; CT scan helps measure lesion size and evaluate associated injuries. 
• Ultrasound: Quick, accessible, and ideal for bedside use; ultrasound can help identify the hypoechoic (dark) area just above the fascial layer and can guide aspiration or drainage procedures.
• MRI: Best imaging method for defining size, chronicity, and internal structure; MRI typically shows a fluid-filled space between soft tissue layers and can help identify if the lesion is acute or subacute:

How is a Morel-Lavallée lesion Treated?

MLLs ranges from simple, non-surgical approaches to more complex surgical procedures. The choice depends on the size of the lesion, symptoms, and whether infection or recurrence is present. Small lesions often respond to conservative care like compression or aspiration, while larger or persistent lesions may require drainage, debridement, or even surgical removal of the lesion capsule.

Compression Therapy:  

Compression therapy is best for small lesions that are less than 50 cm.  It helps encourage fluid reabsorption and prevent re-accumulation.  Manual lymph drainage is not typically effective, but working with a lymphedema therapist can help you:

• Identify the compression garments or wraps that will work best for you
• Prescribe exercises that will further help your reduction
• Monitor your progress and help you know if other treatment measures are necessary

Many small lesions resolve completely with compression—if the patient is consistent and compliant.

Percutaneous Drainage (Needle Drainage with Small Incision):

 Percutaneous drainage is best for small lesions that are < 50 cm and that don’t respond to compression.  However, it can be less effective than open debridement because dead tissue can’t be fully cleaned out.  The lesion is located using ultrasound, then a small incision is made over it. Fluid is suctioned out, the area is irrigated with saline, and a small drain may be placed to prevent fluid from returning.

Incision Irrigation and Debridement (I&D):

Incision irrigation and debridement is best for large lesions that are > 50 cm, for lesions that lie along a surgical incision for fracture repair, or for those that don’t respond to non-surgical care. An incision made directly over the lesion followed by aggressive cleaning and removal of damaged tissue. A drain is placed and kept in place until drainage is < 20–30 cc/day.  The wound may be closed right away or closed later depending on the size,  tissue condition, and factors that affect the  wound healing process.

Open Debridement with Capsule Resection:

Open debridement with capsule resection is best for chronic MLLs that have formed a fibrous “pseudocyst” capsule.  The fibrous capsule is surgically removed to eliminate persistent fluid buildup.  Open debridement can be a challenging procedure and often requires more than one surgery to fully resolve.

Hope for Healing

Persistent pain and swelling after an injury should never be ignored—especially when symptoms don’t improve with standard care. A Morel-Lavallée lesion, though uncommon, is an important consideration in patients with lingering soft-tissue swelling following trauma. Early recognition and appropriate imaging are key to preventing complications such as infection, chronic fluid collection, or skin breakdown. With timely diagnosis and coordinated care—including compression, drainage, or surgical intervention when needed—most patients can recover fully and avoid long-term problems. Increased awareness among both patients and clinicians can make all the difference in catching this often-overlooked injury early and ensuring the best possible outcome.