January 2, 2022
morel lavallee lesion MLL cover

MOrel-lavallee lesions


The Morel-Lavallee lesion (MLL) is a somewhat uncommon injury encountered in sports medicine practice and delays can occur. It was first described in 1863 by a French physician and is characterized as a degloving injury [1], but wasn’t credited with the eponym until 1993 [2]. Closed degloving injuries develop as a result of blunt trauma with tangential shear forces that separate the hypodermis from the underlying fascia. The disrupted vascular and lymphatic supply of the injured tissue then fills the created cystic space with blood, lymph, and necrotic fat [3]. Diagnosis of these injuries can be delayed due to its association with trauma and other more obvious injuries. It remains important for sports medicine and orthopedic providers are aware that a delay may have undesirable effects such as infection, pseudocyst formation and cosmetic deformity.

Case Vignette

A 41 year old female presents to your office with a 3 month history of swelling over the right upper arm region. She fell off of a horse about 3 months ago and landed directly on her shoulder. She did have some pain initially along with some ecchymosis. This seemed to resolve but she now has painless swelling. On examination, the skin is soft, fluctuant and hypermobile over the lateral shoulder, but there is no motion restriction. The skin is intact and the rest of her examination is normal. You suspect a closed degloving injury. What is the most common location of these lesions?

A) Knee
B) Shoulder
C) Greater trochanter
D) Lower leg

The etiology of MLLs often occurs during high speed motor vehicle collisions or crush injuries and has been associated with pelvic or acetabular fractures [4]. However, it has become increasingly recognized in contact sports such as football, wrestling and horseback riding [5-6]. Other cases have been associated with decubitus ulcers, after liposuction or mammoplasty and some patients fail to recall any specific event [2].

Image 1: Illustration of Morel-Lavallee lesion.  Adopted from [8].

In general, lesion evolution is divided into four stages. During the first stage, the dermis is separated from the underlying fascia. Next, exsanguination from the lymphatics and vasculature from the injured subdermal plexus produces a fluid collection mixture of blood, lymph, and fatty debris. After this stage, over time, these components are replaced by serosanguinous fluid as the lesion enlarges. If left untreated during the acute stage, local inflammation leads to the fourth stage of pseudocapsule formation and lesion maturation as the body attempts to sequester the fluid-filled space [7].

MLLs occur most frequently over the greater trochanter region along the proximal lateral thigh. This is thought to be due to the large surface area, mobility of the skin and dense capillary network within the soft tissue of the proximal thigh and gluteal region [7]. Vanhegan et al reviewed more than 200 MLLs reported in the literature and noted their presence in the following regions: the greater trochanter/hip (30.4%), thigh (20.1%), pelvis (18.6%), knee (15.7%), gluteal region (6.4%), lumbosacral area (3.4%), abdominal (1.4%) and calf/lower leg (1.4%) [8].

Image 2.  Locations reported for MLLs.  Adopted from [8].

The presentation will likely depend on the extent of the trauma and nature of the injury. The extent and rate of hemolymphatic accumulation within the cavity, as well as the patient’s body habitus, frequently determine the clinical identification of an MLL. Fractures of the proximal femur, pelvis, and acetabulum may occur simultaneously with these soft-tissue degloving injuries [7]. There may be associated bruising in the region and some patients have pain over the injury site with reduced mobility. Others, however, may have no pain associated. The patient may seek help more quickly if there is pain associated and some will delay, hoping the soft tissue collection will resolve spontaneously. Some may wait long enough until some level of skin necrosis occurs.

physical examination

On physical examination, a soft, fluctuant area with hypermobile skin is a typical finding. Ecchymosis, laceration or necrotic changes may be observed in the region, though this may be delayed several days. The size of the lesions are typically noticeable on inspection and normally noticed on palpation. The area over the lesion and surrounding area may be tender to palpation. Motion restriction may be present depending on the location of the lesion. Hudson estimated that as many as one-third of MLLs go undiagnosed at the time of acute trauma. Ideally, the diagnosis is made by physical examination [9].


Many different types of imaging modalities have been used to assist in the diagnosis of MLLs and any concurrent conditions.  These include ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI).  Plain radiography may show a nonspecific soft tissue mass, which may indicate further diagnostic tests or a possible underlying fracture.  Many times plain radiographs are done of the region to rule out any fractures or bony lesions.  CT can also be used in a similar manner and MLL appears as a well-defined, encapsulated fluid collection that occasionally shows fluid levels on CT resulting from sedimentation of cellular blood components[10].

Ultrasound can be utilized effectively to confirm the presence of a suspected MLL. MLLs have a characteristic location anterior to the muscle layer and posterior to the hypodermis, as shown in US. Parra et al described MLL as a well-defined anechoic mass representing a liquefied hematoma [11]. Hyperechoic nodules, corresponding to remnants of fat, may be present in the wall of the mass. A retrospective study conducted by Neal et al. demonstrated that acute and subacute lesions had a heterogeneous appearance with irregular margins whereas chronic lesions tended to be homogeneous with smooth margins. As for the shape of the lesion, fluid collections less than one month old tended to be lobular, and chronic fluid collections that were several months or older were more likely flat or fusiform. All fluid collections were compressible without flow on color Doppler imaging [12].
Image 3: US image showing layers involving MLL.  Adopted from https://radiopaedia.org/cases/morel-lavallee-lesion-10?lang=us

Image 4. US image of chronic MLL. Adopted from [24].

MR imaging is the imaging modality of choice in the assessment of MLL. MRI findings also depend on the time of presentation of the lesion. In the acute phase, blood clots and debris may be found depicting a hyperintense collection on T2-weighted sequence (Fig. 3). With organization of the hematoma, there is conversion of deoxyhemoglobin into methemoglobin. These lesions are iso- to hyperintense on T1-weighted images (Fig. 4). The lesion periphery becomes hypointense on T1- and T2-weighted images in due course because of the presence of hemosiderin. With time, the collection becomes a T2 hyperintense seroma with T1 and T2 hypointense pseudocapsule [13]. Mellado et al. described a classification of MLL based on the MRI findings [14].

Image 5. MRI Axial view of MLL over left trochanter. Adopted from [13].

Image 6.  Mellado classificantion of MLLs.  Adopted from [14].


MLL diagnosed early are probably more amenable for conservative management. In a series of MLL over the knee of NFL football players, 52 % of the lesions resolved with compression bandages, cryotherapy, and motion exercise alone. The rest were treated with at least one aspiration and 11 % of them were successfully treated with doxycycline [15]. Early subjection of patients to MRI revealed such lesions and hence could be treated efficiently. Lesions detected late may occasionally be treated conservatively, but the treatment duration tends to be longer [16]. The fluid in MLL is considered sterile in the absence of obvious signs of infection and growth of bacteria is rare, but has been reported [2].

Flow chart 1.  Algorithm proposed for acute MLLs.  Adopted from [13].

Sclerotherapy seems to be a valuable adjuvant to percutaneous drainage being commonly used as a treatment of malignant pleural effusions. Different sclerosants used include erythromycin, alcohol, bleomycin, tetracycline, doxycycline, and talc [17-18]. They act by causing pleural scarring, thereby preventing fluid recurrent accumulation. The justification of such sclerotherapy was inferred following comparison of MLL with lymphoceles. MLLs share the same histologic characteristic with these lesions since they are all lined by a lining of squamous mesothelial cells and various amounts of fibrous tissue. Timing of sclerotherapy does not seem to influence the outcome. It has been variously used for lesions 3–6 months old or for recurrent MLL [19-20]. Sclerosant injection usually follows percutaneous drainage. The solution is injected into the drained cavity and aspirated after 10 min to 1 h.
Surgical intervention is chosen occasionally in the management of MLL. It is generally guided by the nonresponsiveness to conservative management, unclear diagnosis, or evidence of secondary infection [13]. The skin over a MLL remains intact, and hence, the infection of the cyst is due to bacterial translocation from the central circulation. This is generally a delayed phenomenon and probably more common in a larger lesion. A formal open débridement has been proven to be effective, but this approach compromises the subdermal vascular plexus, the only remaining blood supply to the superficial tissue, potentially endangering this tissue. Carlson et al reported using a standardized formal open approach that emphasized dead space closure to treat 24 symptomatic MLLs and reported no recurrences, no infections, and minor superficial skin loss in two patients [21].
A more limited approach using smaller incisions has shown proven effectiveness. Hudson et al reported using a limited incision over the lesion, copious irrigation, and lesion aspiration, followed by compression bandaging [9]. Tseng and Tornetta11 performed a similar technique in 19 patients who had an MLL with surgical drainage within 3 days of initial injury. In this study, 15 patients had a concurrent pelvic or acetabular fracture. The authors describe using a pair of 2-cm incisions strategically placed over the proximal and distal extent of the lesion. A brush and pulsed irrigation were used to débride necrotic and loculated material and a percutaneous drain was used. The drain was removed after 2 weeks or after output was noted to be <30 mL over 24 hours. All patients in this series healed without complication, demonstrating the safety and efficacy of this novel strategy [22].

Flow chart 2.  Proposed algoritm for chronic MLLs.  Adopted from [13].


In conclusion, Morel-Lavallee lesions are closed soft-tissue degloving injuries that result in the separation of the hypodermis from the underlying fascia and most commonly occur around the hips and pelvis. It is important to identify fractures and have a suspicion for these lesions to prevent poor outcomes or delay in diagnosis. Ultrasound has utility to confirm diagnosis,but MRI is the gold standard for imaging. Treatment of the MLL is based on lesion size, location, and proximity to the site of anticipated surgical procedures. Smaller lesions may be amenable to nonsurgical management or focused aspiration. Large or symptomatic MLLs, especially when located in the proximity of intended surgical incisions, should be addressed with débridement and irrigation through a single incision or multiple incisions to reduce the risk of undesired sequelae. Multiple reports in the literature have detailed approaches for the management of MLLs, but the literature on the topic is limited by the infrequency and heterogeneity of these lesions.

Case Conclusion

Correct answer: C. The vignette is describing a Morel-Lavalee lesion, a closed soft-tissue degloving injury that results in the separation of the hypodermis from the underlying fascia and most commonly occurs around the hips and pelvis. The greater trochanter is the most common region affected, with the thigh and pelvis next most common. Vanhegan et al. reviewed more than 200 MLLs reported in the literature and noted their presence in the following regions: the greater trochanter/hip (30.4%), thigh (20.1%), pelvis (18.6%), knee (15.7%), gluteal region (6.4%), lumbosacral area (3.4%), abdominal (1.4%) and calf/lower leg (1.4%).

Vanhegan IS, Dala-Ali B, Verhelst L, Mallucci P, Haddad FS: The Morel-Lavallée lesion as a rare differential diagnosis for recalcitrant bursitis of the knee: Case report and literature review. Case Rep Orthop 2012;2012:593193.23320230
Scolaro, John A. MD, MA; Chao, Tom MD; Zamorano, David P. MD The Morel-Lavallée Lesion: Diagnosis and Management, Journal of the American Academy of Orthopaedic Surgeons: October 2016 – Volume 24 – Issue 10 – p 667-672 doi: 10.5435/JAAOS-D-15-00181


 1. Morel-Lavallee M (1863) Decollements traumatiques de la peau et des couches sousjacentes. Arch Gen Med 1:20–38, 172–200, 300–332

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