A 16-year-old male academy player was tackled during a game and sustained a direct blow to the anterior aspect of their left knee. At the time, there was minor discomfort and minimal swelling. This settled completely within 48 hours with rest and icing and the player completed a game 10 days later with no issues. Ten days after this, following a routine training session, the player noticed a recurrence of the swelling, this time much larger than before. There was no pain or stiffness and no locking or giving way. The player was able to complete daily activities and even train without issues. He had no fever or malaise and no inflammatory features.
An MRI of the left knee was performed to further evaluate the injury. This showed a 15 x 2 x 15 cm thin walled fluid collection in the anterior knee, at the junction between the subcutaneous fat layer and the deep fascia. The fluid collection was predominantly of T2 high signal indicating fluid but there was a fluid-fluid level suggesting a haemorrhagic component. The lesion had no significant low signal rim to suggest a fibrous pseudocapsule. There was minor adjacent subcutaneous oedema. There was no bony injury and no other knee abnormality. In the context of the previous direct blow, the appearances were consistent with a Morel-Lavalée lesion.
Given the patient’s age, the relatively small size of the lesion and the absence of a fibrous pseudocapsule on MRI, this patient was managed conservatively with a Game Ready compression unit for 14 days before returning to play. He played using Coban taping to the knee and has not yet had a recurrence of swelling.
Morel-Lavalée lesions are due to post-traumatic separation of the subcutaneous skin and fat from the fascia. The fluid can accumulate slowly over time and a delayed presentation of swelling is not uncommon, sometimes occurring months to year after the injury. There is no accepted treatment algorithm for Morel-Lavalée lesions. Small lesions can be managed conservatively with compression dressings. Larger lesions can be aspirated percutaneously with the caveat that recurrence is not uncommon. The presence of a fibrous pseudocapsule on MRI makes recurrence more likely and, in this situation, aspiration and injection of a sclerosing agent (such as doxycycline or sucrose) or surgical debridement should be considered.
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