Morel-Lavallée lesion on the craniomedial aspect of the stifle in a horse: diagnosis, surgical management and outcome

Abstract

Morel-Lavallée lesions (MLLs) are post-traumatic, closed, degloving injuries observed in humans and cats. Morel-Lavallée lesions have never been reported in horses. An 8-year-old Warmblood gelding used for dressage presented with a large swelling on the craniomedial aspect of the stifle that did not respond to conservative treatment. Ultrasonography revealed a large anechogenic fluid-filled cavity with a well-defined capsule. Standing endoscopic examination revealed separation between the deep crural fascia, vastus medialis muscle and skin. Cytology of the fluid collected demonstrated a lymphocyte-rich transudate. Complete surgical excision of the capsule was performed under general anaesthesia. Histopathology of the capsule identified dense fibrovascular tissue lining with an outer thin zone of adipose connective tissue consistent with a MLL. The horse returned to its former athletic level after nine months. The cosmetic outcome was excellent. Chronic MLLs in horses can be successfully treated by complete surgical excision of the capsule with excellent outcome.