Diagnosis and arthroscopic removal of an intra-articular epidermoid cyst in the distal interphalangeal joint of a 15-year-old horse

This case report describes the diagnosis and arthroscopic removal of a ruptured epidermoid cyst in a distal interphalangeal (DIP) joint of a horse. The cyst was the cause of chronic moderate lameness and following removal the horse returned to athletic performance. However, 12 months postoperatively the horse was retired due to the recurrence of lameness. Epidermoid cysts have been diagnosed elsewhere in the equine digit but have not been reported intra-articularly to the best of our knowledge.