Radiographic and ultrasonographic appearances of chronic tenosynovitis of the lateral extensor tendon at the right tarsus in an Argentinian polo pony

Abstract

A 19-year-old polo pony presented with mild lameness alongside a lateral protuberance of the right tarsus. Radiographic findings revealed various defects, including an osteochondral lesion of the medial trochlear ridge of the talus, a sclerotic lesion of the tarsometatarsal joint, a radiolucent area on the distal border of the fourth tarsal bone and an enthesophyte at the proximolateral aspect of the metatarsal bone. Ultrasonography demonstrated the interesting finding of synovial sheath thickening of the lateral extensor tendon with synovial fluid accumulation. In addition, the presence of neutrophils and a granular mucinous background, according to cytological analysis of the fluid, indicated inflammation of the synovial sheath of the tendon. All evidence suggested that the pony was likely suffering from degenerative joint disease and chronic tenosynovitis of the lateral extensor tendon at the right tarsus. The imaging analyses benefited the tarsal defect investigation and proper disease management.