Clinical history A 19 year old Russian warmblood gelding had a long history of right hindlimb lameness treated conservatively for the past 3 years, for the past 3 weeks, the lameness was more acute than before and diagnostic techniques included a series of nerve blocks. Radiographs were made of the metatarsophalangeal joint. The studies were made with the horse being non-weightbearing. Radiographic study of the foot on day 1Radiographic diagnosis The bones and joints were thought to be normal, especially considering the age of the horse. Soft tissue swelling is marked. Radiographic study of the foot on day 13Radiographic diagnosis Uneven collapse of the metatarsophalangeal joint space more prominent medially. Lucency of the proximal subchondral bone in P1 medially. Enlarged radiographs d1 and d13 (arrows)Enlarged radiographs d1 and d13 with changes in contrast (arrows) giovedì 1 ottobre 2009Radiographic diagnosis The second study shows a bone lysis in the subchondral bone in proximal P1 (arrows) with narrowing of the joint space. The radiographic changes are typical for an infectious arthritis with an adjacent osteomyelitis. Comments A joint tap at the time of the first study produced 90,000 cells. A number of attempted nerve blocks had been performed around the joint during the previous days. No radiographic changes were thought present on the first study. The changes on the second study consisted of marked lysis in the subchondral bone and collapse of the joint space. The changes in infectious arthritis are not seen on the radiograph in the acute stages of the disease but are evident 13 days later following cartilage and subchondral bone destruction.
