Question:

• I see a lot of horses getting their hocks injected. Some horses get theirs injected every few months. Is this healthy?

Answer:

Distal tarsitis, often referred to as "bone spavin", is the most common cause of clinical lameness associated with the tarsus (or "hock") in horses. Distal tarsitis is an osteoarthritis and periostitis (inflammation) of the distal intertarsal, tarsometatarsal, and occasionally the proximal intertarsal joints. Distal tarsitis is a clinical diagnosis.

In other words, demonstration of pain in distal tarsal joints is diagnostic. Pain is demonstrated upon clinical examination, lameness characteristics, response to Churchill's Hock testing, hock flexion, and response to intra-articular anesthesia. Radiographs are frequently used to assess the presence and severity of distal tarsitis. It is important to note, however, that joint inflammation (arthritis) is invisible on a radiograph (which provides only structural information). Since the tarsus is a low-motion area, radiographic changes and the presence of distal tarsitis do not always correlate.

The low-motion nature of the distal tarsal joints also allows veterinarians to be very aggressive regarding treatment, which usually involves intra-articular (joint) injections. Typically, a combination of steroids and hyaluronan is used. Although the excessive use of steroids can be harmful to joints, the lack of movement within the distal tarsal joints presents little risk in regard to future function and performance. In fact, horses that are refractory to distal tarsal injections may be candidates for chemical fusion, which eliminates the joints altogether and produces soundness.