Q. We recently had our 4-year-old gelding X rayed due to months of periodic refusal to canter. What we learned was a shock: His hock had been broken and now has healed with what the veterinarian is calling bone spurs. He believes that the spurs are possibly rubbing against his tendon, causing pain. I have not seen the X ray yet, but the vet described it as being a clean break on the bottom bone of hock.

What is the long-term prognosis for injuries such as these? We have never heard of a horses’ hock being broken without indication of it. Should he be working? Or should we do whatever is comfortable to him, as we have no plans to show him? Should he be on any anti-inflammatory medications or supplements?

Tricia Arseneau, via email

A. Those of you who have owned horses with arthritis might be familiar with the term bone spur. Or perhaps you had a prepurchase examination performed on a horse, only to discover that the horse had spurs in his hock joints.

The actual break in the bone you are describing sounds as if the spur itself might have become slightly detached, or it’s enlarged and appears as if it is detached. This is a typical description for bone spavin, which is defined as osteoarthritis of the lower three hock joints. It usually affects the two lowest hock joints (the tarsometatarsal and the distal intertarsal joints), with the third joint, the proximal intertarsal, rarely affected. An extensor tendon complex overrides the area where bone spurs are most likely to occur in the front of the joint.

Most often this type of growth is associated with arthritis of the joint, although we sometimes see spurs incidentally causing no clinical abnormalities. As joint inflammation and deterioration progress, the body starts to produce excess bone at the edges. Sometimes these spurs act to stabilize a painful joint, either by putting pressure on the joint edges or by eventually fusing the joint (preventing any -motion at all). We diagnose the spurs most accurately with radiographs (X rays) or ultrasonography.

Determining whether the spurs are clinically significant can be tricky. Certainly if there is joint swelling, pain on flexion, and the horse becomes more sound when the joint is blocked, the spurs are likely to be signs of trouble.

Administering a local anesthetic (blocking it) is a definitive way of confirming the presence of pain arising from that joint. It should abolish or at least significantly reduce the lameness. This technique is not absolutely specific, as the distal (lower) pouches of the tarsometatarsal joint are immediately adjacent to the suspensory ligament. This means that anesthetic in the tarsometatarsal joint can occasionally desensitize pain arising from the suspensory ligament, giving the false impression that joint pain has been abolished. Scintigraphy (bone scan) can help the veterinarian differentiate between suspensory origin desmitis (inflammation of the ligament at its attachment to the bone) and bone spavin.

If bone spurs are just found on routine radiographs (such as a prepurchase examination), it is much more difficult to predict their long-term consequences. If we feel the spurs are a sign of trouble, we will likely recommend treating your horse for arthritis, which may involve oral joint supplements, injectable joint therapy, or joint injections, depending on the horse’s age and use.

About the Author

R. Reid Hanson, DVM, Dipl. ACVS

R. Reid Hanson, DVM, Dipl. ACVS, joined the surgical faculty at Auburn University in 1992, and is currently a Professor of Equine Surgery and Lameness. He is the author of over 180 scientific articles, abstracts, presentations, and book chapters related to equine surgery, lameness and critical care. Dr. Hanson is also an award-winning speaker, speaking to international audiences about these important topics. In his free time he enjoys competitive swimming and training. More information on Dr. Hanson can be found at www.vetmed.auburn.edu/faculty.dcs-faculty/hanson.

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