Bone Spur Prognosis
By R. Reid Hanson, DVM, Dipl. ACVS • Jun 01, 2016 • Article #33979
Photo: Kevin Thompson/The Horse
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.