Those of you who have owned horses with arthritis may 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 its hock joints. If you are curious about the actual appearance and origins of these spurs, read on.
A bone spur forms near the edge of a joint surface. It is a change in the normally smooth edge of the end of the bone. It can range from just a sharp corner to a centimeter or larger boney growth (see diagrams). Most often this type of growth is associated with arthritis of the joint, although we sometimes see spurs incidentally (causing no clinical abnormalities). As inflammation and deterioration of the joint progresses, the body starts to produce excess bone at the edges. Sometimes these spurs act to stabilize a painful joint, either by putting pressure on collateral ligaments (thus giving them a more snug fit to the joint, allowing less movement) or by eventually fusing the joint (preventing any motion at all). We diagnose the spurs most accurately with radiographs or ultrasonography.
Determining whether the spurs are clinically significant or not 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. If they 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 age and use of the horse.