Hoof Angles - their influence on limb breakdown
It has been recognised that hoof balance has a direct influence on the distribution of forces and gait patterns of the lower limbs of galloping and jumping horses.
The structure of the horse's hoof, and the heel then toe landing sequence, is able to absorb limited concussion and repeated loading at the gallop.
A study by Dr. Albert Kane and co-workers at Colorado and Californian universities has linked incorrect hoof angles and poor hoof balance to limb breakdown injuries in Thoroughbred racehorses. These studies found that:
- Lower toe angles and low undercut heels increased the risk of fetlock joint and tendon failure in racing horses. Horses with this type of hoof shape transfer more weight to the rear of the limbs, even when standing. They place more constant weight and loading on the fetlock joint and tendons. Decreasing the difference between toe and heel angles when trimming reduced the risk of this type of limb breakdown.
Facts and Stats
- The tendons on the rear of the front limbs have only a 16% overload capacity at the gallop before tendon strain and failure can develop.
- Hoof size and shape do not directly influence the risk of limb breakdown, but trimming to correct poor hoof symmetry in a horse that has developed to accommodate its hoof shape can increase the risk of subsequent breakdown in racing horses.
- The difference between hoof and toe angles in excess of 10% may increase the risk of suspensory failure in galloping horses.
- Very upright toe and heel angles also increase the risk of fetlock and suspensory failure, where both the toe and hoof angles were more upright than the normal 48-55°. The risk of suspensory failure is increased dramatically, when either the toe or the heel (but not both) had a sharper angle.
- Hoof size does not have a significant influence on the risk of limb failure in galloping horses.
- It is often recommended that the hooves be trimmed to balance so that they are symmetrical on the sides. In fact, trimming to correct poor balance that the horse has become accustomed to relative to its limb conformation can increase the risk of severe limb breakdown. Perhaps leaving the hoof balance as nature has intended, provided the toe and heel angles are trimmed to standard angles will help to reduce the risk of severe limb breakdowns in racing horses.
More research has to be carried out in this area to determine other important aspects of hoof shape and balance that influence breakdown, smoothness of gait and racing.