Foot problems can commonly cause horses to be scratched from a race, lose training days, overload other structures, and have shortened careers. Functionally adapted for speed and efficient use of energy, the Thoroughbred foot is light and lacks the mass for protection commonly seen in heavier boned breeds.
The relatively thin walls and sole of the Thoroughbred foot make it more susceptible to trauma, injury, and hoof capsule distortion. Hoof capsule distortion refers to misshapen/imbalanced hooves such as flares, cracks, underrun, and collapsed and sheared heels. Distortions affect function and have been correlated with musculoskeletal injuries and lameness. Foot shape and balance are paramount to maintaining soundness and optimal performance. Maintenance and development of a healthy functional foot are necessary for well-being and longevity of racehorses, requiring a proactive approach including balanced shoeing and support.
The heel region is designed to impact the ground first and dissipate vibrations. This is usually the first part of the foot to display distortion since it is made up of soft, elastic structures. The toe is stiffer and designed to cut into the ground for traction. Hoof capsule distortions occur slowly over time and result from long-term abnormal weight bearing.
The most common imbalance encountered is feet shod with too much toe length and inadequate heel length. The center of the shoe’s weight bearing surface should line up with the center of the coffin joint which is aligned at the widest part of the sole. Balanced shoeing around the coffin joint helps to distribute force more appropriately over the hoof.
The foot has the ability to handle large impact forces without structurally collapsing. Most hoof capsule deformities (such as underrun and collapsed heels) develop slowly and result from long periods of constant low level-loading. Racehorses generally spend 22 or more hours a day standing in a straw-bedded stall, and most distortions likely occur while the foot is semi-static. During this period the foot is mostly dependent on its architecture for support.
Horses standing with little arch or sole support slowly fatigue the integrity of the capsule. The arch of the sole slowly flattens, the heel becomes underrun and folded inward, and the heel bulbs can become sheared. The insidious nature of hoof capsule distortions slowly compromise the foot, rendering it more susceptible to acute injury. Providing support to the arch is very important, especially when the horse is standing for long periods. When exercising, the track surface packs into the sole and provides support. When in the stall, the hoof has little arch support and relies on the perimeter hoof capsule for support.
Using temporary arch supports bandaged onto the feet when stalled is often very helpful. These can be taken out when exercising. Other options include stabilizer plates and heart bars which are welded into the shoe. These provide support and protection while exercising, but do add weight to the foot and might affect the horse’s gait.
Various options are available for treating the distorted foot. Detecting a compromised hoof capsule, ensuring it is shod in a balanced manner, and implementing one of the support methods can help maintain or develop a functional sound foot.
CONTACT: Scott E. Morrison, DVM—859/233-0371—firstname.lastname@example.org—Rood and Riddle Equine Hospital, Lexington, Kentucky
This is an excerpt from Equine Disease Quarterly, funded by underwriters at Lloyd's, London, brokers, and their Kentucky agents.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.