Heel Pain in Horses

Understanding navicular conditions to improve your horse's health

by R. Paul Schwab

Most horse owners have heard the dreaded term "navicular disease." It falls in the category with Strangles and colic as far as terms you hope your veterinarian doesn’t mention when discussing the health and soundness of your horse. But what is navicular disease?

Navicular disease has been used over the years to describe a syndrome of pain and inflammation caused by damage to bone and other soft tissues in a horse's heel, usually related to conformation of the pastern and hoof, use of the horse, and breed. This term is better described as navicular syndrome, and more recently, caudal heel pain. Navicular disease refers to a problem with the navicular bone itself whereas navicular syndrome is a term reserved to describe disease that involves tissues associated with the navicular bone. Caudal heel pain describes pain in the navicular bone, deep digital flexor tendon and other associated soft tissues in the heel of the horse.

Anatomy

The navicular bone is a small bone similar to a kneecap in the sense that it floats between the pastern bone and coffin bone and guides the deep digital flexor tendon across the coffin joint and onto the coffin bone. There are multiple soft tissues involved with the navicular bone, including the ligaments that attach it to the coffin and pastern bones as well as the associated joint capsules and, of course, the deep digital flexor tendon.

Pain in this area of the heel is almost exclusively related to hoof and pastern conformation and/or biomechanics. Exceptions would be traumatic injuries such as puncture wounds, lacerations, etc. Horses with low, under-run heels and long toes and horses with short, upright pasterns are the classic heel pain horses. Quarter Horses are more commonly affected because these conformations are more common to the breed as well as the type of work they do. Cutting, gaming and reining horses use their front ends more than other horses, putting more strain on the heels.

Diagnosis of Caudal Heel Pain

Diagnosis of heel pain, as with any other lameness. is made with a combination of examination, history and diagnostic imaging (radiographs and/or MRI). Riders often complain of the horse not turning to one side properly or that the gait has become "choppy." More severe or chronic cases will stand with one foot pointed out in front. Other horses are just more reluctant to work. Foot testers will usually indicate pain at the front or middle of the frog. To get a more specific diagnosis, your veterinarian may put local anesthetic in the navicular bursa or on the nerves that provide sensation to the back of the hoof. If the horse is sound after this anesthetic, chances are the pain is in the heel.

Radiographs are usually taken to get a better diagnosis of what structures are involved. If available, MRI or CT scanning can greatly improve what your veterinarian can see in the foot. There are multiple tiny ligaments and tendons in this area that can be damaged but not seen with radiographs alone; MRI can provide visualization of these structures.

Treatment

Treatment depends on what structures are involved and what type of conformation has predisposed the horse to the condition. For example, if the horse has under-run heels and a long toe, then the treatment should be directed toward shortening the toe and encouraging heel growth toward the rear, rather than forward. Imagine trying to walk around with flippers on. Your calf and heel gets painful.

Heel elevation with a shoe, pad or boot may be warranted as well. Some horses that have had long term heel pain will have contracted heels from not using that hoof as much as the hoof on other side. When viewed from the back the heels on the affected side are narrow and the hoof itself may be smaller and narrower than the other side. Treatment of these should be directed toward allowing the foot to spread out more and getting better support in the heel.

See the example of utilizing digital radiographs to help with trimming and shoe placement, above (hoof pastern axis was improved by almost 10 degrees). In this case the shoe could even be pulled back and the toe shortened more if the sole allowed. This sole was already too thin to do much more, but the horse improved dramatically just with trimming and shoeing alone.

Anti-inflammatory medications such as phenylbutazone are often needed to reduce the initial pain and inflammation. Depending on what structures are involved (soft tissues, bone, joint, etc.) the horse will probably need a period of rest, often several months if ligaments and tendons are damaged. Some veterinarians may recommend treating the navicular bursa or coffin joint with corticosteroids plus or minus hyaluronic acid.

Often, horses with hoof pain of any kind may benefit from chiropractic therapy because of the secondary compensation problems such as neck and back soreness. Chiropractic may actually improve some of the biomechanical problems that initially led to the heel pain.

Summary

Heel pain is a complex syndrome involving several structures that can be difficult to visualize without advanced diagnostic imaging. Overall, it is a conformational and/or biomechanical problem. It can be very painful and career-ending (horses carry 60% of their weight on the front feet). If the conformational problems can be addressed early on with corrective and therapeutic hoof trimming and/or shoeing, the horse can have a much longer, pain-free life.