What could cause a change in an adult horse’s leg conformation?
QUESTION I went to visit a friend and her 8-year-old Quarter Horse, and I noticed the horse was toeing in. I have known this horse since his birth and have pictures of him from over the years. Up to two to three years ago he was slightly toeing out. His legs turned out from the knees. This horse has had soundness issues in the past involving caudal heel pain in the right front and some undiagnosed lameness in the right hind, and he was out of work over the winter because of back issues. When I saw him the other day he was standing base narrow with both feet turning in. My first thought was his farrier must have caused the change, but could soundness issues be to blame?
—Lynn, via e-mail
ANSWER Conformation is a highly judged trait in horses. We evaluate it in the show ring, the sale ring, the foaling pasture—everywhere. Conformation can also be a major determinant of an individual’s athletic ability. For example, a horse with straight, “posty” hind legs may be less able to perform a sliding stop or a rollback turn.
There are many recognized possible conformation faults in the lower forelimbs. The front fetlock and knee (carpus) can have flexural, angular, or rotational deformities. The bones’ growth plates can develop abnormally and lead to angular limb deformities. Once the growth plates are closed (finished growing), there is very little change or correction that can be done—at least in a conservative fashion. Foals very often have some degree of carpal valgus (knock knees) that self-corrects as the chest widens with growth. This is an angular deformity in which the lower leg bends outward (away from the midline) from the carpus.
Many angular and rotational deformities may be irreversible by the time the horse is skeletally mature. This age of maturity varies among breeds, as well as individually. A horse is considered skeletally mature by age 2 or 3 in regard to growth plate closure. However, there is a lesser degree of continued and slow growth through age 4 or 5. This would include very small amounts of bone growth and significant muscle development.
Owners often employ corrective or therapeutic farriery to help treat lower limb deformities in foals and weanlings. As horses age, the potential for this type of correction lessens. Many farriers and veterinarians recognize that trying to correct a deformity via shoeing after growth plates close can lead to pain and lameness. For this reason, a foot should be managed in regard to the conformation after skeletal maturity.
The horse in question has had a noticeable conformation change in a relatively short amount of time. This change has clearly developed after skeletal maturity. Therefore, you can essentially rule out the common causes of growth-related distal limb deformation. A bilateral (affecting both sides) change from “turned out” to “turned in” is uncommon and interesting. A base narrow stance can be a dynamic change and could very well be a response to pain (i.e., possibly on the inside/medial side of each leg). The horse could be shifting weight to the lateral/outside aspect of the joints.
An example of this would be a horse with carpal arthritis, which often develops on the medial aspect of the joint first. In this case, a previous diagnosis of pain related to the caudal heel or navicular region is probably a main key to the answer of this question. Horses with pain relating to this region often protect their heels. They commonly develop a short, choppy gait due to reluctance to extend the stride that naturally would lead to a more aggressive heel strike. We often see heel contraction and reduced hoof size, as well. It would not be surprising that chronic heel pain could lead to a change in conformation due to abnormal forces and leg use by the horse.
Having said this, we certainly cannot rule out an imbalance in trimming and shoeing. At this age, the leg conformation should not change permanently from improper hoof “balance,” but such imbalance can cause the horse to try to compensate for the pain. The hoof may also be trimmed in a manner in which he appears to have a hoof or leg deformity. For example, a flare may not be dressed off completely on one side, leaving the illusion that the foot turns toward the flare.
Further diagnostics should help determine the cause of this horse’s conformation change. I often take radiographs of the foot, fetlock, and even the carpus to determine where angulation or rotation comes from. We should be able to see hoof imbalances in relation to the coffin bone and coffin joint. I have the luxury of taking radiographs before working on the feet and following trimming or shoeing to ensure proper alignment or balance. Although this is not necessary in many cases, I would recommend having your friend’s veterinarian and farrier out to the farm together at the first shoeing session going forward to find the right solution for addressing this problem.