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Conformation Problems Lead to Lameness


Pet Column for the week of February 24, 2003


Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Jennifer Stone
Information Specialist

Conformation-the alignment of the bones and joints-is critical to a horse's performance. Conformation can determine the shape of the foot, how the foot wears over time, and the way the leg moves when the horse walks. Some abnormalities simply reduce the visual appeal of the horse, while others can lead to lameness. Knowing about proper conformation can help horse owners recognize potential problems before lameness occurs.

Dr. Allison Worster Stewart, an equine veterinarian at the University of Illinois Veterinary Teaching Hospital in Urbana, says, "A horse with good conformation has lower legs and feet aligned to distribute weight evenly between the inside and outside of the leg."

On evaluating a horse with good conformation from the front, you should be able to draw a straight line that bisects the upper forelimb, the lower forelimb, and foot in the center. The same is true of the hindlimbs when evaluating the horse from directly behind. In addition, the body length of the horse should be equal to or a little longer than the height of the horse at the level of the withers. The withers and the rump should also be at the same height.

"If the body of the horse meets these criteria, then the horse will bear weight evenly over the entire surface of its feet, which means that the hooves will wear evenly and the horse will be less prone to lameness," says Dr. Stewart.

Balance is an assessment of how forehand, the body, and the hindquarters of the horse fit together. "Horse that are balanced and proportional tend to be better athletes with better weight distribution between the forehand and the hindquarters. "Certain body types can predispose a horse to problems," says Dr. Stewart.

For instance, horses with an extremely short back, may have problems with interference between the forelimbs and the hindlimbs. Horses with an exceptionally long back may be prone to weakness of the back for the same reasons that dachshunds often develop herniated disks.

"Although these abnormalities can cause problems, the biggest conformational problems that can lead to lameness occur from the knee down," notes Dr. Stewart. An angular deformity is a deviation often observed at the level of the joint (knee or fetlock). A fetlock that bows toward the outside ("fetlock varus") or the inside ("fetlock valgus") is considered an angular limb deformity. "The varus deformity is definitely the worse of the two," says Dr. Stewart. "It often leads to uneven weight bearing, which can result in severe osteoarthritis of the fetlock joint."

Rotational deformity causes the feet to be pointed either inward or outward (toed in or toed out). Although this condition is not as severe as an angular limb deformity, it can cause the legs to "wing out" or "wing in" with every step. This kind of movement, also called paddling, can predispose a horse's forelimb to interfere with the opposite hindlimb.

"It is important for the horse owner and veterinarian to be able to differentiate between a rotational and an angular deformity," says Dr. Stewart. "A horse with a rotational deformity will 'wing out' or 'wing in,' with its feet during movement, while a horse with an angular deformity will move its lower limbs in a straight line."

Perhaps the most important conformation is the hoof and pastern angle. Ideally, the angle of the hoof and angle of the pastern should be identical and in alignment. If the angle of the pastern is more upright (steep) than that of the hoof wall, the horse may be predisposed to heel pain and foot lameness. A sloping (low) pastern angle in comparison to the hoof wall can cause strain on the fetlock joint. "Regardless of which abnormality the horse has, owners should know that proper hoof trimming can correct it by aligning the hoof wall with the pastern," says Dr. Stewart.

If you have any questions concerning proper conformation, contact your local equine veterinarian.