Hind End Lameness

Hind End Lameness

A flexion test can help determine the area of lameness.

Photo: Stephanie L. Church, Editor-in-Chief

Q. I have a 4-year-old hunter who has become lame in his hind end. He routinely goes over 2' 6" jumps, but never anything larger. Being only 5'3", I do not think that my problem is the weight I am asking him to carry. There are no obvious problems with his hind end that I can see. What types of tests can I expect to be performed on him to determine his lameness?

A. Hind end lameness affects different breeds and disciplines in various ways. A Thoroughbred, Standardbred, or Quarter Horse is going to be affected differently depending on its use. With any lameness exam, however, a case history of the horse should be compiled. Significant to the case is the age of the horse, the type of work the horse does for a living, the events in which the horse has competed recently. Was there some special event that was associated with the lameness, or did the lameness just covertly become part of what was happening to the horse? Ligament problems or fractures should be investigated if the lameness showed up after an event that might have caused stress to the hind end.

Obtaining clinical signs is next on the list after the horse's history has been organized. In order to get clinical signs, the veterinarian performs a physical exam in which any abnormalities of the limbs are noted and taken into account. Heat, pain, and swelling--the cardinal signs of inflammation--are a part of the physical exam. Once a physical exam has been performed, and any inflammation is noted, then a full-fledged lameness exam might be performed if further examination is necessary to determine a diagnosis.

In a lameness exam, the horse is trotted on a straight, solid surface. He is turned clockwise and counter clockwise on a longe line to see if the lameness changes when the direction is changed. This will help localize the area where the lameness originates. A flexion test also will help determine the area of lameness. The first flexion test performed is on the ankle, with the following flexion test being a hock/stifle flexion, so named because the two parts have to flex together, given the anatomy of the hind limb.

The veterinarian will flex the limb, then have the horse trotted off immediately to see if the flexion test caused or accentuate the lameness. If the hock/stifle flexion created lameness, or increased the lameness exhibited by the horse, then the problem more than likely lies in the hock or stifle. This result of the test is called a "positive" flexion test.

After these steps have been followed, the next item on the lameness exam agenda is a series of diagnostic nerve blocks. Areas of the leg are "blocked" with local anesthesia, given where the lameness was localized in earlier tests. The blocks cause the leg to become numb to pain, revealing which structures are involved in causing the pain and lameness. The lameness should go away when the area where it orginates is "blocked" because the horse will no longer feel pain in that area.

With all of these tests completed, the next item on the list is to X ray the area where the lameness is suspected. The X ray allows the practitioner to look for pathology where the lameness has been localized.

If the diagnostic tests localized the problem to an area that was not a joint (e.g. the horse "blocked out" somewhere in the middle of the cannon area), then it might be a suspensory or tendon problem. In these cases, although X rays still might be used, an ultrasound of the tendons and ligaments in the area could prove more helpful.

After the diagnosis of the lameness has been made, then a treatment can be recommended. Depending on the diagnosis, treatment could consist of therapeutic shoeing, medications, stall rest, or intra-articular therapies.

For a young hunter (two to six years of age), as is the case here, the lower hock joints are less suspicious, but they are always a concern when dealing with hind end lameness. The second most-common item on the list of potential problems would be the feet. Once the lower hock joints and feet are eliminated, the next place to investigate is the possibility of a high suspensory tear. This would be number three on the list because it is a general area of concern, especially with performance horses.

For a hunter older than six years, the lower hock joints should be highly suspicious in any hind end lameness. Even without radiographic changes, treatment of the lower hock joints with intra-articular therapy might be recommended. The reason behind using intra-articular therapy is that even without radiographic change or clinical signs, the lower hock joints are the primary area of concern with older hunters.

As with the navicular bone, we are beginning to question how strong a correlation there is with radiographic change and clinical signs. And those lower hock joints could fit into that category. There might be minimal change, but it still can be the source of the lameness. Sometimes you look for a response to treatment, and in the older horses which have been active hunters for most of their lives, there is a good chance that it is the lower hock joints, and they will respond to treatment.

About the Author

John Peloso, DVM, MS, Dipl. ACVS

John G. Peloso, DVM, MS, Dipl. ACVS, is owner and surgeon of Equine Medical Center of Ocala in Fla.

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