Your horse gallops, jumps, collects, turns and extends his stride with power from his hindquarters. And his sacroiliac (SI) joint?the ?meeting place of his pelvis and spine?is critical at every stride. It transfers the action of his hind legs to his back, translating the push into forward motion.
Given the forces that this joint handles day in and day out, it's not unusual for horses to develop SI pain. The trick is recognizing the problem: SI injuries are notoriously hard to pin down, with subtle and confusing signs, easily mistaken for other physical or even behavioral problems. Even a "hunter's bump," a raised area at the top of the croup that's often thought to reveal SI trouble, isn't a reliable sign. (For a closer look inside the joint, see the box below.)
How can you tell if your horse develops SI pain? And, more to the point, what can you do to help him if he does? For this article, we asked Kevin Haussler, DVM, DC, PhD, of the College of Veterinary Medicine and Biomedical Sciences at Colorado State University, for help in answering those questions.
Who's at Risk?
Any horse can injure his SI joint in a fall or some other accident. The injury may leave the joint less stable than it was originally, so it can become a source of chronic pain. Performance horses may develop SI problems through simple wear and tear?and the more mechanical stress the joint comes under, the greater the risk, Dr. Haussler says. SI problems are fairly common. In one recent survey, these problems accounted for more than half of 124 horses presented for back problems at the University of Minnesota equine clinic.
Show jumping and dressage seem to be especially hard on the joint, according to a study carried out by Sue Dyson, FRCVS, and others at the Center for Equine Studies, Animal Health Trust, Newmarket, United Kingdom. That study analyzed records of 74 horses seen for SI pain at the center. Dressage horses and show jumpers accounted for almost 60 percent of the group. Slightly more than half were warmbloods, suggesting that breed may play a role. And horses with SI pain tended to be taller and heavier than average, another sign that mechanical stress is an important factor.
Under stress, Dr. Haussler says, the joint can be injured in several ways. The SI ligaments can tear, just as ligaments and tendons in a limb can give way under stress. And the joint itself, like the hock or any other joint, can become inflamed. Over time, osteoarthritis develops?cartilage wears away and bone remodels. Thoroughbred racehorses sometimes get pelvic stress fractures directly over the SI joint, and those need to be differentiated from SI joint arthritis.
What You'll See
Sacroiliac Joint: A Closer Look
|The sacroiliac joint is the intersection of sacrum, the section of the spine that underlies the croup, and the ilium, the largest of the bones that make up the pelvis. The sacrum is made up of five vertebrae fused solidly together to form a single unit. The ilium is shaped like a fat T, with a narrow shaft that flares out into a wide, flat crest. In conformation diagrams, the spot known as the point of the hip marks the outer branch of the crest, called the tuber coxae. (The true hip is actually farther down, at the base of the ilium shaft.)
The inner branch (tuber sacrale) ends over the sacrum, at the top of the croup. This is the part of the bone involved in the SI joint. If you viewed a cross-section of the joint (below), the two inner branches (one from the bone on the horse's right side, one from the left) would form an arch, with the sacrum in the cleft between them.
Inside the joint, smooth cartilage covers the working surfaces of the bones. A close-fitting membrane encloses the joint and secretes lubricating fluid. Broad, strong ligaments?the dorsal (upper) and ventral (lower) SI ligaments?lash the bones together tightly. There's very little movement in the SI joint; it's designed for shock absorption and stability, not mobility. It has to be strong to hold up under the force of the horse's movement.
SI problems are hard to spot. The joint has almost no range of motion and is buried under layers of muscle and fat, so you can't really see or feel it. And signs of SI pain are often frustratingly vague. Your first hint of trouble may be a change in your horse's performance or attitude?he's not working at his usual level or seems unwilling to work. He lacks impulsion behind, and his quality of movement isn't what it was. Your farrier may tell you that your horse is difficult to shoe behind.
You may see other signs as well. Some may show up when your horse works on a longe line or in-hand. But ?often signs are worse when your horse is ridden or is asked to canter, because these demands call for more hind-limb ?impulsion and put more stress on the SI. Sometimes the signs are apparent only when your horse is ridden, and sometimes they are felt only from the saddle. Horses with SI problems may not look lame, even to a skilled observer, but they ?often feel worse to a rider.
Besides lack of impulsion and reduced quality of movement, you may notice that your horse
- is reluctant to move forward.
- holds his back rigid.
- tends to throw his rider upward and forward.
- is reluctant to work on the bit.
- has trouble with lateral work, such as shoulder-in and half-pass.
- is stiff and crooked at the canter.
- changes his leading hind leg (swaps off behind) at the canter.
- has trouble with flying lead changes.
- bucks and kicks out.
- refuses jumps.
Working your horse in-hand (on a firm surface), you may also see that he travels with a wide-based gait behind and has trouble with foot placement on circles.
A "hunter's bump" just indicates a prominent bony crest?the tuber sacrale?underneath the muscles at the top of the croup. Prominence on one or both sides may be normal for a particular horse, Dr. Haussler says, but if your horse has pain, muscle spasms and joint stiffness in the SI or pelvic region, then the bump is likely to be significant. It may signal subluxation?a partial displacement of the tuber sacrale.
Asymmetrical muscling in the hindquarters is another red flag?or, perhaps, a red herring. Unfortunately, most signs of SI pain can be produced by other conditions. In fact, SI pain often appears along with other musculoskeletal problems. In Dr. Dyson's study, 25 percent of the horses also had lameness in a front or hind limb, and another 25 percent had arthritis or other problems somewhere in their spines.
The problems are often related, but it can be hard to know what came first. Did a lower-leg lameness cause your horse to change his way of going in a way that stressed his SI? Or did SI pain cause him to alter his gaits in a way that overloaded a limb and caused the lameness? Solving the puzzle is a challenge for your veterinarian.
Determining the Problem
Your horse's performance history and a clinical examination are the starting points for the diagnosis, Dr. Haussler says. Your veterinarian will watch your horse in motion and perform a hands-on exam, checking for asymmetries and for pain in response to manual pressure. Only the top parts of the dorsal (upper) SI ligaments can be felt directly, and signs of pain and swelling here suggest ligament damage. The joint itself and the ventral ligaments are too deep to check this way, but rectal palpation of the SI region may also produce a pain response.
The SI joint can also be blocked with an injection of local anesthesia (in the same way that nerve or joint blocks are done in the limbs). This test can confirm that the SI region is the source of your horse's discomfort, but it doesn't tell ?exactly what's going on.
The joint's deep location makes it difficult to image, but several techniques can help zero in on the nature of the problem:
- A bone scan (nuclear scintigraphy) can reveal osteoarthritis. Your horse is ?injected with a radioactive substance that accumulates in areas of active bone remodeling, and a gamma camera tracks the substance as it moves through his body.
- Ultrasound scans can detect damage to ligaments. Transrectal ultrasound (the technique used for equine pregnancy checks) may reveal irregular SI joint margins?a sign of arthritis?as well as damage to the ventral (lower) SI ligament.
- Ultrasound or radiographs can help identify a displaced tuber sacrale.
Even with these tools, it's sometimes hard to figure out the exact nature of an SI problem. But knowing the cause of your horse's pain will increase the odds of ?successful treatment and make a relapse less likely.
Customize His Treatment
Treatment should be customized to the individual case, Dr. Haussler says. Medication, reduced exercise, physical therapy and alternative therapies may all play a role in the program. Here are three key components:
- Reduce inflammation. This is the first step in treating SI pain. Your veterinarian may prescribe a course of oral phenylbutazone (bute) or another nonsteroidal anti-?inflammatory drug. If arthritis or ligament damage is diagnosed, local injections of corticosteroids can help reduce pain and inflammation. The injections are similar to those used in other inflamed joints, such as the hock.
- Reduce exercise. Limited exercise helps by strengthening the muscles that surround the joint?but too much work will aggravate the injury. Your veterinarian can help determine how much and what type of exercise is best for your horse. The program might call for light work in-hand, on the longe line or in a round pen for several weeks. If your horse is comfortable with that, you might start light riding at the walk and then at the trot. Increase work slowly, ?watching carefully for signs that your horse is uncomfortable or ?unwilling.
- Allow turnout. Stall rest isn't recommended for most SI injuries. In most cases, turnout in a small paddock with good footing is helpful. Avoid deep mud, large rocks, poor footing and steep hills, which may aggravate SI problems.
Arthritis in the SI joint can lead to chronic, low-grade pain. In this case, careful management will help keep your horse comfortable.
- Use a progressive (gradually increasing) exercise program to strengthen and supple his hindquarters. Tailor the length, frequency and intensity of the work to suit your horse, Dr. Haussler says, backing off if your horse seems ?unwilling or if other trouble signs return.
- Use cross-training techniques?for example, alternate flatwork, hacks in the field and cavalletti work?to avoid constant or repetitive stress on the joint.
- Avoid activities that are especially hard on the SI region: jumping, ?galloping, abrupt transitions, tight turns and circles.
- Turn out your horse as much as ?possible. Moving around at liberty will help him maintain flexibility, reducing joint stiffness.
Several alternative therapies may help keep your horse on the road to recovery:
- Acupuncture may be useful for pain control in the SI region.
- Therapeutic exercises can help ?restore impulsion and coordination in the hind limbs. Hind-limb stretching exercises that draw the leg forward (protraction) and backward (retraction) may help relax spastic muscles or contracted connective tissue and restore joint mobility.
- Chiropractic or osteopathic techniques may be helpful in chronic cases to restore normal, pain-free joint mobility.
- Massage may help relax muscle tightness in the croup or upper hind limbs.
The outlook for horses with SI injuries depends on the severity and duration of the problem, Dr. Haussler says. A horse with a mild injury should recover and has a good chance of returning to full work. Horses with more severe cases of osteoarthritis or ligament damage may return to a low level of exercise, but their outlook for returning to high performance isn't so good. As a rule, a horse who responds well to treatment has a better chance of full recovery than one who does not.
Kevin K. Haussler, DVM, DC, PhD, ?focuses on equine spinal and sacroiliac ?disorders at Colorado State University's Gail Holmes Equine Orthopaedic Research Center. A doctor of chiropractic as well as ?veterinary medicine, he is an assistant ?professor of ?clinical sciences at the CSU College of ?Veterinary Medicine and Bio?medical Sciences.
This article originally appeared in the September 2009 issue of Practical Horseman