12/22/2019
Great article written by Christa Leste-Lassere explaining those subtle lameness issues involving the sacroiliac joint. While reading this, keep in mind that this "joint" is NOT a ball and socket joint as we are used to seeing. The SI joint is a FLAT "joint" that involves a strong ligament that attaches the sacrum to the wings of the pelvis. Basically, this broad ligament is what holds the pelvis and hind limbs on to the horses body. This ligament also serves as the shock absorber for your horses hind end. This is somewhat similar to the shock absorbers in the front end of the horse which attach the front limbs on to the horses body. It is every equestrians responsibility to maintain their horses shock absorbers and assess them frequently.
"Anatomy of the Sacroiliac Region
The sacroiliac (SI) region is the part of the horse’s back where, just as it sounds, the sacrum and the ilium unite. The ilium is the largest, fan-shaped bone of the pelvis, and the sacrum, which is also considered part of the pelvis, is made up of five fused vertebrae that form one solid unit just before the tail.
Two SI joints connect these bony structures, and a series of ligaments along the central aspect of the joints hold those joints together, explains Rob van Wessum, DVM, MS, Dipl. ACVSMR, Cert Pract KNMvD (Equine), of Equine All-Sports Medicine Center, in Mason, Michigan.
The horse is able to move forward efficiently because of this SI region, which transfers forces from the horse’s hind legs to his back. Unlike most other joints and ligaments in the horse’s body, the SI region is designed more for stability and shock absorption than movement.
What's Going On?
When SI disease hits, it can affect one or several structures within the region, says van Wessum. Ligaments can be torn, stretched, or otherwise damaged, and the bones can show arthritic changes. “In most cases, it’s initially ligament damage that wasn’t originally recognized,” he says. “But when the damage has been there for a long time, it creates arthritis in the joints because they’re not properly supported by the ligaments anymore.”
Scintigraphy (bone scans) and ultrasound might reveal changes in ligament fiber patterns or lesions in the attachments between ligament and bone, he says. Bones can be rough or even show signs of fragmentation or avulsion (when a piece of bone breaks off because of a tendon or ligament’s pull). Ligaments that have been damaged for a long time can become thickened, making them less flexible. “Over time, these kinds of changes can lead to a very crooked horse,” says van Wessum.
The Culprits: Injury and Wear
Sacroiliac disease can appear in any age horse, and it’s often the compounding result of injury plus wear. For instance, “they fall or slip and stretch the ligament,” van Wessum says. “And because they’re not giving very clear lameness, the owner doesn’t recognize it and keeps on working the horse.”
A particularly common concurrent injury is to the top of the hind suspensory ligaments that run down the back of each cannon bone, says Sue Dyson, MA, VetMB, PhD, DEO, FRCVS, head of Clinical Orthopaedics at the Animal Health Trust Centre for Equine Studies, in Newmarket, England.
“Frequently, the way they alter their movement because of the pain in their hind limbs places abnormal stress on the SI joints, and so they get secondary SI joint pain,” she says.
Conformation might also be a primary cause, she adds. Horses that are built “downhill”—with their withers lower than their jumper’s bump (the highest part of the croup)—appear to be more susceptible to SI disease. “I suspect that this is a predisposing factor,” she says, adding that research has yet to confirm this hypothesis.
How we train can contribute to SI disease onset, as well, says Dyson. And the shift in training styles over the years seems to be making the condition more common than it was 30 years ago. “Horses are being worked in a different way today,” she says. “Many more horses are being used for single disciplines. Many are working in arenas and not in a variety of situations. These contribute to wear and tear on the body. A horse that is asked to go constantly in circles is not doing what he was designed to do, and I think it affects them mentally, too.”
Signs of a Problem
So how do you know a horse has SI pain? While only a veterinarian can diagnose it, a few signs should raise red flags.
Lameness, interestingly, is not really one of them. Horses can be lame from SI disease, our sources say. But most of them are not.
Perhaps the most common sign—which is also a sign of many conditions—is reduced performance. “A lot of these horses just don’t want to go forward,” van Wessum says. “Or they’ll be uneven in or have decreased capacity for certain exercises, or they’ll be less symmetrical than before, like in pirouettes or when turning.”
Dyson agrees, adding that while some horses might show “genuine lameness as an actual asymmetry,” it’s more common that “they just lack hind-limb impulsion and engagement.”
They might have difficulty in the canter or particularly the lope, since the slowness of the gait seems to produce added challenges. “Their rhythm changes,” van Wessum says. “They can start with a good three-beat canter but then get offbeat and even look ataxic (uncoordinated) sometimes.” The telltale look of the SI-affected horse is that bunny-hop canter, with the back legs moving almost together.
Conflict behavior can also be a sign, as some horses buck or kick out in reaction to the pain they feel working under saddle, Dyson says.
While a characteristic manifestation of the disease is that clinical signs aren’t always evident until the horse is ridden, Dyson says, the horse might still show some indications of discomfort on the ground.
“A lot of horses can be crabby,” van Wessum says, especially if the disease is affecting the joints, which can produce constant, moderate pain levels. They might also frequently shift their weight in the stall. These horses are also likely to be difficult to stand for the farrier, he adds. “Lifting one leg means standing on the other, so they often become unpleasant at that moment, or even try to kick the farrier,” he says.
Palpating the SI area to test for pain won’t offer many clues, says van Wessum. The diseased structures are deep enough in the back that our pushing around on them with our hands isn’t likely to make the horse react.
Conflicting Diagnoses
Sacroiliac disease is easy to mistake for other problems. Owners and veterinarians often think they’re seeing conditions such as ataxia, hock arthritis, or stifle arthritis, van Wessum says. They’ll sometimes recognize it—accurately—as back pain, but they won’t necessarily find the right location. “Many of the horses referred to our practice have gone through three or four diagnoses already,” he says.
If the diagnosis is inaccurate, so is the treatment. Horses will get massages, acupuncture, shock wave therapy, injections, needle therapy—the list is long—all to essentially the wrong area. “But as long as you don’t have the right diagnosis, none of those things work,” van Wessum says.
On the contrary, these efforts delay the time to an accurate diagnosis, leaving the actual problem untreated—and worsening. "
Leste-Lasserre, C. (2017). Sacroilliac Joint Pain in Horses. The HORSE, article 37575
Photo credit Doris Halstead, "Release the Potential."
