Sacroiliac Pain in Horses

The sacroiliac joint is located beneath the highest point of a horse’s rump. This junction of the ilium (an upper part of the pelvis) and the sacrum (the section of the spine just in front of the tail) includes bones, cartilage, synovial fluid, and three sets of ligaments. 

Pain in the region of the sacroiliac joint is occasionally diagnosed in Thoroughbred and Standardbred racehorses, hunters, jumpers, and dressage horses. A complete lameness examination should be performed because many horses that are back-sore are protecting some other area causing lameness, such as the hocks.

Use seems to be a more important factor than breed in the occurrence of discomfort, though warmbloods were overrepresented in one study of sacroiliac pain. Taller, older, and heavier horses seem to be at somewhat increased risk, as are those that are not properly conditioned for the work they are being asked to perform.

As the horse flexes and extends the hind legs, forces applied to the sacroiliac joint can cause strains or tears in the ligaments as well as partial dislocation of bones. These injuries cause pain and stiffness. Arthritis, common in older athletic horses and those that have been used in strenuous performance, can also be a cause of sacroiliac pain. Horses with sacroiliac pain will flinch downward, sometimes spectacularly, when pressure is put on the top of the rump. Discomfort may cause hind limb lameness, poor performance, reluctance to move forward, and unwillingness to canter or to pick up a particular canter lead.

Conformational lack of symmetry between the left and right pelvic bones has been cited as a cause of sacroiliac problems, but one study showed that horses with asymmetric halves of the pelvis did not have significantly more pain than horses with better skeletal symmetry.

A visible bump may develop at the high point of the horse’s rump due to sacroiliac strain or injury. Because it is often seen in horses that jump, this is commonly known as a “hunter’s bump” or “jumper’s bump.” This bump can be prominent when an injury is new, though most hunter’s bumps shrink somewhat with time.

Treatment of sacroiliac pain may include rest, steroid injections, and anti-inflammatory medications. Shock wave therapy and acupuncture have been helpful for some horses.

Beginning slowly on a horse’s conditioning program and very gradually increasing the level of performance is good insurance against sacroiliac injuries. Keeping both horse and rider at optimal body weights, not working a horse into serious fatigue, and not overdoing jumping practice, especially on an unfit horse, are also preventive measures.