The sacroiliac joint is a flattened joint in the pelvic region that joins the spine to the hind limbs. It is a very important area mechanically and one that may be painful more commonly than historically thought.

I consider horses with SI problems as two general groups. The first of these have obvious injuries to this area that result in severe lameness and pain that can be detected fairly easily. This diagnosis is usually pretty easily made, the horse confined for months, and then slowly returned to work. There is often a pronounced "Hunter Bump" on the affected side of horses and the horses tend to be able to return to work after a rest period, sometimes with a permanent blemish. It's important to know that Hunter Bumps may develop in horses without history of severe injury to this area too.

The second group includes horses that have subtle pain without obvious signs externally. This is the group that is hard to diagnose and treat. There are certain lameness characteristics that are considered suggestive of this condition, but none are consistent. Behavior like kicking out when cantering under saddle, plaiting, traveling close behind, and shuffling hind limb gait are all common observations of horses with pain referable to this area. But none are definitive for this condition. Horses with pain in the SI area often are described as lacking impulsion. Some horses respond to pressure over the area, while others are less responsive.

Horses with asymmetry between the tuber sacrale (hunter bumps) are often not in active SI pain, and horses in SI pain often do not have obvious tuber sacrale asymmetry.

The diagnosis can be made with SI block, performed with a long needle. Improvement following the block is evidence that the pain originates here. Clinical lameness exam, ultrasound, and scintigraphy are also all used and may be more or less helpful in particular cases.