The SI joint is the connection between the sacrum (Sacrum) and the ilium (part of the hip). Technically, it isn’t a real joint in the usual sense of the word, as there is no cartilage or joint fluid present. This means: no cushioning and no lubricant.

Transmitting Forces

S and I, sacrum and ilium, are connected by a ligament. The SI joint connects your horse’s back to its pelvis. The SI transfers forces from the engine, the hind legs, to the torso and the rest of the horse's body. The SI is thus essential for your horse’s movement and is constantly in use. There is significant force exerted on the SI.

Wear and Tear

The SI joint is therefore very important for your horse’s movement; it bears a lot of force, but the bones in the SI lie directly against each other, without cartilage cushions or lubricant like joint fluid. This area is constantly moving and is essentially always under tension. You can probably imagine that injuries and wear in the SI joint are always a potential risk.

Use of SI

The SI joint comes under pressure during collection and jumping, among other activities. Sitting under the rider, bringing the hind legs underneath, and, for example, cantering or pushing off for a jump require a lot of strength. These forces must be absorbed by the SI ligament and by the surrounding ligaments and muscles. With overexertion, the ligament will first become irritated. But if the overexertion continues, the bone of the SI can start to produce new cells. New bone structures that do not belong can then form and cause pain. We call this remodeling, which can lead to arthritis (joint inflammation). Sometimes this occurs on one side of the SI, sometimes on both sides. The arthritis is not always severe, but it can be.

How Do SI Problems Develop?

SI problems can develop from:

• Overexertion from improper training
• Overexertion from heavy dressage exercises and collection
• Overexertion from jumping
• Slipping and falling
• Getting trapped in the stable

Overexertion can cause chronic joint inflammations. This leads to instability and compensation patterns in the horse. The horse will then move differently to relieve painful areas. If this compensation leads to improper movement patterns, new issues and wear can arise, often in the SI joint. Jumping horses and dressage horses have an increased risk of SI problems anyway, as high forces are placed on the SI joint in these disciplines.

Symptoms of SI Problems

If the SI joint is painful, it can lead to various (sometimes vague) complaints. Examples include:

• Difficulty collecting
• Difficulty with lateral bending
• Difficulty or incorrect canter transitions
• Refusal, bucking
• Difficulty extending the hindquarters over the jump
• Kicking out after landing a jump

Your veterinarian or physiotherapist can recognize SI issues through symptoms, possible lameness, and an analysis of the hindquarters’ mobility. However, a real diagnosis can only be made with a special ultrasound. Because the SI joint lies very deep within the horse’s body, this ultrasound can only be done through the horse’s rectum. Moreover, it only shows a small part of the SI joint, namely the lower section. Scintigraphy can provide more information about bone formation and remodeling in the area around the SI. But this technique also doesn’t provide a complete and detailed image. MRI and X-ray are not suitable for visualizing the SI joint.

Approach to SI Problems

SI joint issues are usually treated with a combination of pain relief and training. The acute pain must be managed, but the muscles and ligaments around the SI joint also need to be strengthened. Pain relief is usually administered as close as possible to the inflamed area using a long needle under ultrasound guidance. Afterward, you need to train the horse properly, typically under the guidance of a physiotherapist. Correct movement is crucial to optimize and strengthen all the ligaments and muscles surrounding the SI joint.

Supporting Joint Problems

Does your horse have joint issues? The mineral silicon plays a very important role in the formation of cartilage, joint fluid, bones, collagen, muscles, tendons, and ligaments. Therefore, it is an essential supplement if your horse has joint issues. Hydrolyzed, liquid silicon is well absorbed by horses, though it takes some time to see the effects of this supplement. When a horse has arthritis or other joint inflammations, cannabinoids can be an excellent addition. These plant compounds have anti-inflammatory and pain-relieving effects. If your horse has a rigorous training schedule, a regular herbal regimen to help clear waste products from the joints might also be beneficial. Suitable herbs include turmeric, boswellia, horsetail, black currant, and bamboo.