Understanding Sacro-Iliac Disease

There can be a variety of reasons for why a horse can go lame. One of the more serious ones is sacro-iliac disease. Here we discuss everything you need to know about this condition.

What is it?

The part of the horse’s rump commonly referred to as the sacro-iliac joint is actually made up of two major parts – the sacrum, which is part of the spinal column sitting within the ilium, and the ilium itself which is the upper part of the pelvis – and is bonded together by connective tissue. This is called the sacro-iliac region and has to take the force of weight and transfer of movement between the spine and the hind legs. The whole area covers the two sides of the pelvis in perfect symmetry having flat surfaces to the parts of the joint involved in the movement of the rear quarters which are supported by three major sets of ligaments and powerful muscles.

When the bond between the two areas of the sacro-iliac joint become weak or loose this can allow movement between the sacrum and the ilium with accompanying pain and inflammation. There may also be loss or wastage of the gluteal muscle and a consequence of this is the appearance of what is known as a ‘hunter’s bump’, essentially a bony protuberance and a lop-sided, or asymmetrical appearance at the top of the pelvis. This can be clearly seen when standing behind the horse’s tail. And when new bone forms on the bony surfaces of the joint along with a build-up of scar tissue, the union of the two sides of the joint become ever weaker.

Injuries Which Can Cause Sacro-Iliac Disease

Any horse can injure the sacro-iliac joint and it is said that frequent jumpers can be especially vulnerable. The most common injuries can occur either through direct trauma to the sacro-iliac region for instance from a fall which results in a sprain or fracture of the bone, or as an indirect injury and pain resulting from lameness in the hind leg.

What Are The Signs of Sacro-Iliac Disease?

In the initial stages, there can be few obvious signs. One of the first and most prominent is the ‘hunter’s bump’ as mentioned earlier, where there is obvious asymmetry in the hind quarters due to a bony protuberance at the top of the pelvis or an imbalance in the size of the gluteal muscles. One of the ways you can check for the condition if you are unable to see any obvious signs is by pressing on the back or pelvis and feeling for any tension in the horse’s muscles, a sure sign of pain.

The most obvious signs will show when you ride the horse. There may be a feeling of disconnection of the stride; it may feel like the horse is powering mostly from the front legs rather than the hind legs. This is commonly due to the shortening of the rear leg stride and often results in a sort of ‘bunny hop’ gait. This may often be the only sign other than a lameness in one leg resulting from a trauma of some kind. Lameness can become worse following flexion of one or both hind legs.

Diagnosis of Sacro-Iliac Disease

This can be complicated because of the need to investigate other possible causes of lameness or altered gait in order to narrow down the options and formulate a treatment plan. Your vet will probably want to carry out a visual evaluation of the horse’s motion as well as a physical examination. Sometimes it is possible to administer a nerve-blocker to the sacro-iliac area to see if there is any improvement in the gait. Howev,er this can be problematic because of the proximity of the sciatic nerve. When this nerve is affected by a blocker the result can be an inability to bear weight on one or both legs at least until the nerve blocker has worn off.

Because of the structure of the musculature of the region, x-rays are ineffective but ultrasound examination could be useful to examine the ligaments and joint contour. This can be performed either externally or internally through the rectum. Ultrasound is not always effective in getting an accurate diagnosis though. By far the most effective way is through nuclear scintigraphy, or bone scanning. This is the most reliable method of identifying asymmetry and inflammation of the sacro-iliac joint structures and will highlight any hot spots which could indicate injury to the ligaments.

What Are The Treatment Options?

It has to be said from the start that there is no quick fix for the problem. Treatment which allows the re-bonding of the two parts of the sacro-iliac joint can take many months and will involve a multi-agency effort. Where there is additional secondary pain, from lameness in the lower leg, hock arthritis or suspensory ligament injury, for instance, this must be treated and managed also. Damage and instability of the sacro-iliac joint may initially benefit from a period of rest, perhaps in the region of 30-60 days in order to reduce the pain of ligament damage.

Obviously, during the treatment and recovery period, it is essential that the horse is not ridden but gentle exercise involving lunging, possibly using stretch bands, long-reining and in-hand work is important for the horse’s mental well-being as much as for the physical benefit. You should still aim to turn out the horse where possible to allow him to move around freely but your vet will advise on whether this is right for your horse. Further exercise will come through working with a suitably qualified equine physiotherapist who can devise a series of stretches, reversing movements and pole work. Hydrotherapy exercises or the use of leg weights to encourage the correct picking up of the feet can be useful aids to muscle building. These are vital to maintaining flexibility and strength in the core muscles during the healing period. The point of exercise therapy is to re-establish the symmetrical muscle development of the back alongside the healing of the sacro-iliac joint region. At all stages of the recovery, it is important to work within the parameters of the horse’s pain tolerance.

Veterinary treatment can include cortico-steroid injections into the sacro-iliac joint to provide pain relief along with anti-inflammatory medications which can be given with food; both are designed to help reduce inflammation as well as help relieve pain. This can be of particular help to horses which struggle to use the hind quarters sufficiently to build up muscle development. Shockwave therapy can also help with pain relief and the promotion of new blood vessels into the damaged areas. All medication and other veterinary treatments must be used in cooperation with strengthening exercises to have the best chance of long-term recovery.

What is The Prognosis?

The chance of a full recovery depends on whether there is an underlying cause for the disease such as injury. If there is only a mild form of the disease the horse should recover well but severe cases will limit the outlook for a full recovery. There is no guarantee of a full recovery from sacro-iliac disease and even if there is no underlying cause only around 50% of horses will be lucky. In general, if the horse responds well to treatment he should have a better prognosis than one which doesn’t.

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