The sacroiliac (SI) joints are formed by the connection of the sacrum and the right and left iliac bones. The sacrum is the triangular-shaped bone in the lower portion of the spine, below the lumbar spine. The sacrum is made up of five vertebrae that are fused together and do not move. The iliac bones are the two large bones that make up the pelvis. As a result, the SI joints connect the spine to the pelvis. The sacrum and the iliac bones (ileum) are held together by a collection of strong ligaments. There is relatively little motion at the SI joints. There are normally less than 4 degrees of rotation and 2 mm of translation at these joints. Most of the motion in the area of the pelvis occurs either at the hips or the lumbar spine. These joints do need to support the entire weight of the upper body when we are erect, which places a large amount of stress across them. This can lead to wearing of the cartilage of the SI joints and arthritis.
There are many different terms for sacroiliac joint problems, including SI joint dysfunction, SI joint syndrome, SI joint strain, and SI joint inflammation. Each of these terms refers to a condition that causes pain in the SI joints from a specific cause.
As with most other joints in the body, the SI joints have a cartilage layer covering the bone. The cartilage allows for some movement and acts as a shock absorber between the bones. When this cartilage is damaged or worn away, the bones begin to rub on each other, and degenerative arthritis (osteoarthritis) occurs. This is the most common cause of SI joint dysfunction. Degenerative arthritis occurs commonly in the SI joints, just like other weight-bearing joints of the body.
Another common cause of SI joint dysfunction is pregnancy. During pregnancy, hormones are released in the woman's body that allows ligaments to relax. This prepares the body for childbirth. Relaxation of the ligaments holding the SI joints together allows for increased motion in the joints and can lead to increased stresses and abnormal wear. The additional weight and walking pattern (altered gait) associated with pregnancy also places additional stress on the SI joints.
Any condition that alters the normal walking pattern places increased stress on the SI joints. This could include a leg length discrepancy (one leg longer than the other), or pain in the hip, knee, ankle, or foot. Patients with severe pain in the lower extremity often develop problems with either the lower back (lumbar spine) or SI joints. Usually, if the underlying problem is treated, the associated lumbar spine or SI joint dysfunction will also improve.
There are many disorders that affect the joints of the body that can also cause inflammation in the SI joints. These include gout, rheumatoid arthritis, psoriatic arthritis, reactive arthritis, and ankylosing spondylitis. These are all various forms of arthritis that can affect all joints. Ankylosing spondylitis is an inflammatory arthritis that always affects the SI joints. It can lead to stiffness and severe pain in the SI joints, due to inflammation in the sacroiliac joints (sacroiliitis). As the disease process continues, the SI joints can fuse together and have no range of motion. Once this occurs, there is no further pain associated with the SI joints. Rarely, bacterial infection can involve the sacroiliac joints.
The most common symptom of SI joint dysfunction is sacroiliac joint pain. Patients often experience pain in the lower back or the back of the hips. Pain may also be present in the groin and thighs. In many cases, it can be difficult to determine the exact source of the pain. Your physician can perform specific tests to help isolate the source of the pain. The pain is typically worse with standing and walking and improved when lying down. Inflammation and arthritis in the SI joint can also cause stiffness and a burning sensation in the pelvis.
The first step in diagnosis is typically a thorough history and physical examination by a physician. Certain signs can also help differentiate pain coming from the SI joints, lumbar spine, or hips. There are various tests a physician can perform during the physical examination that can help isolate the source of the pain. By placing the patient's hips and legs in certain positions and applying pressure, the SI joints can be moved or compressed to identify them as a source of pain. Other portions of the examination are to exclude certain possibilities that could mimic sacroiliac disease.
The next step in diagnosis is often plain radiographs (X-rays). The patient may have X-rays of the pelvis, hips, or lumbar spine depending on what the physician finds on the history and physical examination. A computed tomography (CAT or CT) scan may also help in the diagnosis. A CT scan gives a more detailed look at the joint and bones. Both X-rays and CT scans can help identify sacroiliitis. This can appear as sclerosis in the joints. More severe wear in the joints can appear as erosion of the bone around the SI joints. These tests can also look for fusion of the SI joints. A magnetic resonance imaging (MRI) scan can also be helpful. This provides a better evaluation of the soft tissues, including muscles and ligaments. It can also identify subtle fractures that may not be visible on an X-ray. The MRI can identify inflammation in the SI joint by the presence of excessive fluid in the joint. A bone scan can be obtained to help isolate the source of the pain and can be used to identify bony abnormalities. The bone scan can identify areas of increased activity in the bone. This is a nonspecific test and can be positive in cases of arthritis, infection, fracture, or tumors of bone.
A helpful method of diagnosing SI joint dysfunction is by performing an injection that can numb the irritated area, thereby helping to pinpoint the pain source. An anesthetic material (for example, lidocaine [Xylocaine]) can be injected along with a steroid (cortisone) directly into the SI joint. This is usually performed with the aid of an X-ray machine to verify the injection is in the SI joint. The anesthetic and steroid can help relieve the pain from inflammation that is common with SI joint dysfunction. The duration of pain relief is variable, but this is very useful to determine that the SI joint is the source of the pain.
As stated above, injections into the SI joint can provide both diagnosis and treatment. The duration of pain relief from injection can last from one day to much more long term. The injections can be repeated each month up to three each year. Oral antiinflammatory medications (NSAIDs, ibuprofen [Motrin], naproxen [Naprosyn]) are often effective in pain relief as well. These can be taken long term if the patient does not have any other medical problems that prevent them from taking these medications. Oral steroids (prednisone) are used as well for short periods of time occasionally to treat the inflammation.
Physical therapy can be very helpful. Pain in the SI joint is often related to either too much motion or not enough motion in the joint. A physical therapist can teach various stretching or stabilizing exercises that can help reduce the pain. A sacroiliac belt is a device that wraps around the hips to help stabilize the SI joints, which can also help the SI joint pain. Other options to stabilize the SI joints include yoga, manual therapy, and Pilates.
If other treatments fail and pain continues to interfere with normal activities, surgery might be an option. Surgery for SI dysfunction typically involves a fusion of the SI joints. In this surgery, the cartilage covering the surfaces of the SI joints is removed and the bones are held together with plates and screws until they grow together (fuse). This eliminates all motion at the SI joints and typically relieves the pain. This should be considered only if other less invasive treatments have not been successful.
The prognosis of sacroiliac joint dysfunction varies depending on the cause of the dysfunction. When the problem is caused by pregnancy, the prognosis is excellent, as the condition usually improves after pregnancy during the postpartum period. Conditions affecting the sacroiliac joints such as ankylosing spondylitis and psoriatic arthritis are chronic, but excellent treatments are available. These treatments can minimize the SI joint pain and prevent destruction of the joints. Degenerative arthritis affecting the SI joint is also a chronic condition and cannot be reversed, but treatments are generally very effective in improving symptoms.
Unfortunately, SI joint dysfunction is not preventable in some people. For many, it is an unfortunate part of the normal aging process. However, the severity can be reduced through treatment with medication, injections, or physical therapy. Maintaining a healthy body weight and good conditioning can reduce the chances of developing SI joint dysfunction and other forms of arthritis. By reducing the loads on the joints, there is less chance for cartilage damage and subsequent arthritis.