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Understanding Sacroiliac Joint Pain

In this video/blog, we’ll be taking a look at the sacroiliac joint as source of pain.

Background / Info

What is the sacroiliac joint?

The sacroiliac (SI) joint

The sacroiliac (SI) joint is located in the pelvis and connects the iliac hip bone (-iliac) to the sacrum (sacro-), which is found at the base of the spine. It is supported by a strong network of ligaments that provides stability and limits the movement of the pelvis. The complex dynamics between your body’s weight and your body’s attempts to counteract that force is found in this core region. This is consistent with the SI joint’s role in controlling and distributing the forces from the upper body into the legs; acting as a shock absorber for the spine; and supporting the weight of the upper body. 

SI joint Pain

An SI joint irritation may cause patients to experience low back or buttock pain. The SI joint is subject to many different types of forces including shearing,… torsion,… rotation,… and tension. The laxity or looseness of the joint decreases, especially around age 40 or 50 when the joint can naturally fuse. Pregnant women are most vulnerable to pain as the hormonal changes cause joint laxity. Both this decrease and increase in joint laxity are known to increase SI joint irritation. 

ypes of forces including shearing,... torsion,... rotation,... and tension

Inflammation of this joint is called Sacroiliitis. Pain is usually worse after maintaining the same position for any length of time. Diseases that can cause sacroiliitis are psoriatic arthritis, spondylitis and reactive arthritis. 

Most people with sacroiliitis present with low back pain, usually worse on one side than the other, which often radiates into the buttock or upper leg on the affected side. Sacroiliitis is often confused with pain from the joints (facets) in the spine. While a physical examination and some diagnostic injections (lidocaine) around the joint can suggest the source of pain, the definitive diagnosis remains a challenge.  .

Chronic SI joint pain, defined by persisting pain that lasts longer than three months, may be due to the degeneration or irritation of the free nerve endings associated with the SI joint. A change in gait, trauma, post-operative fusions of the lower lumbar spine, laxity in the ligaments and muscles around the joint, obesity, and other inflammatory diseases in the body can also affect the sacroiliac joint.


SI joint problems can be difficult to diagnose because of the proximity of the SI joint to the spine. With the prevalence of back pain and spinal injuries, it’s important to distinguish SI joint pain originating from the SI joint as opposed to the lumbar vertebra. For example, degenerative disc disease in the lumbar vertebrae may be interpreted at the SI joint when the source is actually higher in the lumbar spine. 

The key patterns of referral of pain for patients with SI joint problems include thigh, and the knee. Around 50% of these patients report pain in the back of their thigh. Although there is a lack of clearly defined guidelines when it comes to diagnosing SI joint pain, physicians look for pain patterns and reproduction of the buttock and leg pain by pressing on the joint. An MRI is the preferred diagnostic test for evaluating this problem.  


treatment for SI joint pain includes physical therapy, at-home exercises, and over the counter medication

Conservative treatment for SI joint pain includes physical therapy, at-home exercises, and over the counter medication. Corticosteroid injections and radiofrequency ablative therapies may be offered to the patients, but the long term effectiveness of these treatments remains controversial. In severe cases, a SI joint fusion surgery may been offered,  but again,  effectiveness of this option is unpredictable. An important part of the recovery process is patient education, including good posture, proper lifting technique, stretching, and regular exercise to strengthen the muscles and ligaments around the joint.  Fortunately,  sacroiliitis often is a self limiting, and self curing process.  

Now, you know more about the sacroiliac joint and the resulting pain from this joint. Until next time, this is Dr. Shim.

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Last modified: June 17, 2021

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