What is the SI joint?
Sacroiliac joint (SI joint) is formed by the connection of the two bones in the pelvis, the sacrum and ilium. The sacrum is the triangle-shaped bone near the bottom of your spine just above your tailbone. The ilium, one of the three bones that make up your hip bone, is the uppermost point of your pelvis. The SI joint provides support and stability, distributing your weight across your pelvis. It also acts as a shock absorber by absorbing the impact of walking and lifting.
What causes SI joint pain?
Inflammation of one or both SI joints is called sacroiliac joint dysfunction, or sacroiliitis. Sacroiliitis may be caused by SI joint dysfunction. This is a general term that may be caused by:
- Osteoarthritis: as we age, the cartilage or cushion between our SI joints starts to break down. As with any other joint (such as your knee or hip), this leads to arthritis in the SI joint which can cause pain.
- Too much movement around the joint: if it is hypermobile or unstable, it may generate pain that is felt in the lower back or in the hip
- Too little movement around the joint; if it does not allow movement, it causes stiffness, which causes low back pain
- Pregnancy or recent childbirth: women undergo physiologic and hormonal changes during childbirth. For example, they release hormones that cause their ligaments to be looser to allow more room for the baby to grow. This loosening may cause pain. Weight gain during pregnancy may also cause low back pain.
- Prior low back Fusion: having a lower lumbar fusion causes increased stresses onto the SI joint. For example, a fusion at L5-S1 may cause more pressure to be applied to the SI joint because the fused levels are now immobile and act as a unit.
- Contact sports or stressful jobs: Jobs that overload the SI joint, such as football (squatting) or construction may cause the SI joint to wear out quicker than normal.
- Trauma: injuries such as falls or vigorous exercise can lead to SI joint pain
- Autoimmune disorders: certain autoimmune disorders can lead to SI joint dysfunction and pain. These include ankylosing spondylitis, juvenile rheumatoid arthritis, reuters syndrome, and psoriatic arthritis.
What are symptoms of SI joint pain?
Common symptoms of SI joint pain include:
- Constant low back pain
- Pain which radiates to the bottom of the leg, such as sciatica
- Pain localized to the low back, pelvis, buttocks, groin
- Pain when sitting or moving your legs, such as when walking
- Instability, such as a feeling your legs will give out or buckle
- Increased pain when standing up from a sitting position
- Pain and inability to sit for long periods or sitting on one side.
How is SI joint pain diagnosed?
SI joint pain may be difficult to diagnose, because the symptoms may mimic other conditions, such as facet joint arthritis, hip arthritis, or lumbar disc herniation–all which can cause low back pain. In addition, damage to the joints doesn’t show up on imaging tests such as a X-ray, MRI, or CT scan. The diagnosis typically involves a thorough physical exam plus a diagnostic injection to the SI joint. This is the most widely used method to accurately diagnose SI joint syndrome. If the SI joint pain is relieved with a steroid injection, this confirms SI joint pain as the cause.
In addition to collecting a detailed medical history, there are some physical exam maneuvers that may help diagnose the SI joint as the cause of pain. These include palpating the SI joint, and certain lower leg maneuvers to attempt to reproduce the pain.
Imaging may be used to rule out other causes of low back pain, such as x-rays to identify occult fractures and MRIs to identify herniated discs and facet joint pathology.
The best test to isolate SI joint pain is to do an SI joint injection, which can not only be diagnostic but therapeutic.
How is SI joint pain treated?
Most patients with SI joint pathology can be treated successfully with conservative treatments. Physical therapy, low impact exercises like yoga or pilates, and massage can help stabilize and strengthen the SI joints and ease pain.
Level 1 Conservative Treatments:
- Physical therapy
- Home exercises
- Chiropractic therapy
- Oral medications to relieve the pain
- Ibuprofen
- Naproxen
- Steroids
- Muscle relaxants
- Pain patches
- Ice and heat.
Level II – SI Joint Injections
- Steroid injections
- Outpatient procedure
- Done with x-ray guidance
- 1-3 injections may be needed
This involves injecting a small amount of numbing medication into the SI joint using fluoroscopic guidance.
If your pain reduces by >50% after the injection, then this is considered a positive or confirmatory diagnostic injection. This means your SI joint is most likely the cause of your pain.
If the level of pain does not change after injection, then the SI joint is less likely to be the primary cause.
Level III – Surgery
Surgery is always used as a last resort. If conservative treatments fail, then a minimally invasive SI fusion may be an option.
- Sacroiliac joint fusion: This is a minimally invasive, outpatient procedure that involves carefully placing metal screws across the SI joint, so the bones fuse and grow together. Fusing the joint helps to alleviate the pain associated with excess movement. Learn more about SI joint Fusion
Frequently asked questions
How can I prevent SI joint pain?
Some causes of SI joint pain are not preventable. Exercising regularly, maintaining a healthy body weight and lifestyle can help slow the progression of SI joint degeneration.
Why is SI joint dysfunction so hard to diagnose?
There are many different causes of back pain and there can be lots of overlap between the hip and spine. In addition, there are several physical exam findings in patients with SI joint pain but none are very sensitive or specific. A combination of history, physical exam and imaging findings, along with diagnostic injections help make the diagnosis.
Can pain from the SI joint cause leg pain?
Yes, pain from the SI joint can cause pain, numbness or weakness which can radiate down into the thighs and upper legs.