The sacroiliac joint (SI joint) is another potential cause of low back and leg pain. The spine physician uses specific manual maneuvers to test the SI joints. Depending on the patient’s response to the physician’s movements of the back and legs, one or both SI joints may be suspected or confirmed as the pain source.
What are the sacroiliac joints?
The SI joint is a semi-mobile joint formed by the attachment of the sacrum (ie, tail bone) and the iliac crest (ie, hip bones). See illustration below.
During pregnancy, female hormones are released to enable the SI joint ligaments to become mobile, allowing the pelvis to expand and accommodate the baby’s head during delivery. This may be why sacroiliac joint arthritis and associated pain is more common in middle-aged women. However, SI joint pain does affect men too.
Characteristics of Sacroiliac Joint Pain
SI joint pain typically causes pain over the lower, lateral (ie, side) aspect of the lower back. Pain may radiate into the buttock and upper posterior thigh (ie, back of the affected thigh). An examination of the SI joints typically involves the physician palpating (eg, pressing on, touching) one or both sacroiliac joints, which may reliably reproduce the patient’s pain and symptoms (eg, radicular pain).
SI Joint Injection
Figure 1 (below), depicts a SI joint injection or sacroiliac nerve block. Through the spinal needle, a local anesthetic and corticosteroid medication are injected. Similar to the facet joint injection, the SI joint injection provides diagnostic information—confirming or denying the SI joint as the pain generator. If the injection relieves the patient’s pain, the pain generator or cause is confirmed.
Epidural injections, facet joint and sacroiliac joint injections or nerve blocks are representative of a few of the different back pain-relieving procedures a pain management physician offers. An experienced physician relies on a thorough history to understand a patient’s pain pattern and its likely cause or source. X-rays and MRI or CT scan studies are performed to confirm the diagnosis.
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