What Are SI Joint Injections?
The sacroiliac joint connects the sacrum, the triangular bone at the base of the spine, to the iliac bone of the pelvis on each side of the body. Like any synovial joint, it is susceptible to inflammation, degeneration, and destabilization, producing pain that is regularly misattributed to lumbar spine pathology because the two conditions can look nearly identical on clinical presentation.
An SI joint injection delivers a combination of local anesthetic and corticosteroid directly into the joint space. The anesthetic produces rapid short-term relief that gives the clinical team information imaging cannot provide: whether this specific joint is genuinely responsible for the patient's symptoms. The corticosteroid follows with a slower, more sustained anti-inflammatory effect that can last from several weeks to several months.
Diagnostic Versus Therapeutic Purpose
SI joint injections serve two complementary functions that are both clinically valuable.
As a diagnostic tool, the anesthetic component tests directly whether the SI joint is the primary pain source. A meaningful reduction in symptoms following the injection points clearly to the joint as the driver and gives the care team the diagnostic clarity needed to direct further treatment with confidence.
As a therapeutic intervention, the corticosteroid targets the joint inflammation producing the pain, providing relief that supports physical therapy participation and functional recovery. The patient's response to both components informs the broader management plan going forward.
How SI Joint Injections Fit Into a Broader Treatment Plan
For patients with confirmed SI joint pain, injections are typically one component of a broader strategy that also includes physical therapy addressing the muscular imbalance and pelvic instability that commonly accompany SI joint dysfunction. When injections confirm the SI joint as the source but relief proves temporary, surgical stabilization through SI joint fusion may be discussed as a more definitive, longer-term solution.