The sacroiliac (SI) joint connects the spine to the pelvis, acting as a shock absorber and weight-bearing structure that transfers forces between the upper body and the legs. Sacroiliac joint pain arises from inflammation or dysfunction within this joint and can account for up to 25% of chronic lower back pain cases. When conservative treatments like physical therapy and oral medications fail, a sacroiliac joint injection is a common, minimally invasive procedure. This injection serves both a diagnostic role to confirm the pain source and a therapeutic role to reduce localized inflammation.
Purpose and Components of the Injection
A sacroiliac joint injection is designed to serve a dual function in patient care: diagnosis and treatment. The diagnostic purpose is fulfilled by injecting a local anesthetic, such as lidocaine or bupivacaine, directly into the SI joint space. If the patient experiences significant, immediate relief after the anesthetic takes effect, it confirms the SI joint is the true source of the pain.
For therapeutic benefit, the injection mixture typically includes a corticosteroid medication, such as triamcinolone or dexamethasone, combined with the anesthetic. The anesthetic provides rapid, temporary numbing of the joint, while the corticosteroid is a powerful anti-inflammatory agent. The steroid decreases inflammation within the joint capsule, which is responsible for the longer-term pain relief.
Typical Duration of Pain Relief
The duration of pain relief following a sacroiliac joint injection is highly variable among individuals. The initial, immediate relief felt within hours is due to the local anesthetic, which wears off quickly, often within a day. The original pain commonly returns temporarily after the anesthetic fades, before the steroid component begins its work.
The corticosteroid typically begins to take effect within a few days to a week after the injection. Once active, the pain relief provided by the anti-inflammatory action can last from a few weeks to several months. Many patients report a reduced level of pain for an average of two to four months, though relief can extend up to six months or longer in some responders.
Factors Influencing Efficacy
The wide range of pain relief duration is influenced by a combination of patient-specific and procedural factors. The underlying cause of the pain plays a significant part; relief may be shorter if the dysfunction is due to severe joint degeneration or structural instability rather than acute inflammation. The precision of the injection technique is also highly relevant, requiring image guidance like fluoroscopy or CT scans to ensure accurate medication delivery.
The individual’s biological response to the corticosteroid is another variable that cannot be predicted, as some bodies process the medication more quickly or respond less robustly. Adherence to a follow-up treatment plan, particularly physical therapy and activity modification, significantly impacts the longevity of the relief. Using the pain-free window to strengthen stabilizing muscles is necessary to prevent symptom recurrence.
Post-Injection Treatment Strategy
A sacroiliac joint injection is rarely a standalone treatment and is integrated into a comprehensive management strategy. Due to the potential risks associated with repeated steroid exposure, doctors typically limit the number of therapeutic injections. Patients are generally advised to receive no more than two to three SI joint injections within a 12-month period.
The most important step after a successful injection is engaging in a physical therapy program. The temporary relief provides an opportunity to strengthen the muscles that support the pelvis and spine, addressing the mechanical issues that contributed to the pain. If injections provide insufficient or short-lived relief, other options may be considered, such as radiofrequency ablation, or, in persistent cases, minimally invasive SI joint fusion surgery.