Image-Guided Intra-Articular Versus Periarticular Injection in Sacroiliac Joint Pain

Sacroiliac joint (SIJ) pain is a common cause of chronic low back pain that can arise from within the joint itself or from the surrounding ligaments and supporting soft tissues. Image-guided injections using corticosteroids and local anesthetics are widely used to treat SIJ pain when physical therapy or medications fail. However, it remains uncertain whether administering the injection directly inside the joint space (intra-articular) or into the surrounding posterior ligaments (periarticular) provides greater early pain relief and functional recovery. The primary purpose of this clinical trial is to compare the efficacy, safety, and functional outcomes of fluoroscopy-guided intra-articular versus periarticular injections in adult patients with chronic sacroiliac joint pain. Participants are randomly assigned in a 1:1 ratio to receive one of two fluoroscopy-guided procedures: * Intra-Articular Injection Group: Participants receive an injection of methylprednisolone acetate and bupivacaine delivered directly into the synovial space of the sacroiliac joint under fluoroscopic guidance, confirmed with radiographic contrast. * Periarticular Injection Group: Participants receive an injection of methylprednisolone acetate and bupivacaine deposited along the posterior sacroiliac ligament complex and outer capsule under fluoroscopic guidance. All participants are followed for 8 weeks after the procedure. Changes in pain intensity are tracked using the Numeric Rating Scale (NRS) at baseline, 2 weeks, 4 weeks, and 8 weeks. Physical function and daily activity impairment are measured using the Oswestry Disability Index (ODI) at baseline, 4 weeks, and 8 weeks. Patient global improvement, side effects, and rescue pain medication consumption will also be monitored throughout the study period.

Inclusion Criteria: * Adult patients aged 18 to 70 years * Clinical diagnosis of sacroiliac joint (SIJ) pain confirmed by at least 3 positive provocation tests out of 5 (FABER, Gaenslen's, thigh thrust, compression, or distraction tests) * Chronic SIJ pain with a symptom duration of at least 3 months * Pain intensity score of at least 4 out of 10 on the Numeric Rating Scale (NRS ≥ 4/10) at enrollment * Failure of conservative management (physiotherapy and/or NSAIDs for at least 6 weeks) * Willingness and ability to provide written informed consent Exclusion Criteria: * Known coagulopathy or current anticoagulant therapy that cannot be safely bridged * Active local infection at the injection site or systemic infection * Known hypersensitivity or allergy to corticosteroids, local anesthetics, or contrast media * History of prior SIJ surgery or joint fusion * Previous sacroiliac joint injection within the last 3 months * Pregnancy or breastfeeding * Severe spinal or pelvic deformity preventing safe and accurate needle placement * Significant cognitive impairment precluding informed consent or reliable outcome reporting * Active malignancy involving the pelvis or sacrum