The prevalence of sacroiliac (SI) joint dysfunction is approximately 25% in adult patients with chronic low back pain.¹ Pain can be unilateral or bilateral but usually not midline.² Women are more likely to present with SI joint dysfunction than men.³ The SI joint in women is more mobile compared with the SI joint in men, resulting in larger stress, load, and pelvic ligament strain.⁴ SI joint dysfunction is common in pregnant and postpartum patients.⁵

Etiology and Differential Diagnosis

The SI joint serves as a shock absorber and transfers vertical loads from the lumbar spine to the lower extremities during bending movements. The etiology of SI joint dysfunction is not well understood. The SI joint may be the primary source of pain, or dysfunction at the joint or surrounding structures may affect the joint’s load transfer function and produce a painful stimulus.⁶

SI joint dysfunction can be associated with osteoarthritis or inflammatory conditions such as ankylosing spondylitis, posttraumatic arthritis, and other spondyloarthropathies.⁷ Similarly, mechanical faults at the pubic symphysis or SI joint can result in pelvic asymmetry or joint instability. Nonoptimal load transfer is seen in patients with SI joint stiffness (hypomobility) and patients with insufficient pelvic girdle stability (hypermobility).⁸ Table 1 presents the differential diagnoses of conditions with similar or overlapping signs and symptoms of SI joint dysfunction.^9–11

History and Physical Examination

Differentiating SI joint dysfunction from other diagnoses presenting with low back pain requires a complete history and physical examination of the spine, pelvic girdle, and hips as well as a review of other systems to rule out red flags such as history of trauma, unexplained weight loss, fever, bowel and bladder changes, cancer, and night pain.^6,12,13

Patients with SI joint dysfunction may present with pain that is localized to the area at or just inferomedial to the posterior superior iliac spine as demonstrated in a Fortin finger test (Figure 1) or along the gluteal area, lateral hip, lower extremities, and groin.^2,12 Potential aggravating factors and activities that may exacerbate pain from SI joint dysfunction are described in Table 2.^3,12

SI joint dysfunction may be attributed to a variety of causes.¹² Traumatic onset commonly occurs with heavy lifting, a fall onto the buttocks, and motor vehicle collisions. A more insidious onset can be caused by recreational activities with repeated weight bearing and shear or torsional forces experienced during sports such as football, gymnastics, and golfing.

A physical examination should include gait analysis (i.e., reporting of pain with walking, shortened stride length, antalgic gait), range of motion, provocation testing, strength, flexibility, and palpation assessments (Table 3).^{2,3,12,14–16} Lower extremity neurologic screening (i.e., reflexes, sensation, strength, straight leg raise) is helpful when considering differential diagnoses.

Motion and provocation tests can assess the SI joint for dysfunction and pain reproduction^6,17 (Figure 2, Figure 3, Figure 4, Figure 5, and Figure 6). A video demonstration is available at https://www.youtube.com/watch?v=8biQsdgdyzA.