Sakroiliitis

Sakroiliitis refers to inflammation of one or both sacroiliac joints, which connect the sacrum at the base of the spine to the ilium of the pelvis. The condition can be inflammatory, often associated with spondyloarthropathies such as axial spondyloarthritis or psoriatic arthritis, or noninflammatory, arising from mechanical overuse, degenerative changes, pregnancy, or infection.

Causes and subtypes include inflammatory sacroiliitis, typically presenting with inflammatory back pain and swelling, and infectious sacroiliitis, which requires urgent treatment. Mechanical sacroiliitis results from stress or trauma to the joint, overloading during exercise, pregnancy-related joint laxity, or osteoarthritis. Less commonly, it may accompany conditions such as gout or Reiter’s syndrome. Risk factors for inflammatory sacroiliitis include HLA-B27 positivity and a family history of spondyloarthropathies.

Symptoms commonly involve lower back and buttock pain that may radiate to the thigh, worsens with standing or walking, improves with rest, and is often associated with morning stiffness. Tenderness over the sacroiliac joints can be elicited on examination, and pain may be triggered by certain movements or positions.

Diagnosis relies on clinical assessment, imaging, and laboratory tests. MRI is sensitive for detecting active inflammation, while X-ray and CT can reveal structural changes such as sclerosis or erosions. Laboratory studies may show elevated inflammatory markers (ESR, CRP) and, in inflammatory cases, HLA-B27 positivity. Exclusion of infection and other spinal disorders is important.

Treatment depends on cause. Inflammatory sacroiliitis is typically treated with NSAIDs, physical therapy, and, in refractory cases, biologic agents such as TNF or IL-17 inhibitors. Infectious sacroiliitis requires antibiotics, and mechanical forms are managed with activity modification, targeted therapy, injections, or physical therapy. Prognosis varies with underlying disease and response to therapy.