The sacroiliac joint is a joint that connects the spinal column with the pelvis. The V-shaped sacrum near the base of the spine fits like a wedge between the wide wings of the ilium (hipbone). Ligaments and cartilaginous plates connect the bones.
Little movement occurs about the sacroilliac joint but it may be affected by certain types of arthritis, such as ankylosing spondylitis. Inflammation or strain on the sacroiliac joint often causes lower back pain.
Inflammation of the sacroiliac joint is called sacroilitis. It can be due to various disorders, such as anklyosing spondylitis, Reiter's syndrome, rheumatoid arthritis, or arthritis associated with psoriasis. The main symptom is lower back pain, and pain in the buttocks, groin, and back of the thigh. Treatment is with non-steroidal anti-inflammatory drugs.