Sacroiliitis is inflammation of the sacroiliac (SI) joint in the pelvic region of your body. This can lead to symptoms of pain in the lower back and buttocks. Sacroiliitis can be caused by several ...

Psoriatic arthritis is an autoimmune condition. It happens when your body’s immune system attacks healthy tissue by mistake.

Ankylosing spondylitis is a type of arthritis that primarily affects the spine. Symptoms of this lifelong condition usually begin in early adulthood and include pain and stiffness in the lower back.