The pain on both sides of the lower back and upper buttocks can be caused by the following reasons: first, rheumatoid, when rheumatoid involves the sacroiliac joints, there can be pain at the sacroiliac joints on both sides of the upper buttocks and lower back, often as soreness, when the sacroiliac joints and lumbar spine X-rays should be examined, early blood tests to diagnose and treat. Secondly, ankylosing spondylitis, ankylosing spondylitis can also have bilateral pain in the sacroiliac joints above the buttocks and below the waist, which can involve the entire spine, and can have morning stiffness, which should be diagnosed and treated early with blood tests and X-rays of the sacroiliac joints and spine, and MRI. Thirdly, fasciitis of the gluteal muscle, when there is fasciitis of the gluteal muscle, there can also be symptoms of soreness of the fascia on both sides of the buttocks, and the soreness is more obvious when you are cold and tired, so it is necessary to conduct early physical examination to diagnose and early oral medication and physical therapy.