Sacroiliac Joint Pain: Causes, Diagnosis and Treatment

Pain in the lower back that seems to sit just to one side of the spine, near the dimple above the buttock, is often blamed on the lumbar spine. In a meaningful number of people, however, the source is the sacroiliac (SI) joint, where the base of the spine meets the pelvis. SI joint pain can be stubborn, but it is also very treatable with conservative care. This article explains what the SI joint does, why it becomes painful, how clinicians identify it and which treatments help.

What Is the Sacroiliac Joint?

You have two sacroiliac joints, one on each side of the pelvis. Each joins the sacrum, the triangular bone at the base of the spine, to the ilium, the large wing-shaped bone of the pelvis. The SI joints are strong, stable joints held together by some of the toughest ligaments in the body. They move only a few millimeters, but that small amount of motion is important for absorbing shock and transferring forces between the upper body and the legs during walking, running and lifting.

How Common Is SI Joint Pain?

Research estimates vary, but the sacroiliac joint is thought to be the main source of pain in roughly 15 to 30 percent of people with persistent low back pain. It is more common during and after pregnancy, after a fall onto the buttocks, and in people who have had a lumbar fusion, which can increase the load on the SI joints.

Common Causes

• Trauma: a fall onto the buttocks, a misstep off a curb, or a motor vehicle accident, especially when the foot is braced on the brake pedal
• Repetitive strain: running, jumping and sports that load one leg more than the other
• Pregnancy: hormonal changes relax the pelvic ligaments, and weight and posture change as pregnancy progresses
• Leg length differences or altered walking patterns, for example after an injury
• Arthritis: degenerative changes with age, and inflammatory conditions such as axial spondyloarthritis, which can cause sacroiliitis
• Previous spinal fusion that shifts load to the pelvis

Tailbone pain is a related but different problem; Dr. Lehman's case report on coccygodynia describes post-traumatic pain at the base of the spine.

Typical Symptoms

• Pain on one side of the lower back or buttock, near the bony bump at the back of the pelvis
• Pain that may spread into the groin, hip or back of the thigh, usually stopping above the knee
• Pain when rising from sitting, climbing stairs, getting in and out of a car, or rolling over in bed
• Pain when standing on one leg or putting more weight on the affected side
• Stiffness, particularly in the morning or after sitting

SI joint pain does not usually cause true numbness or muscle weakness. Leg pain that travels below the knee with numbness or tingling is more suggestive of a nerve root problem such as sciatica.

How SI Joint Pain Is Diagnosed

There is no single perfect test for SI joint pain, so clinicians piece together several findings:

• History: the location of pain (often the patient points to the area just below the belt line to one side, sometimes called the "Fortin finger sign"), the mechanism of injury and aggravating activities.
• Pain provocation tests: a set of examination maneuvers, such as the distraction, thigh thrust, compression, sacral thrust and Gaenslen's tests, gently stress the joint. When several tests reproduce the familiar pain, SI joint involvement becomes more likely, although no test cluster is definitive.
• Ruling out other causes: the lumbar spine, hip joint and nerve roots are examined, including reflexes, strength and sensation.
• Imaging: X-rays or MRI are not needed for most people but may be ordered if an inflammatory condition, fracture or other problem is suspected. Inflammatory back pain, which often starts before age 45, involves morning stiffness and improves with exercise, should be evaluated by a medical doctor.
• Diagnostic injection: in persistent cases, a specialist may inject numbing medication into the joint under image guidance to see whether it relieves the pain.

Conservative Treatment Options

Manual therapy

Chiropractic physicians commonly treat SI joint pain with manipulation or mobilization of the joint and lower back, along with soft-tissue therapy for surrounding muscles such as the gluteals, piriformis and hip flexors. Many patients find this helps reduce pain and improve movement, particularly when combined with exercise. To learn what a visit involves, read your first chiropractic visit: what to expect.

Stabilizing and strengthening exercise

Because the SI joint relies on muscles and ligaments for stability, strengthening is a key part of recovery. Programs often include:

• Gluteal strengthening, such as bridges and side-lying leg raises
• Deep abdominal and pelvic floor activation
• Hip mobility and gentle stretching of tight muscles
• Gradual return to walking, running or sport with attention to symmetry

Pelvic support belts

An SI belt worn around the pelvis, just below the waist, can provide compression and short-term relief for some people, especially during pregnancy or during flare-ups. Belts are typically used as a temporary aid alongside exercise rather than as a long-term solution.

Activity modification and self-care

• Avoid prolonged standing on one leg or crossing your legs while sitting
• Take shorter steps and use a handrail on stairs during flare-ups
• Get in and out of the car by sitting first, then swinging both legs together
• Sleep on your side with a pillow between your knees; see our guide to sleeping positions for back pain
• Use heat or ice for comfort

Medical treatments for persistent pain

When pain persists despite a good trial of conservative care, a medical doctor may discuss anti-inflammatory medication, an image-guided corticosteroid injection or radiofrequency treatment. SI joint fusion surgery is reserved for a small number of carefully selected patients with severe, long-lasting pain confirmed as coming from the joint. Inflammatory sacroiliitis is managed by a rheumatologist, often with specific medications.

Preventing Flare-Ups

• Keep the hip and core muscles strong with regular exercise
• Warm up before sports and increase training loads gradually
• Lift with good technique, keeping the load close and avoiding twisting
• Break up long periods of sitting; an ergonomic workstation helps
• During pregnancy, ask your prenatal care provider about safe exercises and support

When to Seek Care

Book an evaluation if pain on one side of the lower back or buttock lasts more than a couple of weeks, keeps coming back, or limits walking, sitting or sleep. Seek prompt medical care if pain comes with fever, unexplained weight loss, a history of cancer, bladder or bowel changes, or numbness around the groin, as explained in our guide to back pain red flags.

Conclusion

The sacroiliac joint is a common but often overlooked source of lower back and buttock pain. A careful history and a cluster of examination tests help identify it, and most people improve with conservative care: manual therapy, targeted strengthening, sensible activity changes and, in some cases, a pelvic belt. If your pain is persistent or unclear, a licensed chiropractic physician or medical doctor can help pinpoint the source and guide your recovery.

Medical disclaimer: This article is for general education and is not a substitute for personalized advice from a licensed health care provider. If you have severe, worsening or unusual symptoms, seek medical care promptly.