Sacroiliac Joint Pain: Causes, Diagnosis and Treatment

Sacroiliac Joint Pain: Causes, Diagnosis and Treatment

Sacroiliac (SI) joint pain is a frequently overlooked cause of low back pain, responsible for an estimated 15–30% of all chronic low back pain. Many patients spend years being treated for lumbar disc disease or sciatica without realising their pain originates from the SI joint. Understanding this condition can lead to faster diagnosis and more effective treatment.

What Is the Sacroiliac Joint?

The sacroiliac joint connects the sacrum (the triangular bone at the base of the spine) to the iliac bones (the large bones of the pelvis) on each side. There are two SI joints — one on each side of the lower spine, just above the tailbone.

The SI joints are strong, load-bearing joints with limited movement. They transmit forces between the spine and legs and absorb shock during walking, running, and lifting. They are reinforced by powerful ligaments and are stabilised by surrounding muscles.

Causes of SI Joint Pain

SI joint dysfunction can result from:

Inflammation (sacroiliitis): Autoimmune conditions such as ankylosing spondylitis, psoriatic arthritis, inflammatory bowel disease-related arthritis, and reactive arthritis commonly cause SI joint inflammation. This is important to identify as it requires specific treatment.

Osteoarthritis: Age-related degenerative changes in the SI joint cartilage.

Pregnancy and postpartum: Hormonal changes (relaxin) loosen pelvic ligaments, increasing SI joint mobility and causing pain. Postpartum SI joint pain is very common.

Trauma: Falls landing on the buttocks, road traffic accidents.

Leg length discrepancy: Unequal leg lengths alter gait and stress the SI joints asymmetrically.

Previous lumbar fusion surgery: After spinal fusion surgery, the SI joint often takes on increased mechanical load — called adjacent segment disease.

Symptoms

SI joint pain typically presents as:

- Deep, aching pain in the lower back or buttock, usually on one side

- Pain that may radiate into the groin, hip, or thigh (rarely below the knee — unlike typical sciatica)

- Stiffness and reduced mobility in the lower back

- Pain worsened by prolonged standing, walking, climbing stairs, or rolling over in bed

- Relief with lying down

SI joint pain is often confused with hip joint pain, lumbar disc pain, or piriformis syndrome. Careful clinical examination is essential.

Diagnosis

Diagnosis is clinical (based on history and physical examination) combined with imaging and, most importantly, a diagnostic injection.

Physical examination: Several provocative tests stress the SI joint:

- FABER test (Patrick's test): Flexion, Abduction, External Rotation of the hip

- FADIR test

- Posterior pelvic pain provocation test

- Gaenslen's test

- Distraction and compression tests

No single test is definitive, but a positive cluster of multiple tests increases diagnostic accuracy.

Imaging: X-rays may show sacroiliitis (joint space narrowing, sclerosis). MRI is essential for detecting active inflammation (bone marrow oedema on STIR sequences) in inflammatory arthritis. CT shows bony detail.

Diagnostic SI joint injection: The gold standard for confirming SI joint as the pain source is an image-guided injection of local anaesthetic into the joint. Relief of 50–75% or more confirms the diagnosis.

Blood tests: If inflammatory sacroiliitis is suspected, tests including HLA-B27, ESR, CRP, and rheumatology referral are essential.

Treatment

Conservative Treatment

Physiotherapy: SI joint stabilisation exercises targeting the gluteal, core, and hip muscles. A physiotherapist with pelvic pain experience is ideal.

SI joint belt: A compressive belt worn around the pelvis improves joint stability and can significantly reduce pain, particularly in pregnancy-related dysfunction.

Medications: NSAIDs for pain and inflammation. Disease-modifying drugs (DMARDs, biologics) for inflammatory sacroiliitis under rheumatology guidance.

Heat and manual therapy: Can provide symptomatic relief.

Interventional Treatment

Image-guided SI joint injection: Injecting corticosteroid into the SI joint under fluoroscopy or CT guidance provides significant relief for weeks to months in inflammatory and degenerative SI joint pain.

Periarticular injection: Injections around rather than into the joint target the posterior SI ligaments, which are richly innervated and often the source of pain.

Radiofrequency ablation (RFA): For longer-lasting relief, RFA of the lateral branches of the dorsal rami (nerves supplying the SI joint) can provide 6–18 months of relief. This is an excellent option for patients who respond well to injections but need more durable results.

Surgical Treatment

SI joint fusion surgery is reserved for severe, refractory cases where extensive conservative and interventional treatment has failed. Minimally invasive SI joint fusion devices have improved outcomes significantly.

Conclusion

SI joint pain is a real, diagnosable, and treatable condition. If you have low back or buttock pain that has not responded to lumbar disc treatments, ask your doctor to evaluate your sacroiliac joints. With accurate diagnosis and a tailored treatment plan, most patients achieve excellent relief.s