Sacroiliac Joint Fusion: How It Works & Recovery

Sacroiliac joint fusion is a procedure that stabilises a painful sacroiliac (SI) joint — the joint between the base of the spine and the pelvis — by placing small implants across it to reduce abnormal movement. It is generally reserved for carefully selected patients in whom the SI joint has been confirmed as the source of pain and non-surgical treatment has not provided lasting relief. This page explains how the procedure works, who it may suit, and what recovery involves, as general education rather than personal medical advice. It describes the operation itself, distinct from the broader topic of sacroiliac joint pain.

What is sacroiliac joint fusion?

The sacroiliac joints sit on either side of the lower spine, connecting the sacrum to the pelvis. They normally move only a small amount and transfer load between the spine and the legs. When a joint becomes a persistent source of pain, fusion aims to stabilise it.

In a fusion, small implants are placed across the joint to limit movement, and bone is encouraged to grow across the joint so that it gradually stiffens into a stable unit. Most modern procedures use a minimally invasive approach through a small incision, guided by X-ray imaging.

Who is a candidate? (Indications)

This procedure is considered only after the SI joint has been carefully confirmed as the source of pain. Typical features include:

• Pain localised to the region of the SI joint, often in the buttock, that can radiate into the back of the thigh.
• Reproduction of the pain on specific examination tests.
• Meaningful, if temporary, relief from a guided diagnostic injection into the joint.
• Persistent symptoms despite an adequate trial of non-surgical care, such as physiotherapy, activity modification, medication and spinal injections.

Because pain in this region can have several causes, thorough diagnosis is essential before surgery is considered. Suitability is decided individually.

How the procedure is performed

1. Anaesthesia and positioning. The procedure is usually performed under general anaesthesia with the patient lying face-down.
2. Imaging guidance. X-ray imaging is used throughout to plan and confirm implant positions.
3. Small incision. A short incision is made over the side of the pelvis to reach the joint.
4. Joint preparation. The path across the joint is prepared for the implants.
5. Implant placement. One or more implants are placed across the SI joint to reduce movement and provide stability.
6. Encouraging fusion. The implants and, where used, bone graft help bone to grow across the joint over time.
7. Closure. The small incision is closed, typically with minimal stitching.

Benefits and risks

Possible benefits. The aim is to reduce the abnormal movement thought to drive the pain, providing stability and, in suitable patients, relief of long-standing SI joint pain. The minimally invasive approach aims to limit tissue disruption and support earlier recovery.

Risks and limitations. As with any surgery, there are real risks, including:

• Infection or wound problems.
• Bleeding.
• Nerve irritation or injury, with possible numbness, tingling or weakness.
• Implant malposition or loosening.
• Continued pain, especially if another structure also contributes to symptoms.
• Failure of the joint to fully fuse.

Because pain in this area can be multifactorial, careful patient selection is critical, and complete relief cannot be guaranteed.

Alternatives

Non-surgical care is the usual first approach and may include physiotherapy focused on the pelvis and core, activity modification, medication, and spinal injections into or around the joint. Some patients gain useful relief from these measures alone. Where pain persists and the joint is confirmed as the source, fusion may be discussed. The right path depends on the certainty of diagnosis and the response to earlier treatment.

Recovery and outlook

Recovery is gradual and individual.

• Early days: Many patients walk soon after surgery, often with limited weight-bearing on the treated side and the use of crutches for a period.
• First weeks: Protected activity, wound care and avoidance of high-impact movements.
• Following months: Activity is progressively increased, often with physiotherapy, as bone fusion across the joint develops over several months.

Some patients experience meaningful, lasting relief, while others improve only partly. Outcomes are individual and depend strongly on accurate diagnosis.

When to seek a specialist opinion

Consider a specialist assessment if you have persistent buttock or lower-back pain localised to the SI joint that limits daily life and has not responded to appropriate non-surgical treatment. Seek urgent medical attention for new leg weakness, numbness around the groin or buttocks, or loss of bladder or bowel control, as these suggest a different and potentially serious problem. A specialist can confirm whether the SI joint is the source of pain and whether fusion is appropriate.