The sacroiliac (SI) joint

The less known pain generator of the lumbar spine


The SI joint is located between the ilium (pelvis) and the sacrum (spine). It is the link between the spine and the hip.

Anatomy of the lumbosacral spine, pelvis, and joints

SI joint pain (sacroileitis) is usually caused by an inflammatory response of the SI joint and can have many causes. Most sacroileitis are caused by an overload of the joint, either by excessive stiffness of the lumbar spine (e.g. after spine fusion with instrumented stabilization of the lumbar discs, etc.), by a difference in length of the legs (leading to a pelvic tilt and its overload), etc. The typical pain pattern of SI joint pain is of a pain usually located in the buttock of the affected side that may radiate from the back and/or front all the way from the thigh to the knee. Many patients describe it as a continuous pain that is exacerbated especially in postural changes, walking and in some cases even when the patient is seated.

Right sacroileitis (inflammation of the sacroiliac joint) due to leg length difference with a pelvic tilt to the left

It is therefore common that the pain caused by a SI joint is mistaken with pain caused by the lumbar spine.

In most cases, radiological tests (conventional X-rays, MRIs, CT scans of the lumosacral spine) do not allow a reliable diagnosis of SI joint pain.

The diagnosis of SI joint pain is a clinical diagnosis and requires a thorough physical examination of the SI joint by a physician with several provocative tests. In order to avoid unnecessary surgery of the lumbar spine, disorders of the sacroiliac joint must be taken very seriously in the diagnosis of low back pain and radicular pain (i.e. caused by a disk herniation).


International accreditation (USA) of Dr. Morgenstern as a surgeon trained in spinal interventions and infiltrations.

International accreditation (USA) of Dr. Morgenstern as a surgeon trained in spinal interventions and infiltrations.
International accreditation (Germany) of Dr. Morgenstern as a surgeon trained in percutaneous fusion of the SI joint.

Conservative treatment

Intra-articular infiltration of the SI joint

Conservative treatment of SI joint pain includes rest, physiotherapy and pain medication. However, the most effective treatment for SI joint pain usually is an intra-articular infiltration of the SI-joint with a combination of corticosteroids and local analgesics, which immediately relieves the pain and decreases the inflammation.

Example of an intra-articular infiltration of the right sacroiliac joint

Dr. Morgenstern performs intra-articular infiltrations of the sacroiliac joint using a new intra-articular infiltration technique developed in German that allows the joint to be infiltrated on an outpatient basis, without the need of contrast medium and operating room (which are usually necessary for other, popular infiltration techniques).

The analgesic effects of the SI joint infiltration are usually immediate. Still, two infiltrations are usually recommended with a time interval of 2 to 3 weeks in order to significantly reduce inflammation of the affected sacroiliac joint and decrease the pain for a long period of time.

Surgical treatment

Percutaneous fusion of the SI joint

Surgical treatment of the painful SI joint is indicated only in cases where conservative therapy has failed for longer than 6 months. If the chronic SI joint pain persists, minimally invasive surgery can be performed: it consists of the percutaneous placement of three triangular titanium implants that block the ilium and sacrum bones, blocking the SI joint in all its degrees of freedom.

In recent years, more than 30,000 procedures have been performed worldwide. Clinical studies show a significant improvement in a patient’s quality of life after surgery compared to patients treated without surgery.

Characterization of percutaneous surgical fusion of the left sacro-iliac joint by means of 3 titanium implants with triangular profile.

Dr. Morgenstern is an accredited surgeon for the percutaneous fusion of the sacroiliac joints.

© Copyright – Morgenstern Institute of Spine, 2019.