What is sacroiliitis?

Sacroiliitis is an inflammation or poor mechanical function of the sacroiliac joint, that causes low back pain. It is estimated that between 15-20% of diagnosed cases of low back pain have their source in this joint rather than the lumbar spine. For this reason it is crucial to determine if the sacroiliac joint is the source of the problem, but this cannot be done by a radiological test.

The sacroiliac joint is the largest joint in the human body. It is the one that joins the sacrum with the iliac bone of the pelvis. We have two sacroiliac joints, one on each side. Although we call it a joint, its function is not to articulate movement, but to support or bear the mechanical load of the upper body on the pelvis.

There is only one physiological situation in a human life in which this joint moves, and that is in women, as during the final stages of pregnancy and when giving birth, the sacroiliac joints stretch, widening the pelvis to make giving birth possible.

Causes of sacroiliitis

There are several causes of sacroiliac joint pain. Since the pain is very similar to low back pain originating from the spine, it is very important to ask the patient how the pain started, because this information will help us determine possible the origin of the pain.

Injury (the most frequent cause)

  • A fall landing on the buttocks
  • Motorcycle accident with a lateral blow to the hip
  • Car accident with a blow to the side or back
  • Carrying excessive weight or carrying weight too often
  • Childbirth

Causes other than injury

  • Previous lumbar fusion surgery (the most frequent cause other than injury)
  • Changes to the body’s equilibrium 
  • Multiple pregnancies

Symptoms of sacroiliitis

The symptoms of sacroiliitis are very similar to the symptoms of low back pain coming from the spine, which is why it is often hard to diagnose it correctly. It can also be accompanied by a pseudo-sciatica, since the sciatic nerve starts in the lower spine and then runs just underneath the sacroiliac joint, making the diagnosis even more complicated.

As we have mentioned, the sacroiliac is the largest joint in the body, so when it is injured, it will cause very intense pain. Patients with sacroiliitis are more severely incapacitated than patients suffering from disc-related low back pain.


  • Unilateral low back pain (on only one side of the body)
  • Pain extending or radiating to the hip and groin
  • Pain that runs down the side of the leg all the way to the ankle or even the foot, simulating sciatica from a herniated disc


The pain patterns of sacroiliitis are different from those of pain caused by a vertebral disc or facet joint. Patients may suffer from some all of the following problems:

  • Night pain: they are not able to sleep on the side that hurts
  • Pain when sitting: they are not able to sit on the side that hurts
  • Pain when standing: they always support all their body weight on the leg that doesn’t hurt
  • Pain when climbing stairs: they cannot climb stairs using the affected leg

Diagnosis of sacroiliitis

Given that there is no radiological test currently available that can show that the sacroiliac is affected or that the pain comes from there, the diagnosis of this condition is made through the patient’s medical history, a clinical examination, and a diagnostic injection.

As accepted by the worldwide scientific community, diagnosis of sacroiliitis must be made based on the following:

Patient’s medical history

The existence of a prior injury that might suggest possible sacroiliitis.

Typical symptoms

Mentioned above.

Physical examination

  • Positive Fortin sign: pain upon palpation of the sacroiliac joint.
  • Positive One leg stance test: pain when trying to bear weight on the affected side.

Maneuvers to check for joint pain (5 maneuvers)

  • Distraction
  • Compression  
  • Thigh Thrust
  • Gaenslen
  • Faber

When 3 or more of these maneuvers show a positive result (cause pain), and the clinical history and the physical examination suggest sacroiliitis, it is considered highly probable that the origin of the pain lies there.

The next step is to perform a single injection of local anesthetic into the joint. This procedure takes place in an operating room, under sedation and local anesthesia. 

If the pain remits by about 50% or more in the following hours, then and only then, can the patient be given a diagnosis of sacroiliitis.

Treatment of sacroiliitis

The treatment of sacroiliitis is radically different from the treatment of any low back pain that originates from the spinal column.

Conservative treatment

  • Specific physiotherapy to strengthen the musculature of the pelvis.
  • Pelvic belt or girdle.
  • Sacroiliac joint injection.
  • Radiofrequency or rhizolysis of the sacroiliac joint.

Surgical treatment

When conservative treatment is unsuccessful, there is the possibility of sacroiliac fusion surgery. Since the sacroiliac is a load-bearing or support joint, fusing this joint will not result in a loss of function or mobility for the patient. Keep reading to find out about this procedure. 

What is sacroiliac fusion surgery?

Fusion of the sacroiliac joint is an intervention that consists of stabilizing, fixing and eventually fusing the iliac bone to the sacrum, using titanium implants to join them.

What does it involve?

The operation consists of stabilizing, and fusing over time, the sacroiliac joint by  attaching three titanium pins horizontally across the bones.

At Instituto Clavel we perform this surgery with the IFUSE system, the technique that first made this surgery possible and the one that has been used in the greatest number of these surgeries around the world since 2008. It is the implant and the most scientifically proven technique, and the one with the surest guarantee of success.

Because it is a methodology in which the correct placement of the implants is fundamental, at Instituto Clavel we use the intraoperative navigation system O-ARM 2 to ensure this correct placement. We were pioneers in this technique in Spain.

The surgery is done under general anesthesia with the patient in a face-down position. Once the patient is sedated, we take a CAT scan using the O-ARM 2. A small, 3 cm cut is made in the side of the affected gluteus, and through this incision, using a system of narrow tubes to prevent damage to the adjacent muscles, the surgeon the penetrates the sacroiliac joint until reaching the sacrum bone to place the titanium implant.

Three implants are placed (small triangular rods) at the specific point indicated for that specific patient, in order to achieve improved stability of the joint and to guarantee that it will fuse over the coming months.

Recovery and rehabilitation after sacroiliac fusion surgery

The surgery takes about 1 hour and the patient will need to stay in the hospital for 48 hours. Since it is a surgery to stabilize the pelvis, the patient will need crutches to walk in order to partially take the weight off the operated side (they will be able to use the affected leg, but without putting full weight on it). Ten days after the surgery, we check to see how the surgical wound is healing, and the patient begins the specific rehabilitation treatment for this surgery.

Risks of sacroiliac fusion

Surgical risks

The specific risks of this surgery are the neurological risks (damaging the sciatic nerve). This is because the nerves that come together to form the sciatic nerve (the roots of L5 and S1), so an incorrect placement of the implants can damage the sciatic nerve. To avoid this type of complications, at Instituto Clavel we use the  O-Arm 2 intraoperative navigation system.

Postoperatory risks

Since the operation is performed through the gluteus muscles, following surgery there may be bruising in this area, which although it may be extensive, will disappear in a few days without causing any major problem.

Who are the doctors at Instituto Clavel who perform this surgery?

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