Sacroiliac joint pain is an under-recognised cause of buttock or groin pain. Generally, treatment consists of exercise therapy and activity modification. However, not all cases settle with simple treatments, so injections are needed. When and how for a sacroiliac joint injection?

What is the sacroiliac joint? 

sacroiliac joint pain

The sacroiliac joints are between the sacrum (below the lumbar spine) and the pelvic bones. Essentially, they provide shock absorption and transfer load from the lower body to the upper body.

Causes of sacroiliac joint pain  

Usually, repetitive trauma or force on the sacroiliac joint can come from activities such as running. However, other triggering factors include a direct fall onto the sacroiliac joint, an autoimmune disorder that attacks the sacroiliac joint (sacroiliitis), or pregnancy.

Diagnosis of sacroiliac joint pain

In general, the diagnosis of sacroiliac joint pain is tricky. Firstly, symptoms overlap with other causes, such as a herniated disc in the spine or hip arthritis. Moreover, special tests for sacroiliac joint pain are not a slam-dunk for this condition. Finally, imaging is often normal despite actual SI joint pain being present.

MRI helps exclude a condition known as sacroiliitis, an immune system problem causing sacroiliac joint inflammation. Sometimes, an MRI can rule out pain from the lumbar spine (Sciatica) or pelvis (hamstring origin tendinopathy).

A few experts think an image-guided sacroiliac joint injection is the best test for SI joint pain. For example, if a person experiences a 75% decrease in pain after injection, we can be more sure that the pain is from the joint.

Treatment, including sacroiliac joint injection

glute bridges

Generally, we recommend simple treatments first. Physiotherapy consists of strengthening, mobility exercises, and soft tissue therapy helps. Moreover, a brace to support the joint can be helpful, particularly during pregnancy. Anti-inflammatory tablets such as ibuprofen can settle pain as well.

If sacroiliac joint pain persists, we consider a sacroiliac joint injection.

Rarely do we ever consider surgery, if at all.

More about sacroiliac joint injection

We consider a cortisone injection for the sacroiliac joint to treat inflammation and pain. However, the sacroiliac joint is deep and narrow, so we need imaging to get the cortisone into the right spot.

More recently, we have started to use platelet-rich plasma for exceptional cases of sacroiliac joint pain. For example, people with hypermobility or a history of trauma can suffer from sacroiliac joint dysfunction. They may benefit from 1-2 PRP injections to aid in the healing of ligaments and the joint.

Traditionally, we use expensive X-rays with a dye for a sacroiliac joint injection. However, more recently, many doctors have been using ultrasound. Using ultrasound has many advantages, including a lack of radiation and less cost. Moreover, recent studies suggest that the accuracy is similar whether you utilise an X-ray or ultrasound.

Sometimes, a sacroiliac joint injection is combined with a piriformis injection, especially with mixed signs.

Frequently asked questions about sacroiliac joints 

Sacroiliac joint pain and pregnancy: is it common?

Yes, SI joint pain is more common during and after pregnancy. Overall, we think that hormone changes during pregnancy play a role in pain in this joint. Treatment principles are similar to rehab +/- an injection.

Do I need an X-ray or MRI before injection for the sacroiliac joint?

Generally yes. Pain in the sacroiliac joint area can be due to other causes, such as nerve pinching from the lumbar spine or pelvic problems, such as endometriosis or ovarian cysts. Overall, we think an MRI should be done to ensure your pain is not coming from other structures.

Why are sacroiliac joint injections so expensive? 

Overall, it depends on how your doctor does the injection. If the injection is done by X-ray, the costs can be high due to the hospital room, nursing staff, and X-ray equipment cost. However, if the injection is done under ultrasound, the costs are usually much lower because the injection is usually done in a clean office environment without expensive extra equipment. Also, we know that the accuracy of ultrasound-guided injection is similar to that of X-ray-guided.

I’ve been told that SI joint injections should only be done with X-rays, not ultrasounds. Is this right? 

We don’t believe so. Ultrasound-guided SI joint injections are safe, accurate and less expensive than X-ray-guided injections. Moreover, you are not exposed to harmful and unnecessary radiation.

Are you sedated for a SI joint injection? 

Generally, no if using ultrasound guidance. However, we use a local anaesthetic to numb the area before injecting cortisone or PRP.

Do SI joint injections cause weight gain? 

While cortisone injections have side effects, we know that intermittent injections do not cause weight gain

How long do SI joint injections last?

The effect of an SI joint injection depends on the injectable used and the severity of the pathology in the SI joint. Generally, we expect a cortisone injection to last a few months and a PRP injection to stay longer. 

Psoriatic arthritis and SI joint: How can you tell it is psoriatic arthritis vs osteoarthritis? 

Both inflammatory arthritis and osteoarthritis can affect the SI joint. However, the treatment of both conditions is different. Inflammatory arthritis consists of autoimmune diseases that attack certain joints, such as the SI joint. Examples of inflammatory arthritis include psoriatic arthritis and rheumatoid arthritis. 

Generally, we use MRI to help us with the exact diagnosis. In inflammatory arthritis, we see inflammation of the middle of the joint with erosions of the joint. 

Final word from Sportdoctorlondon

Sacroiliac joint pain is a common and under-reported cause of buttock pain. You should see a doctor who can diagnose and manage SI joint pain. Ultrasound-guided SI joint injections are as good as traditional X-ray-guided injections (but are at least half the price). Sometimes,  a sacroiliac joint injection is combined with a piriformis injection to get better results.

Related conditions:

Dr Masci is a specialist sports doctor in London. 

He specialises in muscle, tendon and joint injuries.