What is Sacroiliac Joint Pain?

SI Joint Pain

Your Sacroiliac Joints (SIJ) are a critical linkage system between your lower spine and pelvis. The sacrum (tailbone) connects on the right and left sides of the ilia (pelvic bones) to form your sacroiliac joints.

Your sacroiliac joints should be a fairly stiff or rigid link between the pelvic bones, and allow only a few degrees of movement. In some people due to trauma or just extra mobility, your sacroiliac joints have too much uncontrolled motion. This allows your sacroiliac joints to adopt an abnormal or stressed joint position, which may result in SIJ pain. 

When your sacroiliac joints are not moving normally due to either stiffness or excessive movement, it is referred to as Sacroiliac Joint Dysfunction, which normally results in sacroiliac pain.

It is vital that you have both normal SIJ movement and muscle control around this area to avoid SIJ pain and injury. 

Commonly sacroiliac dysfunction can cause lower back, hip, buttock and sciatic pain.

What Causes Sacroiliac Joint Pain?

There are two main groups of sacroiliac dysfunction that cause SIJ pain:

  1. Hypermobility / Instability 
  2. Hypomobility / Stiffness

Hypermobility issues are the most common and will be discussed further in this article.

Hypomobility is normally associated with pathologies that tend to stiffen your sacroiliac joints such as in Ankylosing Spondylitis.

What Causes Sacroiliac Joint Hypermobility?

Your sacroiliac joints should move a few degrees for normal movement. Like most joints, your surrounding muscles act to stabilise your sacroiliac joints during stressful or vulnerable positions. The most important sacroiliac stabilising muscles are your deep abdominal core muscles and your deep gluteal muscle groups.

Your core muscles: specifically the transversus abdominis and oblique abdominals through their attachments to the iliac bones help closure of the pelvis and improves the position, control and stability of the sacroiliac joints.

Researchers have discovered that contraction of the transversus abdominis muscle significantly stiffens and supports your sacroiliac joints. This improvement is larger than that caused by an abdominal bracing action using all the lateral abdominal muscles (Richardson etal 2002).

Further to this, researchers have discovered that your deep gluteal (buttock) muscles are important for controlling the lateral and rear aspects of the pelvis and hip. (Grimaldi et al).

When these muscle groups are weak or lack endurance your sacroiliac joints are vulnerable to excessive movement, which can lead to SIJ hypermobility dysfunction or instability and subsequent sacroiliac joint pain.

What are the Symptoms of Sacroiliac Joint Dysfunction?

  • Sacroiliac joint dysfunction can mimic numerous other back and hip injuries. 
  • Sacroiliac joint dysfunction can cause lower back, hip, groin, buttock and sciatic pain. 
  • Sacroiliac pain is typically worse with standing and walking and improved when lying down, but not always. 
  • It can sometimes be painful to sit cross legged and is normally painful to lie on your side for extend periods. 
  • Bending forward, stair climbing, hill climbing, and rising from a seated position can also provoke sacroiliac pain. 
  • Sacroiliac pain is  sometimes reported to increase during sexual intercourse and menstruation in women.

How is Sacroiliac Joint Pain Diagnosed?

Accurately diagnosing sacroiliac joint pain & dysfunction can be difficult because SIJ symptoms can mimic other common back conditions. These include other mechanical low back pain conditions like facet joint syndrome or a bulging disc.

X-rays are of minimal diagnostic benefit. MRI may show signs of sacroiliac joint inflammation or eliminate other potential pathologies. 

A thorough physical examination by your experienced musculoskeletal physiotherapist is the best method to assess for sacroiliac joint pain or instability.

This article originally appeared on physioworks.com.au and was written by John Miller


Consult with your Physician and / or Physiotherapist for a diagnosis and follow up with a Massage Therapist, Manual Osteopath, Acupuncturist, or Physical Therapist in conjunction with treatment plans.