What is Sacroiliac Joint Pain?


What is the sacroiliac joint?

The sacroiliac (SI) joint is an anatomical structure connecting the sacrum (more commonly known as the tailbone) to either side of the pelvic bones, known as the innominate. The joint is small and strong with the sacrum tightly wedged between the pelvis and is supported by ligaments and surrounding muscles. These muscles are some of the strongest and largest in the body, designed to provide joint stability and limit mobility in the area. It is essential for the transmission of load between the spine and lower extremities both in static positions (e.g standing upright) and during movement. Given its important role in load distribution, it has little to no motion and its primary function is shock absorption.

SI joint pain can be loosely classified into three categories; pregnancy-related si pain, specific pathologies of the SI joint (including inflammatory conditions or fractures), and nonspecific si pain, where the origin of the pain is unknown.

Symptoms of SI dysfunction

Given the close proximity to the low back (lumbar spine), pelvis, and hip, SIJ pain can present in many different locations and forms. Some common symptoms of SI dysfunction include:

  • Low back, hip, groin, buttock pain
  • Pain that radiates down the back of the leg
  • Pain typically is worsened when standing or walking and improves when lying down on your back
  • Pain is progressive in nature with fluctuations depending on aggravating daily activities
  • Pain when sitting cross-legged
  • Pain when lying on your side for prolonged periods, especially when lying on your side in bed
  • Pain when climbing stairs or hills
  • Pain when standing on one leg (e.g getting into and out of the car)
  • Pain when moving from a seated position to standing

SI Dysfunction and Low Back Pain

In a study conducted by the Global Burden of Disease, low back pain was reported as the highest cause of years lived in disability in Australia and around the world, with 1in 6 Australians suffering from low back pain. SI dysfunction is often an overlooked cause of chronic low back pain. Research estimates that SI dysfunction is responsible for 15-30% of patients with chronic low back pain. The physiological modifications during pregnancy is another significant contributor to both SI and low back pain. Two-thirds of women report pregnancy-related low back pain as a result of the postural adaptations for the growth of the fetus.

Mechanisms of pain include either too much movement in the joints (hypermobility) or too little movement (hypomobility), compression or shearing forces, repetitive axial loading, sudden rotation, falling directly onto the tailbone, sporting collisions, or motor vehicle accidents. Additional sources of pain include micro or macro fractures, surrounding soft tissue injuries, arthritis, and inflammatory conditions.

Ankylosing Spondylitis

Ankylosing Spondylitis, or AS, is another common cause of SI pain. AS is a chronic, autoimmune, inflammatory arthritis that commonly involves the si joints, spine, and the surrounding soft tissue structures. Literature shows that males account for the majority of AS cases and is often diagnosed following an insidious onset of immobility and stiffness in the back.

Similar to many autoimmune inflammatory conditions, the precise cause of the AS is currently unknown. However, it is believed to develop due to an interaction between an individual’s genetic makeup and external environmental factors. AS can cause bony changes between the tailbone, lumbar spine and pelvic bones, joint space widening, and over time may progress to the fusion of the surrounding bones. These changes can be viewed on X-ray which can be used to monitor the long-term progression of the disease by assessing the rate of structural change.

Currently, there are no disease-modifying treatments available as the exact cause is unknown, however prescription anti-inflammatory medications are commonly used. Following assessment and diagnosis by health professionals, the practitioners at Beyond can help improve and maintain spinal flexibility, assess posture, relieve compensatory changes in the body, and decrease functional limitations.

Risk factors to SI Dysfunction

Increasing age has been correlated with si dysfunction due to the adaptive changes to the bony surface of the tailbone and pelvic bones and supporting connective tissue, especially the ligaments. This can progress to arthritis and may trigger an inflammatory response by the body. With increasing age the movement available to the area is near non-existent, often leading to compensatory biomechanical changes above and below the region.

Leg length discrepancy can contribute to si dysfunction and pain. Uneven leg lengths lead to a mechanical malalignment and weight imbalance causing uneven load distribution on either side of the pelvis. Abnormal gait cycles and changes to weight-bearing can also have a similar effect and predispose to pain. Additional risk factors include scoliosis, trauma, lumbar fusion surgery, obesity, pregnancy, activities that involve repetitive lifting, prolonged sitting, and poorly conditioned low back and hip muscles.

Females and SI Dysfunction

The shape of the SI joint differs greatly between males and females. The wider shape of the female pelvis and decreased surface area increases the stress and load inflicted on the region leading to ligament strain and increased risk of dysfunction.

Pregnancy-related hormone changes further exacerbate the risk of SI dysfunction by causing ligament laxity and increased mobility in preparation for birth. These changes can further lead to an increase in pressure and stress on the pelvic floor, a sling-like muscular structure sitting at the base of the two pelvic bones holding the reproductive organs that sit above. Acting together with deep internal core muscles helps support the integrity of the low back and pelvis by functioning like a corset around the area.

During this period of increased instability and ligament changes, clinical pilates can help support and stabilize the area as well as helping surrounding structures. The Beyond Birth Post Natal Program is a self-paced program that can be completed in the comfort of your own home to further support the body as it recovers from the physical demands of pregnancy and childbirth and helps mothers reconnect with their bodies.

Myth Busting the SI Joint

One of the most common assumptions regarding the SI joint is that it can become unstable and out of place. Given the bony architecture of the region and that the tailbone is tightly sandwiched and supported by several strong ligaments, the range of motion available is typically in the range of 1-2 degrees, and near non-existent in older individuals. This degree of movement emphasizes its stability and is therefore very difficult to move out of place, requiring significant trauma or childbirth, because of this we avoid diagnosing si instability.

How can SI joint dysfunctions be treated?
















SI joint pain can be tricky to diagnose as the quality and location of the pain can mimic that of low back or hip pain. The osteopaths and physiotherapists at Beyond use specific orthopedic tests to identify SI joint dysfunction and differentiate it from low back, hip, or groin pain. Our manual practitioners will then use different techniques, such as soft tissue, articulation, taping (rigid or k-tape), manipulation, and muscle activation against resistance to treat the dysfunction. Having a hole body approach in mind, the practitioners at beyond will address and treat surrounding joints that may be compensating including the low back and hip and muscular tightness that may have manifested and contributed to the pain.

Our myotherapists can target and relax the muscles that are overworked and compensating for the si dysfunction with soft and deep tissue massage techniques alongside dry needling. They also provide advice for relief at home as well as stretching and mobility exercises.

The exercise physiologists at Beyond can work with patients to strengthen and support the muscles surrounding the joint. They will conduct a comprehensive movement assessment of the area and whole body, identifying any areas of weakness that may be contributing to the pain. Using this information, they will create an individualized strengthening program and work with you to ensure you are executing this in a safe and correct manner and guiding you through progressions as you start to get stronger.

Alongside manual therapy, we provide extensive health information and prescribe individualized management plans to help meet your treatment goals and prevent future injuries. Management can include; strengthening exercises, mobility, and a multi-disciplinary approach including exercise physiology and clinical pilates.

Beyond’s Top Tips

Have you recently been diagnosed with a si dysfunction or suspect one? Here are Beyond’s top tips:

  • Activity modification: Avoid aggravating activities (e.g single-leg weight bearing when getting in and out of the car)
  • Avoid periods of prolonged sitting and standing (we do not recommend bed rest)
  • Try sleeping on your unaffected side with a pillow between your knees
  • Heat pack: try rest a heat pack across the lowest part of your back when sitting
  • See your pharmacist for anti-inflammatory and pain relief medication advice
  • Physical Therapy: Stay mobile by completing some gentle movement and stretching (see below)

Our Favourite Take Home Exercises

Pelvic tilts

Bent knee dropouts

Lumbar rotations

Knee hugs

Dead bugs


Glutes Release Spikey Ball

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