Sacroiliac Joint Pain, Pelvic Instability and Pelvic Girdle Pain

Sacroiliac joint pain, pelvic instability and pelvic girdle pain – what are these structures?

Sacroiliac joint pain, pelvic instability, and pelvic girdle pain are terms that may have been used in the diagnosis of your condition.  But what do these terms mean and what structures are they talking about?

SIJ pain can occur at the SIJ anatomy of the pelvis from the back
SIJ pain can occur at the SIJ. Anatomy of the pelvis from the back

Sacroiliac Joint Pain:

The sacroiliac joints (sometimes abbreviated to SIJs or SI joints) are the joints at the back of the pelvis, formed between the two bony wings of the pelvis and the tailbone (sacrum) – see the images above.

  • These joints are designed for stability with extremely little movement capacity. They are flat or “plane” joints though the surfaces of the joint are not completely flat. They are irregular or bumpy to allow some interlocking of the bones for the stability they need.  
  • They are also surrounded by some of the strongest ligaments in the body. This stable joint structure allows transfer of large forces between the body and the legs during walking, running and jumping.  
  • Some movement occurs in these joints during walking and running, where one leg is moving forward and the other backward, resulting in a small amount of joint rotation.  
  • Movement at the sacroiliac joints will also occur during extremes of hip or back motion, although most scientists agree that the amount of movement that occurs at the sacroiliac joints is very small. 

The Pubic Symphysis

The other joint that completes the pelvic ring is the Pubic Symphysis. You can read more about the pubic symphysis here.

SIJ pain can occur at the SIJ anatomy of the pelvis from the front
SIJ pain can occur at the SIJ. Anatomy of the pelvis from the front

Sacroiliac Joint Pain 

Pain and functional difficulties related to the sacroiliac joint: 

  • most commonly develop during pregnancy or childbirth 
  • may occur after a major trauma, such as a hard fall onto the bottom or a large force through one leg, for example being dragged by one leg after a fall from a horse or water-skis.  
  • may develop over time, related to certain types of repetitive forces.  
  • can develop when there is a problem with the lower back or hip joints, transferring extra load across the sacroiliac joint.  
woman with buttock pain maybe SIJ pain

Pelvic Instability

Sacroiliac pain and dysfunction are however, greatly over-diagnosed. While true instability does occur, it is relatively rare and there are many people living unnecessarily in fear, related to a diagnosis of ‘pelvic instability’ or being told their pelvis keeps moving ‘out of place’. 

Here are a few facts about the sacroiliac joint that may dispel some of this fear: 

  • The structure of the sacroiliac joint makes it a very stable joint 
  • Asymmetry in the human body is normal 
  • Differences in tightness of the muscles that join on to either side of the pelvis occur naturally, related to leg or arm dominance, sport and occupation. This asymmetry may cause an appearance of asymmetry in the resting position and movement of the pelvis. This is normal and has not been linked to harm. 
  • Differences in leg length of up to around 1cm are common and normal. Leg length difference may also produce an appearance of asymmetry in pelvic position in standing.  
  • A click occurring in a joint does not mean it has moved ‘in or out of position’. All of us click and pop, some just a little more than others. These are usually normal joint or tendon sounds.  
pelvic instability and hypermobility

Other Causes of Sacroiliac Joint Pain

There are also causes for sacroiliac joint pain that are related to other general health conditions. Sacroiliitis refers to an inflammation of the sacroiliac joints associated with a systemic inflammatory disease such as Ankylosing Spondylitis. You can read more about non-musculoskeletal causes of hip and pelvic pain here. 

Pelvic Girdle Pain

Pain related to the sacroiliac joints is most commonly experienced in the upper buttock region, usually right over the joint, in the area of the dimples at the top of the buttocks. As the pelvis is a ring joined at the front by the pubic symphysis, problems with the sacroiliac joints are sometimes associated with pain in the pubic symphysis – groin region. This is then referred to as Pelvic Girdle PainThere are many other causes for buttock and groin pain, however, so visit our Pain Locator Map to read about different factors that may be related to pain in each of these regions. 

sacroiliac joint pain, pelvic instability and pelvic girdle pain

Always seek out a health professional with experience and up-to-date knowledge in this area. Visit our directory to find a Hip Pain Professional near you.

Need Help? How Can A Hip Pain Professional Help?

Your Hip Pain Professional will be able to assess your sacroiliac joints to determine if they are likely to be the cause of your pain. If you have sacroiliac joint related pain, you may require:  

    • advice on modifications to activities or positions – e.g. workplace set-up  
    • an exercise program to provide optimal muscle support around the joints 
    • advice regarding short term bracing or taping – only appropriate for short term use and usually only for severe pain and during late stage pregnancy or after trauma 
    • an injection for short term relief of severe pain, while you work on your rehabilitation.

Search For A Hip Pain Professional Here.

hip pain professional helping with SIJ pain or pelvic pain.

Meet our Hip Pain Professionals – Health professionals that know hips

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This blog was written by Dr. Alison Grimaldi, with contribution from one of our Hip Pain Professionals, Kirsty McNab, experienced physiotherapist.

Dr. Alison Grimaldi is a globally recognised expert physiotherapist, researcher, and educator, who has over 30 years professional clinical experience helping patients recover from a wide range of hip and pelvic conditions.

Dr Alison Grimaldi - Hip Pain Professional

Dr. Alison Grimaldi  BPhty, MPhty(Sports), PhD, FACP 

Dr Grimaldi has completed Bachelor of Physiotherapy, Master of Physiotherapy and  Doctor of Philosophy (Physiotherapy) degrees. She is a fellow of the Australian College of Physiotherapists, Practice Principal of PhysioTec Physiotherapy, an Australian Sports Physiotherapist , an Adjunct Senior Research Fellow at the University of Queensland, as well as an author and global educator. Her passion is helping people with hip pain, and educating other health professionals around how to help more people with hip pain.

Check Out More You Can Read on this Area at HipPainHelp:

  1. What is Proximal Hamstring Tendinopathy – A Pain in the Butt: Learn what this condition is (also known as high hamstring tendinopathy), and learn what are the causes and symptoms?
  2. Upper Buttock Pain  learn about structures in and around the upper buttock region that may be involved in pain in this region
  3. Causes of Lower Buttock Pain learn about structures in and around the upper buttock region that may be involved in pain in this region
  4. Hip Related Sciatica (piriformis syndrome, deep gluteal syndrome): what, where, and how? Read more about possible causes of pain higher in the buttock muscles
  5. Top Tips for Hip Pain Relief Sitting, when Socialising or Travelling.  If your nerve pain is exacerbated when sitting this blog may be extremely useful in suggesting ideas to help relieve this.

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