My Sacroiliac joint keeps popping out!

Sounds bad, doesn’t it? But so many people come to me and say “My Sacroiliac joint keeps popping out!” Does it really?

In today’s article, we will look into the evidence around this subject. We will teach you some anatomy, how common pain arises from the Sacroiliac joint (SIJ), how much it moves, what happens to it during pregnancy and more. This isn’t going to be a complete guide to the Sacroiliac joint but we will touch on some areas as mentioned above.


So what is the Sacroiliac joint (SIJ)?


So the Sacroiliac joints are the joints in between the Sacrum and the Ilium on both sides. The joints connect the spine to the pelvis and they help to transfer loads to the lower limbs. The joints are large diarthrodial joints, which means a free moving joint with a cavity that is surrounded by a joint capsule called the synovium and it has fluid inside called synovial fluid (Cohen et al 2005).

On the sacral side of the joint, the cartilage on the surface is hyaline cartilage, which is made from type II collagen and is the weakest type of cartilage in the body. On the Iliac side of the joint, the cartilage on the surface is fibrocartilage, which is made from type I collagen and is the strongest type of cartilage in the body (Wong et al 2019).

The SIJ acts as a shock absorber for the spine as it transfers load into the lower limbs but it also works the other way transferring and converting torque from the lower extremities into the spine and upper body.

The movements at the Sacroiliac joint are:


Nutation is movement at the Sacroiliac joint, which occurs when the sacrum absorbs force. This force creates a downward, forward and anteriorly rotational movement of the Sacrum on the Ilium.


Counternutation is movement at the Sacroiliac joint, which occurs when the sacrum moves upward, backwards and posteriorly rotational movement of the Sacrum on the Ilium.


How much back pain is from the Sacroiliac joint (SIJ)?

Pain is quite common around the area of the Sacroiliac joints but this doesn’t necessarily mean that the pain is coming from the SIJ. In fact, just 15% – 30% of chronic, non-radicular lower back pain comes from the SIJ (Cohen et al 2013). So just because pain is at your Sacroiliac joint doesn’t mean that it is caused by it. So be careful to not make this assumption as pain can come from many sources and refer to this area. The amount of patients that I see at my clinics in Stoke on Trent that I have to try to explain this to is crazy!

How much back pain is from the sacroiliac joint

I can feel my SIJ move!

So can you really feel this or not?

You may believe that you can feel it but the chances are that you can’t. I think what a patient feels more often than not is a taut band of connective tissue tensioned by muscle spasm that effectively flicks over the area creating a clicky movement sensation and not a joint moving per se. There are loads of tests to palpate the movement of the SIJ to determine if it is stiff, but we know they are not that accurate now and probably have little use especially when you consider how much the Sacroiliac joint moves.


How much does the Sacroiliac Joint (SIJ) move?

Well, when I tell you will probably agree that you can’t really feel it move and it may be something else that you are feeling instead.


The SIJ only moves 2-3mm on average!

SIJ movement


So if you can feel 2-3 mm motion of a joint with your fingers through the skin, fat, fascia and ligaments then good luck to you but you may be wasting your time. Likewise, it is unlikely that you will feel this movement on yourself in general either. For example, when I walk, my SIJ is going through these 2-3 mm of motion but I am absolutely oblivious to it!


Yes but that’s an average movement but to what extent can it move?


It was found that the most movement in the SIJ was 8mm in normal individuals, which is more than 2-3 mm but still not that much (Goode et al 2008). Now, it is likely to move more in certain hypermobility conditions, such as Ehlers-Danlos syndrome, but this condition is quite rare affecting between 1 in 5000 and 1 in 25,000 people (Enix et al 2019).


Does it move more in pregnancy though?

The short answer is yes.

SIJ pain in pregnancy

But does this extra movement cause pain in pregnancy?

SIJ laxity does exist in pregnancy but when they looked at whether this laxity correlated with pain, they found that the same laxity was found in moderate and severe pain when compared to mild to no pain (Damen et al 2001). So laxity doesn’t appear to be the reason but people do feel better when they wear an SIJ belt so surely this rebukes this idea? Well as always this is debatable. Clearly, the movement can hurt but is this due to sensitisation of the joint making any movement hurt irrespective of its amount? It’s hard to know but based on the evidence it’s more likely.


So if pain on movement hurts then what muscles should you train if any?

Now as previously discussed the joint doesn’t move much and has lots of ligament support so the question is, does the Sacroiliac joint (SIJ) rely on muscles to stabilise it or is it stable enough on its own?

In a study with 15 female volunteers, aged 15–30 years who were in good physical health with no recent complaints of spine, pelvis or hip problems, they tested the stability of the SIJ using Colour Doppler Imaging (CDI) with excitation of the pelvis by means of an oscillation device. They had the participant contract various muscles with EMG to check that muscles activation level and compared this to the relaxed state confirmed on EMG.

So what did they find?

They had better stiffness and stability with muscle contraction compared to relaxed and this was particularly the of the following muscles:

Erector Spinae (back extensors)

Biceps Femoris (Hamstring muscle)

Gluteus Maximus

So it would seem that these are important for SIJ stability but they were lying down in this study but standing may be more stable even without the muscle contractions in fact, this is very likely and therefore maybe the muscles don’t matter so much?

(van Wingerden et al 2004)


Why does it hurt then if it’s not laxity related?

The likely suspect is sensitisation of the area as when you are pregnant your body is in more of a protective mode, especially for that area of your body and so the pelvis is more likely to be sensitive and overprotective making it easy to upset and irritate. We already know this can occur in almost any injury too so why would this be different.


How do you de-sensitise the Sacroiliac joint (SIJ) then?

Yes, contrary to popular belief the classic Sacroiliac joint manipulations can help to de-sensitise the area but they don’t actually change the joint position (as seen below). The effect is much more neurological than mechanical. But this isn’t the only way to desensitise the area and probably not a long term solution either!

Can you change the Sacroiliac joint (SIJ) joint position with manipulations?



As usual, this is the best way to affect changes with Sacroiliac joint pain and although you will improve muscle function it is more about developing load and movement tolerance. I have discussed this concept in more depth in another article:

What is the difference between injury rehab and normal training?

The concept is to start with easier movements with lower loads and work them within your tolerance and as your tolerance improves then you progress the exercises with movement and load. As an example of this see below:

Bridging is low load and is a symmetrical movement so may be a starting point for some people.


Next, you could move onto a single leg bridge that increases the load and is creates an asymmetrical load:


Moving into greater loads with symmetry you could do basic squats:


And an advancement could be a Bulgarian Split Squat for example:


Remember exercises need to be tailored to you, your tolerance and your ability, so these are just for demonstration purposes to give you the principle ideas behind the rehab of the Sacroiliac joint. At Hawkes Physiotherapy we can assess you and tailor a treatment plan to be specific to your problem and needs and we have clinics in Talke and Stoke.



So there you have it, your Sacroiliac joint does move but not much and it’s not popping out for sure. It can cause pain but not as much as some people believe and it does move more in pregnancy but it is not the laxity per se that causes the pain. Muscles can be trained to ‘stabilise’ it but this may not be the most important feature, in fact, building tolerance to movement and load is the key through exercise and yes you can perform SIJ manipulations to affect this too.


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If you need any further information or would like to book an appointment then call Hawkes Physiotherapy on 01782 771861 or 07866 195914.

  • Cohen S., Steven P., Sacroiliac joint pain: a comprehensive review of anatomy, diagnosis and treatment, IARS, November 2005, volume 101, issue 5, pp 1440-1453 (LOE 3A)
  • Cohen, Steven P., Yian Chen, and Nathan J. Neufeld. “Sacroiliac joint pain: a comprehensive review of epidemiology, diagnosis and treatment.” Expert review of neurotherapeutics 13.1 (2013): 99-116.
  • Damen, Léonie, et al. “Pelvic pain during pregnancy is associated with asymmetric laxity of the sacroiliac joints.” Acta Obstetricia et Gynecologica Scandinavica: ORIGINAL ARTICLE 80.11 (2001): 1019-1024.
  • Enix, Dennis E., and John M. Mayer. “Sacroiliac Joint Hypermobility Biomechanics and What it Means for Health Care Providers and Patients.” PM&R 11 (2019): S32-S39.
  • Goode, Adam, et al. “Three-dimensional movements of the sacroiliac joint: a systematic review of the literature and assessment of clinical utility.” Journal of Manual & Manipulative Therapy 16.1 (2008): 25-38.
  • van Wingerden, Jean-Paul, et al. “Stabilization of the sacroiliac joint in vivo: verification of muscular contribution to force closure of the pelvis.” European Spine Journal 13.3 (2004): 199-205.
  • Wong, Michael, and John Kiel. “Anatomy, Abdomen and Pelvis, Sacroiliac Joint.” StatPearls [Internet]. StatPearls Publishing, 2019.

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