Over the 30 plus years I have been working as a musculoskeletal Physiotherapist, I have lost count of the number of patients who I have seen, with what they describe as an “unstable pelvis”. These patients may have come to see me with back, pelvis or leg pain and they have typically had their problem for a number of months or years. By this time, the patient has usually seen a number of other healthcare professionals. All of these clinicians will have given their opinion as to the cause of the patients pain. This is where the diagnosis of an “unstable pelvis” has come from, often with the advice that a sacro-iliac joint has “come out of place”.

The tests that have been used to come to these conclusions of pelvic joint laxity and of misaligned sacroiliac joints, involve locating parts of the pelvis, both visually and by touching them. The clinician then detects movements of the pelvic bones during specific test movements and then decides if there is too much or too little mobility. However, there is on average only 2 or 3 degrees of movement in the sacro-iliac joints of most people, so even in the hands of the most skilled practitioner, it is impossible to feel and measure such small ranges of movement.

Another popular test for pelvic instability, is the “active straight leg raise test”. This involves the patient lying flat on their back and then lifting a leg off the treatment couch. An inability to do this, or being able to do the movement with difficulty, may then be used to indicate pelvic joint instability. If the clinician then applies a stabilising pressure through the pelvis with their hands and the leg lifting is easier, this is regarded as confirmation of a pelvic instability issue. Again the evidence for this is not good and research has shown that simply having pain in the back or pelvic area will lead to a “positive” test.

The truth of the matter is that the tests and procedures that are used to decide if the pelvic joints are unstable, have no broad scientific validity. There is plenty of compelling evidence that shows these popular clinical tests to be unreliable & inaccurate. So how come so many highly skilled practitioners have been diagnosing unstable pelvic joints for so long? Well, the tests themselves were never based on any sound science. They were simply made up by practitioners, who sincerely believed that they could actually see & feel the movements that they then interpreted as being extremes of movement. It’s a bit like the story of the Emperors new clothes. If you believe hard enough you will see it! Its simply a trick of the mind. This has been termed “pareidolia”, which is a psychological phenomenon where a vague stimulus is perceived as being of significance. Pareidolia is used to explain the reason why people see familiar shapes such as faces or animals in cloud formations or even a sacred image in a slice of toast.

For a patient with the painful back or pelvis, this kind of neural mix up can be extremely unhelpful. Being told that a key part of your anatomy is unstable or out of place, results in worry and anxiety. This can lead to hyper vigilance and fear avoidance and the adoption of movement strategies that actually provoke rather than alleviate the pain. A common example of this is the patient who dutifully exercises their core muscles in an attempt to stabilise their supposed unstable pelvis. They also pull in their stomachs and brace whenever they move and bend, in an attempt to protect their pelvic joints, which they believe are vulnerable and likely to “pop out”. The irony here is that these precautionary tactics actually stress the pelvis and can perpetuate and worsen the pain.

So, to answer the question of whether or not a pelvis can become unstable, the answer is yes – but not very often. Any joint in the body can become too loose or as the medical profession terms it “unstable”. This can happen as a consequence of either a significant forceful injury, repetitive low grade stress over a long period of time, genetic issues or combinations of these factors. However, we should acknowledge that the pelvic joints are extremely strong structures. The sacro-iliac joints are supported by incredibly strong ligaments and the joint surfaces are shaped in such a way as to make them inherently stable. It takes an immense amount of force to damage these structures to the point where instability results. Certainly far more force than is applied to the pelvis during daily activities or even the hardest sporting activity.

In my 30 plus years of clinical practice I have come across literally a handful of people who have had true pelvic instability. These individuals were injured in car accidents, where pelvic fractures occurred and in one case by a horse that reared and landed on its back with the unfortunate rider still astride the upturned creature.

Many patients with the diagnosis of “pelvic instability” have sadly, in my opinion, been left to worry over something that is highly unlikely to be true and possibly given remedial exercises which may actually make their pain problem worse.

In my next blog I’ll discuss our approach to dealing with sacro-iliac / pelvic pain.

References

Good A, Heqedus EJ, Sizer P, Brismee J-M, Linberg A, Cook CE
“Three-Dimensional Movements of the Sacroiliac Joint: A Systematic Review of the Literature and Assessment of Clinical Utility”. J Man Manip Ther 2008;16(2):113-7

Holmgren, Waling
“Inter-examiner reliability of four static palpation tests used for assessing pelvic dysfunction”. Man Ther. 2008 Feb;13(1):50-6. Epub 2007 Jan 8

McGrath MC
“Palpation of the sacroiliac joint: An anatomical and sensory challenge”. IJOM September 2006 Volume 9, Issue 3, 103–107

Palsson TS, Hirata RP, Graven-Nielsen T
“Experimental Pelvic Pain Impairs the Performance During the Active Straight Leg Raise Test and Causes Excessive Muscle Stabilization”. Clin J Pain 2014 Aug 12

Preece SJ, Willan P, Nester CJ Graham-Smith P, Herrington L, Bowker P
“Variation in pelvic morphology may prevent the identification of anterior pelvic tilt”. Phys Ther 2002 Aug;82(8):772-81

Riddle DL, Freburger JK
“Evaluation of the presence of sacroiliac joint region dysfunction using a combination of tests: a multicenter intertester reliability study”. Phys Ther 2002 Aug;82(8):772-81