What is motion palpation:
It’s common for therapists to believe they can palpate the amount and quality of movement between individual spinal segments and in the sacroiliac joint. The movements being palpated are minute, usually just a few degrees. Numerous factors could affect the sensitivity of the tester, including the facts that these movements are evaluated through rather thick skin and being resisted by muscle forces. These methods are taught worldwide, and the knowledge and skill the student possesses on these techniques is examined and graded. This is done without any objective criteria to evaluate if the teacher has a superior skill or sensitivity (this is merely assumed), or if these techniques have merit at all.
Studies (0) have examined how well a bunch of people are able to agree with a „palpation guru“, or just the ability of a group of people to have a reasonable degree of agreement (it’s known as inter rater reliability), or even if a person can just simply agree with themselves (intra rater reliability).
The whole gig is akin to an inition ceremony, like two blind men discussing the color of the emperors new clothes. To graduate, you must of course guess the same color as the teacher. It sounds far fetched, but the idea is attractive and has some face value. It’s also the source of many a legend in the physical therapy profession – everyone has heard of these therapists with fingers that are like eyes that can see into the body and feel every knot, twist, limitation, microscar, and blood flow restriction under the sun. Painscience has a nice article on how easily human senses can be tricked by beliefs and expectations.
However, at the end of the day what matters is if the method is valid. Validity is assessed by how well a method or test performs against some objective standard. I’d prefer to only look at studies where the judgement of a palpating therapist is tested against an objective criteria, such as ultrasound, x-ray imaging, MRI or compatible techniques – but there aren’t too many of these, so when lacking direct evidence I’ll discuss some indirect evidence instead.
It’s difficult to accurately palpate the location of bony landmarks around the sacro-iliac joint, the precision is about 20 mm (1), and that’s without trying to track movement as well. To put that number in context, the movement of the sacro-iliac joint is between 1,2° and 4.5°, with a high degree of variability between individuals (2) – less than 10 mm of motion, and so way outside the accuracy of palpating bony landmarks. Somewhat similar to hearing a whisper from another room where music is being played. Also indicated by (2) the difference between problematic and non-problematic sacro-iliac joints is more likely in the pattern, not amount, of movement.
Given this, it’s hardly surprising that clinical palpation and motion testing of the position of the sacro-iliac joint is positive before and negative after a manipulation – even though no changes occur in the sacro-iliac joints themselves (3). This is why researchers should blind examiners – for a motion palpation difference to be plausible, the motion increase of the sacro-iliac joint would have to be way outside the physiological range of motion. So a study to demonstrate this would have to be very robust.
Palpaters have difficulties locating the correct spinal segment, being successful in only 50% af attempts (4). That makes it unsurprising that the agreement between different raters of lumbar spine segmental mobility is not high, although each rater is fairly consistent (5). Similar findings for assessing the rotatory mobility of spinal segments (6).
There are unfortunately few studies that objectively evaluate motion palpation in the lumbar spine against an objective measurement. The only study close to it used ultrasound to evaluate lumbar segmental rotation based on the depth of the transverse process from the skin (7). The results demonstrated that the examination technique and the ultrasound examination agreed on a dysfunction of a spinal segment. Unfortunately, only the „dysfunctional“ spinal segment was evaluated, the change of depth from a treatment that was provided was around 0.5 mm, and everyone was rotated towards the left. As a result, it’s impossible to say if it’s the diagnostic technique that’s valid or that everyone is just rotated a little bit towards the left (maybe because they are all right-handed). The study design, unfortunately, just can’t answer that question*.
If one is looking for a reason to manipulate a spine, there’s no need to perform any of these palpatory techniques. Studies have looked at when a lumbar spinal manipulation is most useful; pain has been present less than 16 days, no symptoms below the knee, hip mobility is good, and the spinal gross range of motion is limited (8).
Palpating the location of the uppermost cervical segment is actually pretty accurate (9), so that’s already better than the rest of the spine. However, therapists apparently can’t identify segments with differing mobility, and even though mobility is increased acrosst he board by cervical spinal manipulations, there was no connection between mobility changes and the clinical outcome of treatments (10).
There is one way to increase the validity and accuracy of certical spine motion palpation and manipulation: slice away the skin and muscles first (11)! Good luck selling that to patients. Unlike the lumbar spine, there are no clinical indications to predict when manipulations are useful (12).
Compared to how extensively used and taught these motion palpations are, the research on their validity is certainly lagging far behind. However, the research is fairly homogenous: motion palpation is inaccurate and lacks validity, and the results of such palpations are entirely unrelated to clinical outcomes. The motions being palpated are simply too small, and there is too much interference from other tissues for these tests to even be humanly possible.
But no reason to panic, even though motion palpation is outdated there’s plenty of other methods out there that are supported by the evidence.
- For those interested in research designs, the study has various flaws. There was no way to confirm the clinical palpation was changed by the treatment, because everyone received manipulations and only one rater was used. There was no control group, and no blinding – the study was only a pilot study (although no follow-up is yet published), meaning it was meant to generate ideas for better research later. A small flawed pilot study that goes against the majority of other studies should not guide clinical practice.