The best clinical tests for hip abductor muscle dysfunction

Hi All,

Welcome to tendinopathy blog 5. The core mission of this blog is to improve the clinical knowledge and skills of busy clinicians by discussing research and how it fits into clinical practice. I like the analogy of ‘joining the dots’, because I am sure that like me, many clinicians feel they would love to have a good grasp of all the information out there and how it can make them a better clinician. Ahh, if only there were more hours in the day!

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As you know the usual format is discussing new research, but this week there is no really juicy clinically relevant research, so instead we will have a clinical update on – The best clinical tests for hip abductor muscle dysfunction ....

Hope you enjoy...

Hip abductor muscle dysfunction may be a feature of abductor tendinopathy (Allison 2015-see blog 2/2016). It is important to assess hip abductor motor function thoroughly as what you find will influence rehab. Here is a brief review of some useful clinical tests.

1) Sidelying straight leg raise – useful for assessing gluteus medius (Gmed) activation vs synergists (eg. TFL), movement preferences/patterns, as well as endurance. A classic test. Not going to discuss in detail as it is a very commonly used one.

2) Maximal voluntary isometric contraction (MVIC) of hip abduction in inner vs outer range. Really important to assess different ranges to be able to identify poor inner range abductor function – more on this below. Use a dynamometer preferably - check out Kristian Thorborg’s paper on hip maximal isometric contraction testing for a reliable method using a hand held dynamometer. I would advise practice a lot and test your own reliability in the clinic in a handful of patients to become more confident. What is an acceptable result in kg of force is really dependent on your technique and the person you are testing – could be anywhere between 10-35kg – again practice is the key and you will develop awareness what you expect for different people. The other thing to look for obviously is asymmetry. Don't forget to assess movement preferences and where they feel it during these maximal tests – useful info.

3) Loaded standing hip abduction 8RM. This is a great test to assess Gmed activation in standing  vs synergists (as with the sidelying straight leg raise). It is the standing hip abductors being tested - pushing down through the heel and pushing the knee outwards helps to increase activation. The key is to get an idea of strength-endurance of the hip abductors under load. Important that the trunk is upright and they hold on to achieve this. A very useful test and often gives you lots of information when the others do not.

If you use all of these tests you can target rehab towards the deficits you find, i.e. activation, function in specific ranges or strength-endurance.

In the interests of keeping this blog brief and easy to digest, I won’t go into hip rotation function testing, although it is important and can give additional information about different segments of the gluteals as well as the deep rotators.

Another consideration is the mechanism driving the deficits you find. Pain is an obvious one, potentially leading to motor cortex changes and inhibition. Also consider atrophy from disuse/long term inhibition. Specific rehab may be warranted e.g. isometrics for pain inhibition.

How do movement patterns fit in?

Excessive pelvic drop in walking is potentially a risk factor for abductor tendinopathy (Allison 2016-see blog 4/2016) and may be related to abductor dysfunction. For example, a shift in length tension of the hip abductors may mean that they are better at producing force at a longer length and this leads to the excessive pelvic movement – Allison Grimaldi (a leading hip clinician-scientist) suggests the force in this instance may come from the superficial muscle system (TFL and upper gluteus maximus), and associated with a poorly functioning Gmed, but it is also possible that the Gmed has a shifted length-tension so prefers to function in a lengthened position – the clue is often in the tests above!

Some people may have excessive pelvic drop in functional tasks but hip abductor tests above seem ok. If you are thorough and do all the tests above you are more confident you have not missed a hip abductor dysfunction, so the explanation may be a neuromuscular or tendon pathology issue that influences activation/rate of force development. Some specific tendon loading, power training or movement pattern retraining may be indicated here.

Other patients will have stiff/protective movement patterns, often associated with irritable pain and pain inhibition. Aside from isometrics, re-establishing movement confidence and variability may be helpful here.

And of course some patients may not have any obvious movement issues, and they may or may not have issues with the hip abductor tests above (biomechanics in not always relevant!). As movement clinicians we still have a job here and that is to develop load tolerance to painful movements, ie again develop movement confidence and variability, ie a progressive exercise and functional restoration approach towards the individual’s goal functions.

Summary

It is critical to be thorough with your hip abductor testing, and keep an open mind about how these findings relate (if at all) to movement. If you do, you can drill down to specific loading interventions for the individual, eg hip abductor activation, inner range loading, strength endurance OR power rehab, movement retraining, etc, etc.

Until next time, keep joining the dots

Peter