3 Tips To A Better Knee Assessment
Posted By: Andy Barker
The knee should be a pretty straight forward joint to test.
The joint itself is relatively simple…
It’s a modified hinge joint, it flexes and extends (it also internally and externally rotates when flexed)…
And has a muscles to front (quads) and back (hamstrings and calfs) that give it active support.
But I am sure as simple as knee might appear, you have had some patients with knee pain that you have found tricky to deal with.
You may have struggled with your objective assessment and be unsure what the diagnosis is.
Maybe you feel you do too many special tests, even when they you can not really reason why you are doing them (this is really common) or…
Maybe you worry that you might miss an important injury at the knee, like an ACL injury.
To help you out here are 3 tips to help you better make sense of the knee and help you conduct a better knee objective assessment.
#1 Know Your Tests
Special tests of the knee generally have good sensitivity and specificity.
This means that it should be easier for you to identify exactly what structure is causing your patients pain, compared with other joints like the shoulder..
However, this all depends on you being able to perform the tests well on your patient.
The best test done badly, will probably give you the wrong result.
This might be a false positive or false negative result, but either way, it will probably lead you to the wrong diagnosis.
Also, you need to make sure you do the right test.
For every possible injury at the knee, you should have a test in mind that you could use on your patient to rule in, or out, this potential diagnosis.
ACL = Lachman’s
MCL = Valus test
LCL = Varus
Meniscus = McMurray’s
You get the idea.
When presented with knee pain (or any injury for that matter) you should NOT just test everything.
This is one of the many errors I see therapists doing all the time, especially new grads.
Assessing a knee and just testing every possible injury, even when the subjective assessment does not warrant this.
This was the approach you were taught at University, but there is a big problem with this (see #2).
The aim with any testing is to be as specific as possible and special testing is no different.
Fail to do this and you risk gaining a false positive or false negative result or even worse…
You might miss an important injury like an ACL.
#2 Do Your Tests In The Right Order
Two things should influence the ordering of your special testing.
Firstly, you should pick the most relevant test, or tests, for the suspected injury you think your patient has, having completed your subjective assessment.
This is your primary hypothesis.
For example, if you suspect an ACL injury, you might conduct a Lachman’s or anterior draw test.
Hopefully you are already doing this.
Secondly, if you suspect or want to rule out other injuries, you should always try to test the least provocative tests first.
With the ACL example above, you may want to clear an MCL or medial meniscal injury, two commonly seen injuries with an ACL mechanism of injury.
Having tested the ACL first, you might then do a valgus stress test (MCL) followed by a McMurray’s test (meniscus).
The MCL valgus test is an isolated test, which tests the integrity of the MCL.
The McMurray’s test, whilst a meniscal test, the motion of the test will provide a valgus force to the knee, and as such will stress the MCL too.
So by doing the McMurray’s test before the MCL valgus test you might have already tested the MCL, and as such provoked it.
This provocation might be pain and/or apprehension.
So, by the time you come to test the MCL, the medial knee is already painful or the patient might start to guard during testing because the knee is sore.
So the pain you get on MCL testing is hard to interpret.
Is the knee still sore from the previous test (McMurray’s) or do they actually have an MCL injury?
There is no way to determine this and as such the test is almost a waste of time.
If the patient is apprehensive and will not relax to let you test the knee then you cannot test it properly…
So you might also miss something important.
Whatever your primary hypothesis of injury is…
…test this first.
If you think you may have to test multiple structures in the knee, think about what order you are going to test as this will have a big impact on your testing results.
#3 Find What Tests Work For You
Whilst you should always aim to use the best tests and those that have the best sensitivity and specificity, unfortunately it is not as easy as that.
The most important thing is that you select the right test and perform the test properly.
If you look at the evidence most would point to the Lachman’s test as the ‘best’ test to use to rule in or out an ACL injury (based on sensitivity and specificity scores).
However, it is not my primary choice when trying to rule in or out an ACL injury.
I always found the Lachman’s test hard to perform correctly when I first started out.
I was working in professional rugby and I found that trying to grip my hands around their proximal calf with one hand, to get in position to do a Lachman’s test, pretty tough.
Players generally are pretty muscular and have big calves, and whilst I don’t have small hands by any means, I found using another ACL test, the anterior draw test, much easier.
So I generally used that that test instead, as my primary ACL instability test.
I ultimately felt that I got a better ‘test’ using the Anterior Draw Test versus the Lachman’s test and for that reason it is my ACL test of choice.
You should always be guided by the evidence…
But just as important as the evidence is real life.
You need to be able to complete whatever special test you select well…
Otherwise the test is going to be far from ‘special’ and will most likely give you the wrong result!
- Know Your Tests – You can’t ‘test’ a structure if you don’t know what test you need to use to stress that structure. Ensure you know a special test for every knee injury you might be faced with.
- Do Your Tests In The Right Order – Pick your primary hypothesis and test that structure first. After that, choose the tests that are the least provocative, so you reduce the chances of you irritating your patients knee and risk picking up an incorrect test result.
- Find A Test That Works For You – You should always be guided by the evidence but just as important is your ability to do the test properly. Kind out what tests work well for you to ensure you find the right diagnosis.
Hope this helps!
The New Grad Physio Mentor
PS. Want to know more about how to better assess the knee and learn how to select the right special tests?
Want to feel more confident when giving your patients the right treatment techniques and rehab exercises, and stop having tor change your exercises every session because they are mot working?
Want to learn more about how to manage patients with injuries like patella tendinopathy, patella-femoral joint pain, ACL, PCL or MCL injuries?
I have a whole module in my new grad physio membership just on the knee.
Find out how to get access to this and loads more content right here.