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The Thomas Test

The Thomas test is one of the most common tests you will see on your COMLEX, COMAT, and the USMLE.

For this reason, in this article, we will cover all the important details about the Thomas test so that you can absolutely rock these questions on your exams, and accurately perform the Thomas Test on your rotations in 3rd year.

Knowing the specifics of this test and the many others tests like it are what helped me succeed at a high level in medical school.

You see, I barely got into medical school, I had a very average MCAT score and a less than impressive GPA in undergrad.

Ultimately, I ended up graduating medical school with a 4.0 GPA and scoring in the 97th percentile on both my COMLEX Level 1 and Level 2 CE.

It was during my 4th year that I decided to start COMPREPMED to help other medical students find the success I had throughout my medical school experience and to help them get their #1 choice residency like I did.

So, back to the reason you are here, the Thomas Test.

This article will cover:

Lets get into it!

What is the Thomas Test?

The Thomas test is a special physical exam test that is commonly used to evaluate the iliopsoas muscle.

To perform this test the patient will:

  • lay on their back
  • their legs lay off of the exam table at about the knee
  • then they will pull one knee into their chest at a time

If the patient pulls their right knee into their chest, you are testing the left iliopsoas. If the patient pulls their left knee into their chest, you are testing the right iliopsoas.

Here is a video to demonstrate the Thomas test and what you are looking for in the test.



What does a positive Thomas test mean/Look like?

A positive Thomas test simply means a hypertonic (tight) iliopsoas.

If the patient pulls their right knee into their chest, you are testing for a hypertonic left iliopsoas and vice versa.

So, what does a positive test look like?

In this image you can see the patient pulling her knee into her chest and the opposite leg that is still laying on exam table has elevated off the table and has created some extra space between her leg and the table.

This extra space or the “lifting” of the leg off the table is what a positive Thomas test looks like.

What does a negative Thomas test mean/look like?

A negative Thomas test is just the opposite of a positive one… well duh right?

If the patient pulls their knee into their chest, the opposite leg if it is a negative Thomas test will not lift off of the table, it will just lay flat and not move much.

This image shows what a negative Thomas test looks like.

Thomas Test Patient Scenarios

Alright, so now that we have gone through the mechanics and meaning of the Thomas test, we need to dive into how you will see the Thomas test comes up in questions.

The most common scenario that you will see a Thomas test presented to you will be on a “low back pain” patient question on exams.

The scenario will be as follows:

  • The patient will be complaining of low back pain, they will have just been sitting in a car or sitting down for whatever reason for a very long time, or possibly they began exercising and their new exercise involved jumping.

These are the three key points: If you see a question mention that the patient has #1 back pain, #2 been sitting for a long time or doing an exercise such as box jumping, #3 has an increased lordotic curve in their L spine, then you can bet they are trying to point you towards assuming the iliopsoas is hypertonic.

That same question will then go on to talk about the “test” that you should use to evaluate the patient, or possibly they will ask you to interpret a test from words or a short video. Lets go over what you could expect to find in the question asking you to “interpret these test results” from a short description.

The description of the “test” may be as follows: The patient lays supine, pulls their right knee into their chest and as they do this their left leg lifts off of the table creating space between their popliteal fossa and the exam table.

This is how they would possibly present the “description” of the exam to you.

They might also simply show you a video like I showed you above demonstrating the Thomas test itself.

After this the answer choices will likely ask you to state which psoas is tight, what test they are using, or where the muscle being tested originates or attaches, so lets cover these things as well.

If they pull the right knee into their chest and the left leg lifts off the table then the left iliopsoas is tight.

If they pull the left knee into their chest and the right leg lifts off the table then the right iliopsoas is tight.

They are obviously using the Thomas test.

The psoas muscle originates in the T12-L5 vertebral area and it inserts onto the lesser trochanter of the femur.

These are important things to know, because for some reason the Thomas test and its meaning is so important to test writers, be it block exams or exams you will take.

Also, if you found this information helpful then be sure to check out CPM OMM.

CPM OMM is an OMM review course that covers the Thomas test and many other tests like it in the great detail that I have done in this article.

The course is largely geared towards helping you get more points on any given test day, while minimzing the time you actually have to study OMM. In other words, the content in the course is taught in an extremely efficient, high yield and organized manner.

Check out CPM OMM here.

Thanks for reading,

Sean Kiesel D.O.

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