Thessaly Test

For Medical Students

What It Tests

The Thessaly test asks the patient to rotate the body on a flexed, weight bearing knee, which compresses and rotates the meniscus under load.

That load is what distinguishes it from the other tests in this chapter, all of which are performed on a couch with the knee unloaded.

It tests the meniscal body and posterior horn under conditions closer to those that produce the patient's symptoms.

How It Is Performed

Ask the patient to stand and support themselves by holding your hands or a stable surface.

Have them stand on the affected leg with the knee flexed, conventionally at about twenty degrees, and then rotate the body and the knee internally and externally three times.

Watch for discomfort, a sense of locking or catching, and ask whether the manoeuvre reproduces their pain.

Test the unaffected side first so the patient knows what is being asked and you have a comparison.

Do not perform it in a knee that cannot bear weight or that is acutely locked.

What a Positive Means

Joint line discomfort, or a sense of catching or locking during the rotation, with recognition of their pain, is a positive.

A positive on the affected side with a normal unaffected side is more informative than a positive alone.

Pain at the front of the knee rather than the joint line during the manoeuvre is patellofemoral rather than meniscal, because the position loads the patellofemoral joint too. 4.15.9 covers it.

An inability to perform the test is a finding in itself and usually reflects pain or instability rather than a specific structure.

MRCS Level

How It Is Performed

In a viva the expected points are the weight bearing position, the flexion angle, the rotation in both directions, the comparison side and the supervision.

The candidate should say why it is done weight bearing, which is the whole rationale: compression plus rotation reproduces the loading that provokes meniscal symptoms.

Say that the test is performed at a stated flexion angle, because the angle changes which part of the meniscus is loaded, and that the angle should be recorded. 4.1.8 covers the record.

Say that you would not perform it in an acutely injured or locked knee.

What a Positive Means

The test's positive is a reproduction of the patient's symptom under load, which is a different claim from reproducing pain on a forced passive manoeuvre.

That makes a positive more clinically meaningful, because the loading resembles the activity that troubles them.

It also makes a positive harder to attribute, because weight bearing flexion with rotation loads the patellofemoral joint, the cartilage and the collaterals at the same time.

So the site of the reported discomfort matters more in this test than in the others, and joint line localisation is what makes it meniscal.

How Good It Is

The Thessaly test was introduced as a more accurate alternative to the older provocative tests, and the subsequent literature has been less favourable than the original reports.

The honest position is that it performs comparably to the other provocative tests rather than clearly better, and that early enthusiasm was based on reports that have not been consistently reproduced.

It shares the group's pattern: more specific than sensitive.

Its advantage is physiological rather than statistical, in that it loads the knee the way the patient does.

No figures appear, under decision 023, and the claim being made is the comparison rather than a number. 3.17.3 covers how the meniscal literature behaves generally.

FRCS Level

How Good It Is

At decision level the Thessaly test is useful for a purpose the other tests do not serve: it demonstrates the symptom to the patient and to you under the loading they complain about.

That makes it valuable in the consultation where the question is whether the imaging finding is the problem, which is the central question of this chapter. 4.9.11 covers the degenerate version.

It also gives a functional baseline that can be repeated, which few of the tests in this chapter do.

It does not settle repairability, compartment or urgency, and treating it as a more accurate McMurray overstates what the literature supports.

Where It Misleads

The commonest error is treating it as more accurate than the older tests on the strength of the original reports.

The second is attributing a positive to the meniscus when the position loads several structures, which is why the site of discomfort has to be asked rather than assumed.

The third is performing it in a patient who cannot safely stand on one leg, which turns an examination into a fall risk.

And recording it without the flexion angle, which makes it non-comparable at the next visit.

Fellowship Level

Where It Misleads

After meniscal surgery the weight bearing rotation test retains more value than the passive tests, because it tests function rather than attempting to trap a fragment.

A patient who can rotate under load without symptoms after a resection has a functionally satisfactory knee whatever the imaging shows.

A patient who cannot has a problem, and the test does not say whether it is a new tear, altered mechanics or cartilage. 4.9.10 covers deficiency.

After a repair the test loads the repair and should not be used during the protected period. 4.20.2 covers repair assessment.

At this level the test is better thought of as a functional measure than a diagnostic one, which is how 4.21 treats the hop and squat tests. 4.21.1 covers the single leg squat.

No figure here supports these claims, under decision 023.