Name of test

Valgus stress test of the knee

What it tests

assesses the medial collateral ligament and medial capsule

How to do it

this test is done twice: once in full extension and once in 30 degrees of flexion

(for purposes of description, we'll assume that it's the right knee being examined)

the patient lies supine with the leg extended on the table

the examiner places her left hand on the outer (lateral) of the knee, palm against the joint line. with the right hand, she grasps the medial ankle and lifts the leg off the table. using the left palm to stabilize the leg, she then applies a VALGUS force to the knee, by pushing laterally on the ankle. if the test is normal, it is repeated with the knee slightly bent.

The normal response

the knee should remain stable, that is, not gap open, and no pain should be reported.

What it means if not normal

there are three variations:

gapping of the knee with no good end point (and usually little pain) = MCL rupture, grade III sprain

some gapping of the knee with an end point (and usually lots of e pain) = MCL grade II sprain

no gapping, but pain = grade I sprain.

NB: if the knee is stable in full extension but unstable in slight flexion, that reflects an isolated MCL injury. If there is instability in full extension, there is damage to the knee capsule (and possibly the cruciates as well)

Comments

note that there may be so-called 'pseudo-laxity' in which there is a varus deformity to begin with (bow-legged) which then "corrects" to normal with valgus stress. This reflects medial joint space narrowing, often from arthrosis.

Citations