Name of test

Quadriceps active test

What it tests

demonstrates PCL deficiency

How to do it

have the patient lie supine with the hip and knee flexed 90 degrees. (you may help by supporting the foot, which is obviously now 1 femur-length off the table; and the patient may find it easier to hold the hip flexed by cradling both hands under the thigh.)

ask the patient to actively extend the leg.

observe.

The normal response

the knee appears to 'hinge' as the leg extends

What it means if not normal

if the pcl were deficient, the knee is NOT in a normal position at the start of the test: the tibia will be subluxated posteriorly (sagging) as there is no pcl to hold it in place. thus, when the quad fires to extend the knee, it's first action is to pull the tibia back to its normal place-given that the quad attaches to the anterior tibia via the patellar tendon-and only thereafter extend the knee joint.

Comments

this test is striking only with significant posterior displacement. also, in the acutely injured (and swollen) knee, a positive test may not be obvious

Citations