JERK

TEST

​• Test positioning

The client lies supine with the involved hip flexed to 45-degrees.

The therapist stands next to the involved side and holds the client's foot.

The therapist's other hand is placed over the lateral aspect of the knee, just behind the head of the fibula.

​• Action

The therapist passively flexes the client's knee to 90-degrees.

Then the therapist extends the client's knee while applying a valgus force and internally rotating the tibia.

​• Positive finding

A shift or "clunk" felt at 30-degrees of knee flexion while the knee is being extended indicates a positive test, implicating anterolateral rotary instability.

If a shift is present, it will reduce upon further passive extension of the knee.

​• Special considerations & comments

This test may not be as sensitive as the pivot shift test.

The Jerk Test is based on the principles developed by Dr. Freddie Fu in assessing ACL injuries and rotational instability of the knee.

Contributions from Dr. James Cyriax have influenced the refinement of this test for orthopedic applications.