

The Prone Instability Test is an orthopedic test to assess radiographic lumbar Instability – one possible cause of chronic low back pain.
Several authors have evaluated this test regardings its inter-rater reliability and have found Kappa values between 0.46 (weak) and 0.87 (strong).
However, when it was examined regardings its accuracy to diagnose radiographic lumbar instability it showed weak sensitivity and specificity values, which
makes this test a poor diagnostic test in clinical practice.
The test consists of two parts. During the first part, you ask the patient to lie prone with his legs hanging off the bench, but with contact with the ground. Then you are applying PA pressure to different segments of the lumbar spine, and you are trying to provoke pain.
If pain is provoked, you ask the patient to lift his legs off the ground, and you apply PA pressure again. If the patient’s pain is reduced by actively bringing the legs off the ground, this means that the patient is able to actively stabilize his spine, which is a positive test.
A positive test also implies that a stability exercise program would be suitable for such a patient.
There are several other orthopedic tests for the diagnosis of radiographic lumbar instability: