The dial test is performed to help detect an injury to the posterolateral corner (PLC) of the knee. External rotation of the tibia is compared while the knees are flexed to 30 degrees and to 90 degrees, with a difference of more than 10 to 15 degrees constituting a positive test. A positive test at 30 degrees of flexion but negative test at 90 degrees suggests an isolated PLC injury, whereas a positive dial test at both 30 and 90 degrees of flexion suggests injury to both the posterior cruciate ligament (PCL) and PLC.
