Dial Test (or tibial external rotation test) is used in evaluation of posterolateral instability of the knee. It is used to assess abnormal external tibial rotation to help differentiate between an isolated posterolateral corner injury and combined Posterior Cruciate Ligament (PCL) / posterolateral corner (PLC) injuries.
How it’s Performed?
The patient lies in the supine position with the knee flexed to 30 degrees over the edge of the table.
The clinician applies an external rotation force to the patient foot by placing the fingers and thumb alongside the talocalcaneal bone contours.
The foot–thigh angle is measured and compared with the uninjured knee.
The test is then performed with 90 degrees of knee flexion and the foot–thigh angle is remeasured.
This test can be done with prone position.
What does a positive Dial Test mean?
When comparing the two angles, a difference of 10 degrees or more is significant and the Dial test is positive.
As the knee is flexed to 90 degrees, a reduction in increased rotation may occur although the amount of motion remains greater than the uninjured side if the Posterior Cruciate Ligament (PCL) is still intact. This increased rotation occurs because the Posterior Cruciate Ligament (PCL) is a secondary stabilizer to external rotation and gains mechanical advantage when the knee is flexed.
In this case, there are three types of injuries:
An isolated injury of the posterolateral corner (PLC): there are more than 10° of external rotation in the injured knee only at 30° of flexion, but not at 90° of flexion.
Posterior Cruciate Ligament (PCL) Instability: there are more than 10° of external rotation in the injured knee at 90° of flexion, but not at 30° of flexion.
A combined injury (PCL & PLC): there are more than 10° of external rotation in the injured knee at 30° and 90° of flexion.
Posterolateral Corner (PLC):
The Posterolateral corner (PLC) consists of superficial and deep layers:
The superficial layer is comprised of the:
The biceps femoris tendon.
The iliotibial band.
The deep layer is comprised of:
The lateral collateral ligament (LCL).
The popliteus tendon.
The arcuate ligament.
The popliteofibular ligament.
The fabellofibular ligament.
Injuries of the posterolateral corner of the knee (posterior cruciate ligament, lateral collateral ligament, posterior joint capsule, and the popliteus tendon) result in a varus thrust gait pattern during stance.
Posterior Cruciate Ligament (PCL):
The average length of the PCL is 38 mm; the average width is 13 mm.
The femoral attachment is a broad, crescentshaped area anterolateral on the medial femoral condyle (30 mm long and 5 mm wide).
The tibial attachment is in a central sulcus on the posterior aspect of the tibia, 10 to 15 mm below the articular surface.
The meniscofemoral ligaments (ligaments of Humphrey and Wrisberg) are present 70% of the time; they originate from the posterior horn of the lateral meniscus and insert into the substance of the PCL and the medial femoral condyle.
The ligament of Humphrey is anterior to the PCL.
The ligament of Wrisberg is posterior to the PCL.
The innervation and vascularity of the PCL are similar to the ACL but with a more generous blood supply.
Clinical Tests for the Musculoskeletal System 3rd Edition.
Dutton’s Orthopaedic Examination, Evaluation, And Intervention 3rd Edition.