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.
See Also: Knee Ligaments Anatomy
How do you Perform the Dial Test?
- The patient lies in the prone position with the knee flexed to 30 degrees.
- Using the medial border of the foot as a point of reference, the examiner forcefully externally rotates the patient’s lower leg.
- The position of external rotation of the foot relative to the femur is assessed and compared with the opposite extremity.
- The knee is then flexed to 90° and the test repeated.
- Care must be taken to keep the hips from abducting during the examination.
- A goniometer can be used to quantify the amount of external rotation.
Normal variations for rotation are expected. The dial test results of one extremity must be compared with those of the opposite leg.
If performed with the patient in the supine position, the tibia should be anteriorly translated to its original position by a second examiner.
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.
See Also: PCL Injury
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 capsule.
- 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.
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