This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
A person after a road traffic accident had a knee injury. A positive 'dial test' in the patient would indicate injury to the following structure: 
Select and explain. 
A. Medial collateral ligament, B. Lateral meniscus, C. Medial meniscus, D. Posterolateral corner
D: Posterolateral corner
Answer: D: Posterolateral corner 
Explanation: External Rotation Recurvatum Test or 'Dial test': This test is performed with the patient supine and the hip and knee fully extended. The leg is lifted off the bed by the toes. Hyperextension, varus instability, and external rotation of the tibial tubercle occurs with adequate quadriceps relaxation in a patient with posterolateral instability. Ref: McMahon P.J., Kaplan L.D. (2006). Chapter 4. Spos Medicine. In H.B. Skinner (Ed), CURRENT Diagnosis & Treatment in Ohopedics, 4e.