A football player was simultaneously tackled from the front above the knee and from the back below the knee. In the emergency room, he displays a positive anterior drawer test which becomes negative if the knee is internally or externally rotated. Which of the following has ruptured?
A. anterior cruciate ligament
B. fibula
C. fibular (lateral) collateral ligament
D. posterior cruciate ligament
E. tibial (medial) collateral ligament
Ans:A. anterior cruciate ligament