A 22-year-old male basketball player presents with a swollen, painful left knee. He was on a fast break and as he began to jump for an alley-oop, he felt his knee give out and he collapsed to the floor. What is the most likely diagnosis: (A) Patello-femoral dislocation, (B) Anterior cruciate ligament injury, (C) Medial collateral ligament injury, (D) Posterior cruciate ligament injury
Answer is B. The history provided describes a noncontact injury to the knee during an acceleration-deceleration/pivoting move with the patient experiencing a feeling of giving way in his knee. The player quickly accumulates a knee effusion and has significant pain. These findings are characteristic descriptions of an ACL injury. The Lachman test is diagnostic for this injury, and an MRI would confirm the diagnosis.