Final answer:
The positive anterior/posterior drawer sign after Daniel's football injury indicates a likely injury to the Anterior cruciate ligament (ACL), which is responsible for resisting hyperextension of the knee and commonly injured by forceful blows or sudden changes in direction.
Step-by-step explanation:
When Daniel, age 18, exhibits a positive anterior/posterior drawer sign after a football injury to his right knee, this test indicates an injury to the: 1) Anterior cruciate ligament (ACL). The anterior drawer test assesses the stability of the ACL by checking for excessive anterior displacement of the tibia in relation to the femur.
The ACL is an intracapsular ligament of the knee that extends from the anterior, superior surface of the tibia to the inner aspect of the lateral condyle of the femur, and it resists hyperextension of the knee. Common causes of ACL injury include a forceful blow to the anterior knee, producing hyperextension, or when a runner makes a quick change of direction that produces both twisting and hyperextension of the knee.
In contrast, injury to the medial collateral ligament (MCL) usually occurs due to a strong blow to the lateral side of the extended knee, causing the medial side of the joint to open. The posterior cruciate ligament (PCL) is typically injured when the knee is flexed and the tibia is driven posteriorly. Lastly, the lateral collateral ligament (LCL) is injured less frequently and usually due to a direct force to the medial side of the knee.