A 20-year-old man comes to the hospital with knee pain after he tripped and landed on his right knee during a soccer game. The anterior portion of his tibia impacted directly against the ground, and he has been unable to bear weight since the injury. On physical examination, the patient's knee appears swollen, and there is excessive posterior displacement of the tibia when pressure is applied to his anterior tibia with the knee in the flexed position. An axial MRI cross section of the right knee at the level of the tibial plateau is shown below. Which of the following structures is most likely injured in this patient?

Question

A 20-year-old man comes to the hospital with knee pain after he tripped and landed on his right knee during a soccer game.  The anterior portion of his tibia impacted directly against the ground, and he has been unable to bear weight since the injury.  On physical examination, the patient's knee appears swollen, and there is excessive posterior displacement of the tibia when pressure is applied to his anterior tibia with the knee in the flexed position.  An axial MRI cross section of the right knee at the level of the tibial plateau is shown below.  Which of the following structures is most likely injured in this patient?

Quizplus · Accepted Answer

11ec160b_35e6_ebf3_9249_bb2f482dbf68_MD0001_00 The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) are found within the articular capsule of the knee joint and cross one another as they span from the femur to the tibia. The PCL originates from the anterolateral surface of the medial femoral condyle and inserts into the posterior intercondylar area of the tibia. At the level of the tibial plateau (as seen on the axial MRI above), the ACL is anterior, and the PCL is posterior. The ACL functions to resist anterior displacement of the tibia relative to the femur (Choice A). The PCL prevents posterior displacement of the tibia relative to the femur, and its integrity can be tested by using the posterior drawer test (posterior force applied to the tibia while the knee is flexed). PCL tears most commonly occur following a direct blow to the anterior proximal tibia during sporting activities or motor vehicle collisions. (Choices B and E) The medial and lateral menisci are crescent-shaped bands of cartilaginous tissue that line the periphery of the knee joint. Meniscal tears are associated with twisting of a flexed knee while the corresponding foot is planted. Meniscal damage can be detected on physical examination by joint-line tenderness during provocative maneuvers (eg, McMurray test). (Choice C) The patellar ligament (ie, patellar tendon) connects the inferior portion of the patella to the tibial tuberosity. Patellar ligament rupture is associated with underlying ligamentous damage (eg, autoimmune disease, overuse injury) and usually occurs following forceful contraction of the quadriceps muscles while the knee is flexed (eg, landing after a jump). A complete patellar ligament tear would result in swelling and a high-riding patella on physical examination. Educational objective: The posterior cruciate ligament prevents posterior displacement of the tibia relative to the femur. It originates from the anterolateral surface of the medial femoral condyle and inserts into the posterior intercondylar area of the tibia. Its integrity can be tested in the clinical setting by using the posterior drawer test.

A 20-Year-Old Man Comes to the Hospital with Knee Pain