A 16-year-old boy comes to the emergency department due to right knee pain after a fall. His symptoms started after a ski accident in which he twisted the right lower leg outward relative to the thigh. He has no medical conditions and currently takes no medications. On examination, there is swelling and tenderness on the medial aspect of the right knee. Widening of the medial joint line can be felt when a gentle force is applied to the lateral knee with the lower leg kept stationary. Which of the following labelled structures is most likely injured in this patient?

Question

A 16-year-old boy comes to the emergency department due to right knee pain after a fall.  His symptoms started after a ski accident in which he twisted the right lower leg outward relative to the thigh.  He has no medical conditions and currently takes no medications.  On examination, there is swelling and tenderness on the medial aspect of the right knee.  Widening of the medial joint line can be felt when a gentle force is applied to the lateral knee with the lower leg kept stationary.  Which of the following labelled structures is most likely injured in this patient?

Quizplus · Accepted Answer

11ec160b_35e9_840e_9249_55f48c999e09_MD0001_00 This patient has an injury to the medial collateral ligament (MCL). The MCL attaches proximally to the medial epicondyle of the femur and resists forces that push the knee medially. MCL injury typically occurs after a twisting injury or blow to the lateral knee while the foot is planted (valgus stress injury). The valgus stress test is performed with the knee extended by placing one hand along the lateral thigh and pressing inward while the other hand is placed on the medial aspect of the ankle and pushed outward. Laxity of the knee and/or medial joint line widening indicates MCL injury. (Choices A and E) The lateral (A) and medial (E) menisci reduce shock and help transfer force from the upper to the lower leg. Medial meniscal injury can occur with twisting movement of the knee and often accompanies MCL injury. Lateral meniscal injury is less common. Meniscal injury is diagnosed by joint line tenderness while the knee is flexed. (Choice B) The lateral collateral ligament (LCL) resists excessive lateral movement of the knee. LCL injury is uncommon but would be characterized by laxity of the knee with varus stress. (Choice C) The anterior cruciate ligament (ACL) resists anterior movement and medial rotation of the tibia. Injury is indicated by increased anterior movement of the tibia in relation to the femur (eg, anterior drawer test, Lachman test). (Choice D) The posterior cruciate ligament (PCL) stabilizes the tibia and femur during knee movement. Excessive backward movement of the tibia in relation to the femur (posterior drawer test) indicates PCL injury. Educational objective: The medial collateral ligament resists force that pushes the knee medially. Increased laxity of the knee with the valgus stress test indicates injury to the medial collateral ligament. __________ References: MCL injuries of the knee: current concepts review. (http://www.ncbi.nlm.nih.gov/pubmed/16789454)

A 16-Year-Old Boy Comes to the Emergency Department Due to Right