Review Question - QID 3313

This patient has sustained a posterolateral corner (PLC) injury. Posterolateral subluxation of the lateral tibial plateau (Dial test) at 30° but not 90° indicates an isolated PLC injury, while subluxation at both 30° and 90° indicates PLC and PCL injury. The MRI shown in Illustration A is an example of a PLC injury. The iliotibial band (black arrow), lateral collateral ligament (asterisk), and popliteus (white arrow) are all injured. The coronary ligament (black arrowhead) is torn from the tibia, causing displacement of the lateral meniscus (plus sign). The biceps femoris inserts posterior to the LCL as shown in Illustrations B and C. The long head of the biceps femoris muscle has two main parts. A direct arm inserts onto the posterolateral aspect of the fibular head, and an anterior arm crosses lateral to the LCL and inserts on the lateral aspect of the fibular head. The short head of the biceps femoris has a direct tendon insertion onto the superior surface of the fibular head, medial and posterior to the LCL insertion.

The article by Terry and Laprade described a detailed anatomic dissection of the biceps femoris and its many components in 30 cadaveric specimens. The article also included a retrospective review of 82 patients and found that a positive Lachman test correlated to injury to the biceps-capsulo-osseous iliotibial tract confluence. The popliteus inserts at the posteromedial aspect of the tibia, and its tendon originates on the femur at a point distal and anterior to the LCL origination (not proximal to the LCL). The popliteofibular ligament originates at the musculotendinous junction of the popliteus and inserts medial to the LCL insertion on the fibular head (not lateral to the LCL). The anatomy of the posterior oblique ligament and deep medial collateral ligaments are correctly described (option 2 and 5), however they are components of the posteromedial corner (PMC) of the knee and a PMC injury would not exhibit a positive dial test.