Review Question - QID 5452

This patient has sustained an anterior cruciate ligament (ACL) rupture.

The ACL is the primary restraint to anterior translation of the tibia relative to the femur. It also acts as secondary restraint to tibial rotation and varus/valgus rotation. ACL-deficient knees have been shown to have abnormal knee kinematics, which has been thought to contribute to the osteoarthritis that develops after injury.

DeFrate et al. examined the knee joint kinematics of 8 patients with unilateral anterior cruciate ligament rupture using in vivo imaging. They found significant anterior shift and internal rotation of the tibia at low flexion angles in ACL-deficient knees. They also noted some medial translation of the tibia between 15° and 90° of flexion.

Illustration A shows the effect of medial tibial translation on tibiofemoral contact in ACL-deficient knees. The medial translation of the tibia causes increased contact between the tibial spine and inner surface of the medial femoral condyle. This might be a contributing factor to the joint degeneration observed in ACL-deficient patients.

Incorrect Answers:
Answer 2: Posterior cruciate ligament deficiency would cause a posterior shift of the tibia
Answer 3: Posterior cruciate ligament and medial collateral ligament deficiency would theoretically cause increased internal rotation and posterior translation of the tibia
Answer 4: Medial collateral ligament deficency would cause increased valgus rotation and slightly increased internal rotation.
Answer 5: Lateral collateral ligament, popliteal tendon and arcuate ligament injuries collectively make up a posteriolateral corner injury. This would cause increased external rotation of the tibia.