Which movement tests the integrity of the lateral collateral ligament (LCL) of the knee?

• A. Extension test.
• B. Varus stress test.
• C. Flexion test.
• D. Valgus stress test.

Answer: (B)

The integrity of the lateral collateral ligament (LCL) of the knee is best assessed through the varus stress test. This test specifically targets the LCL, which is located on the outer side of the knee. During the varus stress test, the examiner applies a controlled force to the knee while stabilizing the ankle, creating a varus force that stresses the lateral side of the joint. If the LCL is intact, the knee will maintain its normal alignment and there won’t be significant lateral movement. However, if the LCL is injured, there will be increased movement or pain on the lateral aspect during the test, indicating a potential tear or dysfunction of the ligament.

Other options do not specifically test the LCL. The extension test primarily examines the knee's ability to straighten, while the flexion test looks at the knee's ability to bend, both of which do not specifically isolate the lateral collateral ligament. The valgus stress test, conversely, assesses the medial collateral ligament (MCL) by applying a force to stress the inner side of the knee, making it unrelated to the evaluation of the LCL.