What is the purpose of the valgus stress test?

• A. To assess lateral collateral ligament integrity
• B. To assess medial collateral ligament integrity
• C. To assess posterior knee stability
• D. To assess meniscal integrity

Answer: (B)

The key idea is that this test evaluates the medial collateral ligament by applying a valgus (inward) force to the knee. When you push the knee inward, you stress the inner (medial) side where the MCL resides. If the MCL is injured, the medial joint space opens more than normal and there may be pain or gapping compared to the other knee. Performing the test with the knee flexed around 20–30 degrees helps isolate the MCL from other structures, giving a clearer indication of MCL integrity. If the test shows no excess medial gapping, the MCL is likely intact.

This test specifically targets the MCL; testing for LCL injury uses a varus (outward) stress, not a valgus one. It isn’t a test for posterior knee stability or meniscal integrity, which are evaluated with different maneuvers (e.g., posterior stress tests or McMurray/Apley), respectively.