American Board of Internal Medicine (ABIM) Certification Practice Exam

What is a typical finding in a physical exam for medial collateral ligament tears?

1. Pain with passive flexion

2. Swelling above the knee

3. Increased laxity with varus stress testing

4. Increased laxity with valgus stress testing

The correct answer is: Increased laxity with valgus stress testing

In the context of a medial collateral ligament (MCL) tear, increased laxity with valgus stress testing is indeed a typical finding. The MCL is responsible for stabilizing the knee against forces that push the knee inward (valgus forces). When the ligament is injured or torn, it loses its ability to adequately support the joint, leading to increased laxity when the knee is subjected to a valgus stress test. During the examination, the examiner applies a force to the outer side of the knee while stabilizing the ankle. In a healthy knee, this maneuver should result in minimal movement. However, if the MCL is compromised, the knee will exhibit increased movement or laxity. This physical response is a clear indicator of the integrity of the MCL. The other findings related to knee injuries typically do not specifically correlate with MCL tears in the same manner. Pain with passive flexion, swelling above the knee, and increased laxity with varus stress testing refer to other possible ligamentous injuries or knee conditions not specifically associated with MCL integrity. Understanding the role of the MCL and the implications of the valgus stress test is essential for correctly diagnosing an MCL tear.