American Board of Internal Medicine (ABIM) Certification Practice Exam

What indicates a complete tear of the medial or lateral collateral ligament?

1. Knee instability and a popping sound

2. Swelling and joint line tenderness

3. Positive Thessaly test

4. Patellar taping effectiveness

The correct answer is: Knee instability and a popping sound

A complete tear of the medial or lateral collateral ligament is typically indicated by knee instability, which manifests as a feeling of looseness or instability in the knee during movement, coupled with a popping sound at the time of the injury. This popping often signifies an acute injury where the ligament has been fully compromised, leading to a significant loss of structural support. While swelling and joint line tenderness can be present in various knee injuries, including partial tears, these symptoms alone do not specifically pinpoint a complete tear of the collateral ligaments. The same is true for the positive Thessaly test, which is primarily used to assess meniscal tears rather than collateral ligament integrity. As for patellar taping effectiveness, it relates to how well the patellar alignment is supported and does not pertain directly to determining the status of the collateral ligaments. Thus, the indication of knee instability combined with a popping sound is key in confirming a complete tear of the collateral ligament.