American Board of Internal Medicine (ABIM) Certification Practice Exam

Which examination finding is associated with an anterior cruciate ligament tear?

1. Medial joint line tenderness

2. Increased laxity with valgus stress testing

3. Large effusion with laxity in drawer tests

4. Pain with internal rotation of the knee

The correct answer is: Large effusion with laxity in drawer tests

The examination finding most closely associated with an anterior cruciate ligament (ACL) tear is a large effusion accompanied by laxity in drawer tests. When an ACL tear occurs, it often leads to instability of the knee joint, which can manifest as significant swelling (effusion) due to bleeding and inflammation within the joint. This effusion can be quite pronounced shortly after the injury. Furthermore, the anterior drawer test is specifically designed to assess the integrity of the ACL. In an individual with an ACL tear, the test reveals increased forward translation of the tibia relative to the femur, indicating laxity. The presence of both a large effusion and laxity on testing supports the diagnosis of an ACL injury effectively, as they are classic signs resulting from the ligament's disruption. Other options like medial joint line tenderness and pain with internal rotation may relate to other knee injuries, such as meniscus tears or other ligamentous injuries, but do not directly pertain to ACL functionality as indicated by the combination of effusion and drawer test laxity. Increased laxity with valgus stress testing is more characteristic of injury to the medial collateral ligament (MCL) rather than the ACL. Therefore, the combination of large effusion and laxity observed in drawer