American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the consequence of a complete medial collateral ligament tear during valgus stress testing?

1. Pain and swelling

2. Grinding sensation

3. Joint instability

4. Femoral fracture

The correct answer is: Joint instability

A complete tear of the medial collateral ligament (MCL) during valgus stress testing results in joint instability. The MCL is crucial for the stability of the knee, particularly in resisting valgus forces, which push the knee inward. When this ligament is completely torn, the structural support it provides is compromised, leading to significant instability of the knee joint during movements that involve lateral forces. In a clinical setting, this instability becomes evident when the knee is subjected to stress testing, where the inability of the knee to resist the applied valgus force indicates the failure of the MCL to provide the necessary support. Patients may also report feeling as though the knee might give way under stress, and upon examination, increased laxity may be observed compared to the uninjured side. While pain and swelling are common symptoms associated with knee injuries, as well as the presence of a grinding sensation or potential for fractures, the defining consequence of a complete MCL tear during valgus stress testing is primarily the resulting joint instability. This instability is a direct outcome of the ligament's failure and is critical for proper diagnosis and management of knee injuries.