American Board of Internal Medicine (ABIM) Certification Practice Exam

What symptom is common in a complete lateral collateral ligament tear?

1. Medial joint instability

2. Lateral knee pain and swelling

3. Femoral nerve damage

4. Popliteal cyst formation

The correct answer is: Lateral knee pain and swelling

In the case of a complete lateral collateral ligament (LCL) tear, lateral knee pain and swelling are common symptoms. The LCL is responsible for providing stability to the outer aspect of the knee, hence a tear can lead to significant pain localized to that area. The mechanism of injury often involves a force that causes excessive stress on the lateral side of the knee, which typically results in a cascade of inflammatory responses. This inflammation manifests as swelling around the knee joint. Patients often report tenderness along the LCL, and this pain is usually exacerbated by activities that stress the lateral aspect of the knee, such as pivoting or lateral movements. Other symptoms associated with LCL tears may include instability of the knee, but it primarily presents with pain along the lateral joint line and surrounding swelling. Understanding the injury mechanism and resultant symptoms helps clarify the clinical presentation of an LCL tear, emphasizing why lateral knee pain and swelling is a hallmark symptom following such an injury.