American Board of Internal Medicine (ABIM) Certification Practice Exam

What condition is indicated by anterior knee pain and swelling with a palpable fluid collection?

1. Osteoarthritis

2. Prepatellar bursitis

3. Patellar tendinitis

4. Runner's knee

The correct answer is: Prepatellar bursitis

The condition indicated by anterior knee pain and swelling with a palpable fluid collection is prepatellar bursitis. This condition occurs when the bursa located in front of the kneecap (patella) becomes inflamed, often due to repetitive movements or direct trauma to the area. The swelling results from excess fluid accumulation in the bursa, leading to a noticeable fluid collection that can be palpated, often described as a "water on the knee." Patients with prepatellar bursitis typically experience pain at the front of the knee, especially when kneeling or applying pressure to the knee, which is common in individuals whose activities involve frequent bending of the knee or kneeling, such as carpenters or plumbers. In contrast, osteoarthritis generally leads to joint pain and stiffness due to cartilage degeneration but does not usually present with a palpable fluid collection. Patellar tendinitis, often referred to as "jumper's knee," involves pain at the patellar tendon insertion but does not typically cause significant swelling or fluid collection in the bursa. Runner's knee (chondromalacia patella) is characterized by pain under the kneecap, especially during activities like running, but it does not usually present with a distinct fluid collection. Therefore,