What is a likely differential diagnosis for a 16 year-old with knee pain and a prominent tibial tubercle?

Osgood-Schlatter disease is a common condition that occurs during periods of rapid growth, particularly in adolescents who are physically active. The prominent tibial tubercle in association with knee pain in a 16-year-old is characteristic of this condition, which results from traction apophysitis. This occurs when the patellar tendon pulls on the growth plate at the tibial tubercle, leading to pain and swelling in that area. The symptoms are often exacerbated by activities such as running, jumping, or kneeling, which are common in adolescents participating in sports.

The prominence of the tibial tubercle is an important clinical finding because it indicates a chronic condition involving inflammation at the site where the patellar tendon attaches to the tibia. This is distinctly different from growing pains, which are usually more diffuse and not associated with a specific anatomical change. Acute conditions such as ALL would present with additional systemic symptoms like fatigue and bruising, and psychogenic pain lacks identifiable physical findings like the prominent tubercle seen in Osgood-Schlatter disease. Therefore, considering the specific symptoms and the age of the patient, Osgood-Schlatter disease stands out as the most likely differential diagnosis.