Differential Diagnosis for Anterior Knee Pain in a 12-year-old Boy

Single most likely diagnosis

• Osgood-Schlatter disease: This condition is characterized by inflammation of the patellar tendon at the tibial tuberosity, typically occurring in adolescents involved in sports that include frequent running or jumping. The patient's symptoms of anterior knee pain worsening with activity and improving with rest, along with tenderness and swelling over the tibial tuberosity, are classic for Osgood-Schlatter disease.

Other Likely diagnoses

• Patellofemoral pain syndrome: This condition is common in adolescents and is characterized by pain around or behind the patella, often associated with activities that put stress on the knee, such as running, jumping, or climbing stairs. While the primary complaint is usually around the patella, the involvement of the knee in sports and the nature of the pain could suggest this diagnosis.
• Sinding-Larsen-Johansson syndrome: This is another condition that affects the knee in adolescents, involving the patellar tendon at its origin on the inferior pole of the patella. It presents with pain and swelling below the kneecap, similar to Osgood-Schlatter disease but at a different location.

Do Not Miss diagnoses

• Tibial tuberosity fracture or avulsion fracture: Although less common, a fracture or avulsion at the tibial tuberosity could present with similar symptoms, including pain and swelling. Missing this diagnosis could lead to improper healing and long-term complications.
• Infection (osteomyelitis or septic arthritis): While rare, infection in the bone or joint could present with pain, swelling, and tenderness. This diagnosis is critical to identify promptly due to the potential for serious complications, including destruction of the joint or bone.

Rare diagnoses

• Tumor (e.g., osteosarcoma): Bone tumors are rare but could present with localized pain and swelling. They are more commonly seen in older adolescents or young adults but should be considered in the differential diagnosis to ensure early detection and treatment.
• Rheumatologic conditions (e.g., juvenile idiopathic arthritis): These conditions can cause knee pain and swelling and, although less likely given the specific location and activity-related nature of the pain, should be considered in a comprehensive differential diagnosis.