Differential Diagnosis for 14-year-old with Right Knee Tenderness and Edema

Single Most Likely Diagnosis

• Osgood-Schlatter Disease: This condition is characterized by inflammation of the patellar tendon at the tibial tuberosity, leading to pain, swelling, and tenderness in the area. It is common in adolescents, especially during growth spurts, and is exacerbated by activities that involve jumping, making it the most likely diagnosis given the symptoms.

Other Likely Diagnoses

• Patellar Tendinopathy (Jumper's Knee): Similar to Osgood-Schlatter disease, this condition affects the patellar tendon but is more commonly seen in older adolescents and young adults. It causes pain and tenderness around the patellar tendon, which worsens with jumping activities.
• Sinding-Larsen-Johansson Syndrome: This condition is an inflammation of the patellar tendon at its origin on the inferior pole of the patella. It presents with pain and swelling below the kneecap and is also related to overuse or repetitive strain, common in young athletes.
• Tibial Tuberosity Apophysitis: Although less common, this condition involves inflammation of the growth plate at the tibial tuberosity and can cause symptoms similar to Osgood-Schlatter disease.

Do Not Miss Diagnoses

• Tumor (e.g., Osteosarcoma): Although rare, bone tumors can present with localized pain and swelling. It's crucial to consider this possibility to ensure timely diagnosis and treatment if present.
• Infection (Osteomyelitis or Septic Arthritis): Infections in the bone or joint can cause severe pain, swelling, and systemic symptoms like fever. Early diagnosis is critical for effective treatment.
• Fracture (Stress or Traumatic): A fracture around the tibial tuberosity could cause pain and swelling, especially if related to a recent trauma or overuse.

Rare Diagnoses

• Binding-Larsen-Johansson Syndrome with a Patellar Sleeve Fracture: A rare complication where a piece of the bone and cartilage separates from the patella.
• Hoffa's Fat Pad Syndrome: Inflammation of the infrapatellar fat pad, which can cause anterior knee pain.
• Tibial Tubercle Fracture: A rare fracture that can occur in adolescents, often related to a sudden contraction of the quadriceps muscle.

Each of these diagnoses should be considered based on the patient's history, physical examination, and possibly imaging studies to determine the underlying cause of the symptoms.