Differential Diagnosis for 4-year-old Girl with Knee Pain
Single Most Likely Diagnosis
- Osgood-Schlatter disease: This is a common condition in children, especially after a traumatic injury, characterized by pain and swelling below the patella. The fact that multiple X-rays were negative for fracture and the patient is still unable to bear weight one week after the injury makes this diagnosis plausible, given its association with overuse or trauma to the knee.
Other Likely Diagnoses
- Patellar tendinitis: This condition involves inflammation of the tendon connecting the patella to the tibia, which could be caused by the knee injury. It would explain the pain below the patella and difficulty bearing weight.
- Medial or lateral patellar retinaculum strain: Strains to the tissues surrounding the patella could cause pain and limited mobility, consistent with the symptoms described.
- Prepatellar bursitis: Inflammation of the bursa in front of the patella could result from a fall onto the knee, leading to pain and swelling in the area.
Do Not Miss Diagnoses
- Infection (septic arthritis or osteomyelitis): Although less likely, an infection in the joint or bone could present with pain and inability to bear weight. It's crucial to consider this diagnosis due to its potential for serious complications if not promptly treated.
- Tumor (e.g., osteosarcoma): While rare, a bone tumor could cause persistent pain and should be considered, especially if the pain is constant and not relieved by rest.
Rare Diagnoses
- Sinding-Larsen-Johansson syndrome: A condition similar to Osgood-Schlatter disease but located at the lower pole of the patella, it's less common and typically associated with overuse rather than a single traumatic event.
- Binding-Larsen-Johansson syndrome variant or patellar apophysitis: Variants of conditions affecting the growth plates around the patella, which could be considered if other diagnoses are ruled out.