Differential Diagnosis for 13-year-old Female with Knee Pain, Swelling, and Redness
Single Most Likely Diagnosis
- Juvenile Idiopathic Arthritis (JIA): This is a common cause of knee pain and swelling in adolescents without a history of trauma. The elevated CRP supports an inflammatory process, which is consistent with JIA.
Other Likely Diagnoses
- Septic Arthritis: Although the patient does not have systemic symptoms, septic arthritis can present with localized signs of infection such as pain, swelling, and redness. The elevated CRP increases the suspicion for a septic process.
- Osgood-Schlatter Disease: This is a common cause of knee pain in adolescents, especially during periods of rapid growth. However, it typically presents with pain and swelling below the knee and is often associated with activity.
- Patellofemoral Pain Syndrome: This condition is characterized by pain around or behind the patella, often associated with activities that put stress on the knee. It's a common cause of knee pain in adolescents but typically doesn't cause significant swelling or redness.
Do Not Miss Diagnoses
- Lyme Arthritis: Lyme disease can cause arthritis, which may present with knee pain, swelling, and elevated inflammatory markers. It's crucial to consider this diagnosis, especially in endemic areas, as missing it could lead to prolonged morbidity.
- Osteomyelitis: Bone infection can present with localized pain, swelling, and redness, along with elevated CRP. Although less common, it's a serious condition that requires prompt diagnosis and treatment.
- Malignancy (e.g., Osteosarcoma, Ewing's Sarcoma): Although rare, bone cancers can present with pain, swelling, and systemic symptoms like elevated CRP. Missing these diagnoses could have devastating consequences.
Rare Diagnoses
- Rheumatic Fever: This is a rare complication of streptococcal infection that can cause arthritis, among other symptoms. It's less likely but should be considered in the differential diagnosis, especially if there's a history of recent streptococcal infection.
- Sarcoidosis: This condition can cause arthritis and elevated inflammatory markers but is rare in adolescents and typically presents with systemic symptoms.
- Hemophilia or other Coagulopathies: These conditions can cause hemarthrosis (bleeding into the joint), leading to pain, swelling, and potentially elevated inflammatory markers due to the body's response to blood in the joint. However, they are rare and usually have a known family history or previous episodes.