Differential Diagnosis for 7-year-old Female with Left Knee Swelling and Pain
Single Most Likely Diagnosis
- Juvenile Idiopathic Arthritis (JIA): This is a common cause of knee pain and swelling in children, especially in the absence of trauma. The lack of fever, discoloration, and pain with the McMurray test (which tests for meniscal tears) also points towards an inflammatory condition like JIA.
Other Likely Diagnoses
- Osgood-Schlatter Disease: Although more common in adolescents, this condition can occur in younger children. It causes knee pain, swelling, and tenderness below the knee, typically related to activity levels.
- Patellofemoral Pain Syndrome: This condition is characterized by pain around or behind the patella, often related to activities that put stress on the knee, like walking. The absence of pain with the McMurray test and the presence of tenderness to touch support this diagnosis.
- Septic Arthritis (early presentation): Although the child does not have a fever or significant discoloration, early septic arthritis might not always present with these classic signs, especially in young children.
Do Not Miss Diagnoses
- Septic Arthritis: This is a medical emergency that requires prompt diagnosis and treatment to prevent long-term joint damage. Even though the presentation might not be typical, the possibility of septic arthritis cannot be overlooked, especially with any degree of joint swelling and pain.
- Osteomyelitis: Bone infection can present with localized pain, swelling, and tenderness, and it's crucial to consider this diagnosis to initiate appropriate antibiotic treatment.
- Malignancy (e.g., Osteosarcoma, Leukemia): Although rare, these conditions can present with bone or joint pain and swelling. A thorough investigation is necessary to rule out these life-threatening conditions.
Rare Diagnoses
- Hemophilia: If the child has a bleeding disorder, even minor trauma could lead to significant joint swelling and pain due to hemorrhage into the joint space.
- Sickle Cell Disease: Children with sickle cell disease can experience vaso-occlusive crises that lead to joint pain and swelling due to bone infarcts.
- Lyme Arthritis: In endemic areas, Lyme disease can cause arthritis, typically presenting with intermittent episodes of joint pain and swelling, often affecting the knee.