Differential Diagnosis for Severe Right Knee and Calf Pain in a 6 Year Old with No Trauma

Single Most Likely Diagnosis

• Growing Pains: This is a common condition in children, characterized by recurrent leg pain, typically in the calf or thigh, without any underlying serious disease. The pain often occurs at night and can be severe enough to wake the child.

Other Likely Diagnoses

• Osgood-Schlatter Disease: A condition that causes knee pain in children, especially during growth spurts. It is characterized by inflammation of the patellar tendon at its insertion on the tibial tubercle.
• Patellofemoral Pain Syndrome: Also known as runner's knee, this condition causes pain around or behind the patella, often related to activities that put stress on the knee.
• Muscle Strain: Although less common without trauma, muscle strains can occur due to overuse or unusual physical activity.
• Infection (e.g., Osteomyelitis, Septic Arthritis): Though less likely without systemic symptoms, infections can cause severe localized pain and must be considered, especially if there's any sign of infection such as fever or redness.

Do Not Miss Diagnoses

• Deep Vein Thrombosis (DVT): Although rare in children, DVT can cause severe calf pain and swelling. It's crucial to consider this diagnosis, especially if there are risk factors such as recent travel, family history of clotting disorders, or if the child is immobile.
• Malignancy (e.g., Osteosarcoma, Ewing's Sarcoma): Bone cancers can present with localized pain and should be considered, especially if the pain is persistent, worsening, or accompanied by systemic symptoms like weight loss or fever.
• Neurological Conditions (e.g., Peripheral Nerve Entrapment): Conditions affecting the nerves can cause severe pain and should not be overlooked.

Rare Diagnoses

• Legg-Calve-Perthes Disease: A rare condition that affects the hip joint, causing pain that can sometimes be referred to the knee.
• Juvenile Idiopathic Arthritis (JIA): An autoimmune disease that can cause joint pain and swelling, including in the knee.
• Hematological Disorders (e.g., Sickle Cell Crisis): Certain conditions like sickle cell disease can cause severe pain episodes, including in the legs.
• Inflammatory Conditions (e.g., Kawasaki Disease): Although more commonly associated with systemic symptoms, some inflammatory conditions can present with localized pain.