Differential Diagnosis for a "Squigly" Feeling Like a Giant Vein at the Knee Cap

• Single Most Likely Diagnosis
  • Varicose vein: This is the most likely diagnosis given the description of a "giant vein" feeling at the knee cap. Varicose veins are enlarged, twisted veins that can be felt under the skin and are common in the legs.
• Other Likely Diagnoses
  • Phlebitis: Inflammation of a vein, which could cause a vein to feel enlarged or tender, similar to a varicose vein.
  • Hematoma: A collection of blood outside of blood vessels, which could feel like a lump or swelling under the skin, potentially near a vein.
  • Lymphatic malformation: An abnormal formation of lymphatic vessels that could cause swelling or a feeling of a lump under the skin.
• Do Not Miss Diagnoses
  • Deep Vein Thrombosis (DVT): A blood clot in a deep vein, which can be life-threatening if it breaks loose and travels to the lungs. Although less likely given the description, it's crucial to consider due to its potential severity.
  • Popliteal aneurysm: An abnormal dilation of the popliteal artery, which runs behind the knee. Although rare, it's a serious condition that could present with a pulsatile mass near the knee.
• Rare Diagnoses
  • Arteriovenous malformation (AVM): An abnormal connection between arteries and veins, which could cause a variety of symptoms including a feeling of a large vein or swelling.
  • Vascular tumor: A rare tumor of the blood vessels, which could present as a lump or swelling under the skin, potentially feeling like an enlarged vein.