A large lump on the elbow may be caused by lipoma, epidermal cyst and bursitis. 1. Lipoma: its etiology is not yet clear, may be related to heredity, chronic inflammation and other factors, the patient’s skin will appear single or multiple lumps, commonly found in the neck, shoulder, limbs and other places. 2. Epidermoid cysts: Epidermoid cysts are mainly related to embryonic ectopic, trauma and other factors, most commonly found in the face, upper trunk, etc., the affected area of the skin will appear dome-shaped elevated swellings, nodules. 3. Bursitis: Bursitis may be caused by trauma, infection, and disease that damages the bursa, and the patient will have localized swelling, stiffness, and lumps around the joints. There are many reasons for the elbow to grow a big bag, and it is recommended that the patient consult a doctor for examination to clarify the cause of the disease.