A lump in the elbow joint may be caused by subcutaneous tissue hyperplasia, osteoarthritis, gout and so on. 1. Hyperplasia of subcutaneous tissue: elbow joint belongs to composite joint, there is abundant subcutaneous tissue covering around the joint, which protects the normal movement of the joint. When the subcutaneous tissue of elbow joint has abnormal hyperplasia or accumulation, swelling of elbow joint may appear, such as lipoma caused by accumulation of subcutaneous fat, fibroma caused by fibrous hyperplasia, and sebaceous cyst caused by sebaceous gland blockage. 2. Osteoarthritis and gout: when the elbow joint has degenerative lesions leading to osteoarthritis, osteophytes can appear, and the formation of bone capillaries, which may also be manifested as a lump in the elbow joint; when synovitis and increased joint fluid are present, intra-articular cysts may appear, which may also manifest the above symptoms; when combined with gout, gout stone may be formed due to the deposition of uric acid crystals, which may also be manifested as a lump in the elbow joint. There may also be other reasons for the elbow joint lump, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.