The right foot thumb joint protrudes a pimple to consider the bunion, rheumatoid arthritis, tendon sheath cyst and other factors. 1. Bunion: Bunion is a bone deformity in which the toe of the first metatarsophalangeal joint is shifted to the lateral side. Most of the bunions are related to heredity to a certain extent, and it may also be caused by wearing inappropriate shoes for a long period of time, such as high-heeled shoes and pointy shoes, which leads to bunion deformity and may be accompanied by local pain. 2. Rheumatoid arthritis: rheumatoid arthritis is an autoimmune disease, mainly characterized by invasive arthritis, the onset of the early symptoms of morning stiffness and swelling of the joints, and severe joint deformity, manifested as a protruding thumb joint, accompanied by pain and swelling. 3. Tendon sheath cysts: tendon sheath cysts are benign swellings near the joint ligaments and tendons of the human body, which are considered to be related to the degeneration, injury and long-term stimulation of the adjacent tissues, etc. If the tendon sheaths of the right thumb area appear to be cysts, they will also be manifested as a lump protruding from the thumb joint. The right thumb joint protrudes a lump may also have other causes, it is recommended to go to the hospital in a timely manner to check, according to the cause of the targeted treatment.