A lump on the inside of the wrist may be a tendon sheath cyst or lipoma. 1. Tendon sheath cysts: tendon sheath cysts occur on the back of the hand and foot, due to the increase of mucus in the joints or tendon sheaths and protrudes on the surface of the skin, it is a benign lump, generally associated with injuries, long-term engagement in joints and heavy physical labor, overstrain, but also with the low immune system has a certain relationship, you need to go to the hospital to squeeze through the cysts and inject drugs or surgical resection. 2. Lipoma: generally related to genetic factors or environmental factors, the specific cause is not clear, if the lump is not painful, itchy can not be too concerned, if there is other discomfort, it is recommended to go to the hospital for surgical resection. There may be other reasons for the bag on the inside of the wrist, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment.