Outpatient clinics have a high number of patients presenting with small masses in the wrist or ankle, mostly without an obvious cause. Then the most common type of this small mass is a tendon sheath cyst. What is a tendon sheath cyst? A tendon sheath cyst is a cystic swelling that occurs within the tendon sheath of the joint, a condition caused by degeneration of the connective tissue surrounding the joint capsule. They contain a thick, clear, colorless or orange, yellowish mucus and are most often found on the back of the wrist and the back of the foot. Patients are mostly young adults, with women being more common. What causes tendon sheath cysts: There is no direct cause, but it is generally considered to be related to strain. Some occupations that require long-term repetitive strain on the joints such as typists, cargo handling or industries that require long hours of computer operation can trigger or aggravate this condition. What is the manifestation of tendon sheath cyst: The clinical manifestation is mainly a joint mass, usually 1.5*2.0 cm in size, without obvious pressure pain, sometimes the patient feels soreness and discomfort due to tendon activity. On examination, a round mass with smooth shape and clear border can be felt, and the skin on the surface can be pushed without adhesions. Most of the cysts are tense and the masses are tough, a few are soft, but all are cystic in nature. Ultrasound examination can help to determine the nature of the mass. How to deal with tendon sheath cysts: 1.Tendon sheath cysts are treated by squeezing or pounding to make the tendon sheath cysts rupture and gradually absorb on their own, but the recurrence rate is high after treatment. 2, the use of puncture to extract the cyst fluid, or to inject adrenocorticotropic hormone or hyaluronidase, but the recurrence rate after treatment is also high. 3.Surgical removal of the tendon sheath cyst.