Dorsal tendon sheath cyst is mainly due to the dorsal part of the metatarsophalangeal joints, due to trauma, strain injury and other triggers lead to joint capsule damage rupture, synovial cavity synovial fluid from the rupture outflow, resulting in local wrapped, cystic swelling, the contents of translucent jelly-like tissue, is a benign lesion, the specific causes may be related to the following factors: 1, foot trauma, due to trauma caused by local tendon sheath injury, bruising and oozing does not fully recover or inflammation gradually formed. 2, local chronic strain injury, due to prolonged standing or prolonged walking, resulting in local tendon sheath chronic injury, aseptic inflammation occurs. The exudate is not fully recovered, or the inflammation is left behind to gradually form tendon sheath cysts.2. Local chronic strain injury, due to prolonged standing or prolonged walking, resulting in chronic injury to the local tendon sheath, aseptic inflammatory reaction occurs, and the exudate gradually increases and is limited to form tendon sheath cysts.3. Bacterial infections around the local tendon sheaths, and inflammatory substances are not completely eliminated to stimulate the periphery of the tendon sheaths to parcel out the formation of tendon sheath cysts.4, Local arthritis is also a common cause of tendon sheath cysts.