A ganglion cyst is a fluid-filled bump associated with a joint or tendon sheath. They most often occur at the back of the wrist followed by the front of the wrist. Onset is often over months. Typically there are no further symptoms. Occasionally pain or numbness may occur. Complications may include carpal tunnel syndrome.
The cause is unknown. The underlying mechanism is believed to involve an outpouching of the synovial membrane. Risk factors include gymnastics. Diagnosis is typically based on examination with light shining through the lesion being supportive. Medical imaging may be done to rule out other potential causes.