A ganglion is a cyst or sac of fluid that develop around a joint or tendon especially the wrist. It looks like a water balloon attached to a nearby joint capsule or tendon sheath (tissue coating covering tendon). The commonest site for ganglion is the wrist however, it have been seen in almost every joint.

70% of ganglions of the hand are found on the back of the hand. It is called dorsal wrist ganglion. 20% are volar wrist ganglion that appears on the palmar side of the wrist. Other sites include palmar surface of the base of finger or end joint of the finger.

The exact cause of ganglion is still unclear. One theory suggests that it is formed when connective tissue degenerates or damaged by wear and tear. The damaged tissue forms a weakened spot in the joint capsule. The joint fluid escapes through this weakened area and begins to collect in a cyst outside the joint. Over time this cyst grows larger because the joint fluid seems to move out of the wrist joint into the ganglion, but not the other way. In the end, a clear, thick fluid fills the cyst.

A patient with dorsal wrist ganglion may feel a mass on the back of the wrist. With volar wrist ganglion, the bump is felt on the wrist crease below the thumb. The mass may appear suddenly, or develop gradually over time. It may increase or decrease in size. The wrist may ache or feel painful on contact. The ganglion may also interfere with some activities. A volar wrist ganglion may compress the median or ulnar nerve, causing numbness and weakness of movement. A hidden or small occult dorsal wrist ganglion can not be visible or palpable and can be painful and tender to touch. These cysts are not malignant tumour or cancer.
Diagnosis is usually obvious from throughout history and examination by a hand surgeon. In case of occult ganglion, confirmation can be made by simple ultrasound or MRI scan. Occasionally, X-rays of the affected joint is required to look for pre-existing joint arthritis that may give rise to the ganglion.

Treatment for wrist ganglions can be non-surgical or surgical.
Observation is often sufficient for wrist ganglions that are not painful and do not restrict activity. Ganglions typically are harmless and usually do not become worse over time. Treatment is only required if it is enlarging rapidly, causing pain and troubling the patient with his activity.
Ganglion can be treated with needle aspiration. The fluid in the ganglion is syringed out using a sterile needle. This treatment can shrink the cyst and alleviate symptoms. However, the ganglion will invariably reappear. For certain ganglion such as the volar wrist ganglion, aspiration is not encouraged because of the risk of injury to the nearby radial artery.
Surgery is recommended when the patient feels significant pain or when the cyst interferes with activity. The surgery is usually done under a general anesthesia. The ganglion cyst is excised under magnification to avoid injuring adjacent small and vital structures like the nerves and vessels. The whole cyst, the connecting stalk as well as the part of the joint capsule have to be removed in order to reduce the risk of recurrence.

A ganglion may recur after excision. Like any other surgery around the hand, there is a small risk of infection, stiffness of the wrist after the surgery and potential damage to the adjacent nerves and blood vessels.