The carpal tunnel is a narrow passageway in the wrist made up of ligaments and bones. The median nerve is the main nerve involved in both wrist pain and hand pain. The tendons that connect the muscles of the forearm to the fingers pass through a tightly spaced tunnel that houses the median nerve.

Carpal tunnel syndrome, also known as median nerve entrapment, occurs when swelling or irritation of the nerve or tendons in the carpal tunnel results in pressure on the median nerve.  The median nerve controls sensations to the palm side of the thumb and fingers, as well as impulses to some small muscles in the hand that allow the fingers and thumb to move. This is why carpal tunel symptoms can be thumb pain, wrist pain, hand pain or arm pain.