On the palm side of the hand there are three muscles that move the thumb, they are situated at the base of the thumb. These muscles are called the Adductor pollicis, Abductor pollicis brevis and the Opponens pollicis. The adductor pollicis pulls the thumb inwards, the abductor pollicis brevis moves the thumb away from the hand and the opponens pollicis brings the thumb around towards the palm of the hand to touch the opposite fingers hens the name ‘opponens’.
On the back of the hand there is one muscle called the first dorsal interosseous muscle that assists the adductor pollicis to close the thumb towards the side of the hand. The bulky muscle that can be felt in the first web space.
On the palm side of the thumb there is a group of rope-like tendons that run from the forearm to the tip of your thumb. The Flexor Pollicis Longus and Flexor Pollicis Brevis that gives you the ability to bend the two joints of your thumb down.
On the back of the thumb there are two tendons called the Extensor Pollicis Brevis and Extensor Pollicis Longus that allows you to straighten your thumb. If these tendons are injured you will be unable to straighten your thumb to make the OK or sharp sign.
The Flexor group on the palm side of the thumb is more prone to injury. These tendons gets cut by either glass or a knife. Defending yourself against an incoming knife by shielding yourself with an open hand may lead to your flexor tendon group being severed. Another scenario may be washing dishes and the glass breaks in your hand, or even trying to catch a falling sharp object.
Trigger finger (also known as trigger thumb) is a common phenomenon that involves the flexor tendon running in the thumb. This is when the finger gets stuck in a bent position.
Two branches of nerves give feeling and movement to the thumb. The median nerve supplies the palm side of the thumb and the radial nerve gives feeling to the top side of the thumb.
In most cases nerves are compressed, irritated or injured closer to the wrist, but the dominant pain, burning, shocks, cramps, tingling, pins & needles or any other nerve pain is felt at your fingertips and tip of the thumb.
There is a web of nerves that spreads out over your thumb to give your skin feeling. These digital nerves are always involved when a tendon is severed, which cuts off the sensation to the skin after the laceration.