Each of your hands has four fingers – the index, middle, ring, and small fingers. The fingers move in two main ways: flexion and extension. We flex our fingers to grab and hold onto objects and extend our fingers to reach out for things.
Patients use many terms for finger flexion:
- making a fist
- folding the fingers
The flexor muscles on the palm side of the forearm form into flexor tendons which run into the palm and attach to each finger. When the muscle fires, the attached tendon pulls its finger into a curled, flexed position into the palm.
Usually, each finger joint can be controlled individually – you can bend the distal joint (at the finger tip) and the proximal joint (in the middle of the finger) separately. When all the finger flexor muscles and tendons pull together, you make a tight fist.
Try this at home!
One cool anatomy fact is that the flexor tendons that move the small, ring, and middle finger usually have a single, common muscle where they start from. You can see this if you try to bend these fingers individually, without moving the other fingers. Try it on your own hand without touching your other fingers! The adjacent fingers move with the finger you’re trying to flex, because they’re connected higher up in the forearm.
Terms like straighten out, point, stretch out, and spread out are used to describe extension of the fingers.
Extensor tendons attach on the top, or back side of the fingers. As the extensor muscles fire, their tendons pull on the finger bones to straighten them out.
The muscles that make the fingers extend are on the back side of your forearm. A perfectly straight finger might be called a finger “in full extension”, but some finger joints extend past zero degrees – this is called hyperextension. Some degree of hyperextension can be normal, but it’s also a term that describes an injury, when the finger is “bent back” and dislocates or fractures.
The thumb is responsible for 50% of the function of our hands. It moves in unique ways compared with the fingers.
The thumb has two joints at the end and middle which flex and extend, just like the fingers. The next joint down, however, is highly specialized and allows several unique movements not possible in the fingers. I’ll discuss the following motions:
Circumduction is the technical term for “moving around in a circle”. This motion occurs at the carpometacarpal joint of the thumb, at the thumb base. This joint is commonly affected by arthritis.
Abduction and adduction are used to describe the thumb’s motion out of and into the palm, respectively. Abduction helps you get your hand around large objects, like a jar of peanut butter or a two liter bottle.
Retropulsion is the technical term for “lifting the thumb off a table while keeping the hand flat”. This motion is created by the extensor pollicis longus tendon.
The wrist joint flexes and extends, but also radially and ulnarly deviates (moves from side to side). The word radially just means “toward the thumb side”. The term ulnarly means “toward the pinky side”. You might use this motion when swinging a hammer.
The distal end of the forearm, where the radius and ulna bones meet, is held together by strong ligaments. The main motion in this location is pronation (turning the hand palm-down, like when you type) and supination (turning the hand palm-up).
Sometimes patients will have more pain with the extremes of supination versus pronation; one hurts worse than the other.
One group of muscles controls flexion and pronation (called the flexor-pronator group) and another group controls extension and supination (called the extensor-supinator group).
Tennis elbow usually involves pain in the outside part of the elbow where the extensor-supinator group attaches. Golfer’s elbow usually involves pain on the inner surface of the elbow, where the flexor-pronator group starts as a tendon and turns into muscle.
Utility and Application
Let’s look at a good example of how an accurate description of pain with a particular motion can be helpful.
Hey, doc – I have pain on the ulnar side of my wrist when I pronate and supinate but not when I flex and extend.
Not only does this tell me where the pain is, but leads even further to an accurate diagnosis because the specific movement that causes pain is described. Additionally, I might recommend one type of wrist splint over the other just based on which particular motion causes pain on the ulnar side of the wrist.
One of my previous articles discusses the concept of the terms radial and ulnar, if you haven’t read that one.
This video on finger, thumb, and wrist motion will help you visualize the concepts I just explained.