conditions
Anatomy
Bones and Joints
There are many bones and joints in the hand, wrist and forearm which work together to allowing us to perform many complex movements. The bones are positioned and stabilized by the ligaments surrounding the joints, and the joints are able to move by the action of muscles and tendons.
The digits are made up of three joints: the metacarpal joint (your knuckle), the proximal interphalangeal joint (middle joint of finger) and the distal interphalangeal joint (the end joint in the finger). You will hear professionals refer to these as MCPs, PIPs and DIPs. The bones at palmar level are called the metacarpals.
The wrist is made up of eight small bones: the scaphoid, lunate, triquetrum, pisiform, hamate, capitate, trapezoid and trapezium. These bones are all different shapes, are arranged in two rows and are stabilised with ligaments. They form the connection between the forearm and the hand, and all move in different directions during wrist action.
The forearm has two long bones, the radius and the ulna. These connect the wrist to the elbow and rotate around each other to allow the hand to be turned palm up and palm down (for example holding the hand out with the palm facing up to receive change).
Muscles and Tendons
Muscles acting to move the hand are divided in to two types; those that are based inside the hand (intrinsic) and those that are based outside the hand (extrinsic).
Strong muscles in the forearm (extrinsic) become tendons that cross the wrist and insert on to bones at wrist level, in the middle of the hand and to the fingers and thumb. When these muscles contract, they cause the bones to move at specific joints.
The small muscles inside the hand (intrinsic muscles) work with the extrinsic muscles to create specific movements, such as making the fingers spread in to a star shape (abduction and adduction), or making the thumb meet the finger tips (opposition). The intrinsic muscles are vital for maintaining stability during movement of the hand, during functional grip and activities requiring fine manipulation and dexterity.
Nerve and Blood Supply
The nerves, that extend from the neck into the upper limb, supply the muscles and the sensory system for the arm. There are three nerves extending into the hand. The ulnar nerve supplies the little finger side of the hand. The median nerve supplies the palmar surface of the thumb side of the hand and the radial nerve supplies the back of the hand.
The blood supply in the hand comes from the radial and ulnar arteries.
Hand Function
The hand is a complex structure which enables us to manipulate objects of enormous diversity in size and shape. In order to be able to do this, the hand works in patterns of movement to form a variety of grips. It is only possible to be fully functional once these skills have developed (during the first few years of life) and if we are able to use all the different grip types available to the human hand.
The following examples of grips are commonly used in daily living:
- Power Grip
such as holding the handle of a broom or a hammer - Span Grip
using the tips of the fingers to grasp around an object such as a large dial - Pinch grip
used in a variety of ways to hold small objects such as picking up a piece of pasta and writing - Lateral key pinch
used for holding and turning keys - Hook grip
for carrying the shopping bags home - Spherical Grip
for throwing and catching balls
Additionally, the hand is only able to function effectively if sensation is intact.
Finally, it must never be forgotten that the hand is an important tool of expression in non verbal communication. We use the hand for gesture and touch. Both of these are vital, and often overlooked, components of daily living.
For diagrams showing the bones and joints of the hands and some basic terminology, including movements, please visit: www.assh.org
For appointments or to contact the consultants please telephone us on
020 7483 5090
