Elbow Joint - A Joint With Flexion and Extension Movements
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Elbow Joint : The Joint With Flexion and Extension Movements

Dr.Surya Rao Poodipeddi profile Authored by Dr.Surya Rao Poodipeddi on 29 Apr 2014 - 12:11.
 
There are only two major joints in the human body which move in one direction permitting only flexion and extension namely the elbow and the knee. Joints which permit only flexion and extension movements are known as hinge joints. Elbow joint is one such example of a hinge joint.
Working of elbow joint: It is very simple to understand the working of a hinge joint. Imagine a door which can only be opened or closed but cannot be moved beyond the hinge which facilitates such movements. If any force is exerted to move the door beyond its range the door gives way. There cannot be a better example of a hinge joint than the working of a door.
The elbow joint has only two ranges of movements namely flexion and extension. The forward movement when we bring the hand close to the arm is called flexion. Bringing it back to make the fore-arm and arm straight is called extension movement. However the extension movement over the elbow cannot be carried beyond its limit of straightening up to 180 degrees. Any attempt to accomplish the act beyond this range leads to breakage of the ligaments which hold the components of the joint together.
Opening and closing the door can be compared to acts of extension and flexion of the elbow joint. The door cannot be opened beyond the hinge in as much as the elbow cannot be extended beyond 180 degrees. In case of a door the hinge fixed to the door frame acts as a block. In case of the elbow joint the locking of the bones of the elbow prevent further range of extension.
Having understood the working of a hinge joint, in this case the elbow joint, it is necessary to know how the joint is formed.
Joint Structure: The elbow joint is formed by three bones- the humerus of the arm and the radius and ulna which are the bones of the forearm. To appreciate the positions of radius and ulna it becomes easy if we remember that the bone towards the thumb is known as the radius and the one towards the little finger is called the ulna.
The upper end of the humerus in the arm is associated with the formation of the shoulder joint in combination with other bones. The lower end of the humerus in combination with the upper ends of the radius and ulna forms the elbow joint. The upper ends of the radius and ulna are also involved in the formation of radio-ulnar joint which is the mainstay for the movements of the forearm sideways. The lower ends of the radius and ulna in combination with carpal bones help in the formation of the wrist joint.
The elbow joint is actually formed by the trochlea of the humerus articulating with the ulna and the capitulum of the humerus articulating with the head of the radius. This means that, though there are two sets of articulations there is only one joint capsule and a large bursa to lubricate the joint.
The stability of the elbow joint is maintained by an extensive network of ligaments. These ligaments include ulnar collateral, radial collateral and the annular.
Several muscles originate or insert near the elbow because of which the elbow is a common site for injury.
Common conditions affecting the elbow joint will be discussed in brief in separate article.
*Disclaimer: This is not medical advice. The content is for educational purposes only. Please contact your doctor for any health care issues.