While the elbow is a very complex structure it can be easily visualized through x-rays or MRI for a better understanding of how this structure works. Of course it’s advisable to keep your elbows healthy and treat injuries promptly to prevent joint damage later on too. The elbow is a very versatile joint in the upper extremities that provide a great deal of motion within the arm. Without the elbow many daily activities would be quite impossible. Eating, playing sports, dressing, and hugging our loved ones would all be impossible.
Read on to learn more about the anatomy of your elbow and the many functions this joint can provide on a daily basis.
The Bones of The Elbow
The elbow contains several bones and each has an important job to do. The elbow also has the responsibility of being the connecting point for the radius and ulna to the humerus as well. Below you will find a detailed description of the bones that make up the structure of the elbow.
Radius – The bone of the lower arm extending from the elbow to the wrist.
This bone is located on the side of the arm where the thumb is located.
Ulna – The ulna is a smaller bone that runs through the lower arm connecting with the radius.
This bone lies on the side of the arm where
the pinkie is located.
Humerus – The humerus is the long bone of the upper arm.
This bone originates at the socket of the shoulder and extends to the elbow joint. When connected with
the elbow this bone joins the ulna and radius to form the arm or upper extremity.
Muscles of the Elbow
Of course with bones must be connective tissues and muscles for a complete structure. Without these the elbow would simply be a pile of bones incapable of movement. There aren’t many muscles involved in the movement of the elbow, but their work is phenomenal. From performing great tennis serves to cuddling a new born baby, these muscles are hard workers with great results. Keeping them healthy and avoiding repetitive injury to these areas will help them stay stronger, longer. The two major muscles of the elbow are listed below along with their definitions to help you better understand their function.
Biceps Brachii – This is a very large muscles that is present in the upper arm.
This muscle helps to rotate the arm and is responsible for the ability to place our palms up.
Triceps Brachii – This muscle originates in the back area of the upper portion of the arm and helps to stabilize the hand when the need for fine motor skills arises.
Nerves of the Elbow
There are also three major nerves that pass through the elbow as well and innervate the muscle contractions within the upper and lower arm. These nerves terminate in the hand after passing through the wrist. The following are the major nerves that pass through the elbow and their definitions:
*The nerves as they innervate the elbow muscles
Median Nerve –The median nerve forms the junction of the lateral medial cords. It travels lateral to the brachial artery to approximately the mid humerus or junction of the proximal two thirds to distal one third of the humerus. At this level, the median nerve crosses over the brachial artery to lie in a more medial anatomic position.
The nerve is superficial to the brachialis muscle and usually lies in a groove with the brachial artery, between the brachialis and biceps muscle. It travels across the antecubital fossa, underneath the bicipital aponeurosis, and between the biceps tendon and the pronator teres. At this level, the median nerve is on the distal aspect of the brachialis muscle. The nerve then travels underneath the 2 heads of the flexor digitorum sublimis (FDS) muscle to lie between this muscle and the flexor digitorum profundus (FDP) muscle. The median nerve emerges between these 2 muscles in the distal forearm to then travel ulnar to the flexor carpi radialis and radial to the sublimis tendons, usually directly underneath the palmaris longus tendon, and enters the carpal tunnel in a more superficial plane to the flexor tendons.
The motor branch emerges at variable sites but most frequently at the distal aspect of the carpal ligament to service the thenar musculature. Just beyond the end of the carpal ligament, the median nerve trifurcates to become the common digital sensory nerves to the fingers. The palmar cutaneous branch of the median nerve is a sensory branch that comes from the main body of the nerve approximately 6 inches above the rest of the nerves and services an elliptical area at the base of the thenar eminence. This superficial nerve does not lie within the carpal tunnel.
Just distal to the antecubital fossa, the median nerve branches into the anterior interosseous nerve, which travels on the interosseous membrane and innervates the flexor pollicis longus (FPL), the FDP to the radial 2 digits, and the pronator quadratus at its termination. The nerve innervates the pronator teres, flexor capri radialis, the FDS, and the 2 radial FDP tendons. It also supplies the FPL and the pronator quadratus.
Within the hand, the motor branch of the median nerve supplies the opponens pollicis, the flexor pollicis brevis, and the abductor pollicis brevis musculature. It also supplies the 2 radial lumbrical muscles in the hand. The median nerve supplies sensation to the 3.5 digits on the radial aspect.
In short: This nerve can be found on the inside of the arm passing by the front side of the elbow. The median nerve provides impulses to bend the wrist and hand. It also provides sensation to the hand, thumb, index, and middle fingers. An injury to this nerve may cause carpal tunnel syndrome.
Ulnar Nerve –The ulnar nerve arises from the medial cord of the brachial plexus. The ulnar nerve travels posterior to the brachial artery and remains within the flexor compartment of the upper extremity until it reaches the medial epicondyle. The nerve travels behind the medial epicondyle back into the flexor compartment underneath the flexor musculature. Above the elbow, the ulnar nerve lies on the long head and then the medial head of the triceps muscle, directly posterior to the medial intermuscular septum between the brachialis and the triceps muscles.
The fascial bands over the median nerve constitute the Struthers arcade. The nerve passes within the cubital tunnel posterior to the medial epicondyle. It is directly underneath a tight fascial roof known as the Osborne band, which is contiguous with the leading fascial heads of the flexor carpi ulnaris (FCU) muscle. Just above the elbow branches, the nerve branches to the superficial head of the FCU. The nerve lies directly over the top of the FDS muscle and beside the FDP muscle at the elbow.
As the ulnar nerve travels down the forearm, it is wedged between the FDS and the FDP muscle bellies to exit in the distal forearm just ulnar to the ulnar artery and the FDP tendons. The FCU tendon protects the nerve on its ulnar aspect. The ulnar nerve travels within the Guyon canal at the wrist to supply the hypothenar muscles, including the opponens digiti quinti and the abductor digiti quinti. It also supplies the 2 ulnar lumbrical muscles and the interossei to the hand and the deep branch to the flexor pollicis brevis muscle. The ulnar nerve supplies sensation to the 1.5 digits of the ulnar aspect. The dorsal cutaneous branch of the ulnar nerve supplies sensation to the dorsal ulnar half of the hand and fingers. This nerve arises from the main ulnar nerve approximately 6 cm proximal to the wrist.
In short: This nerve can be found on the inside of the arm and positioned behind the back of the elbow as well. This nerve also allows the fingers and wrist to bend while also allowing the fingers lateral motion. The nerve supplies feeling to the back of the hand, the palm, and the ring fingers as too.
Radial Nerve –The radial nerve emerges from the posterior aspect of the humerus in the spiral groove between the brachialis and brachioradialis muscles above the elbow. It leaves the extensor compartment to travel in front of the elbow underneath the brachioradialis muscle, sending branches of innervation to it just above the elbow. The radial nerve divides at the level of the radial capitellar joint into the deep motor branch of the radial nerve (ultimately becoming the posterior interosseous nerve) and the superficial radial nerve. At this point, it branches to the extensor carpi radialis brevis.
The superficial radial nerve continues to travel underneath the brachioradialis muscle to ultimately emerge between that muscle and the extensor carpi radialis longus tendon. The superficial radial nerve supplies sensation to the radial half of the dorsum of the hand. The deep motor branch of the radial nerve travels within the fat pad and runs below the supinator muscle to emerge the supinator and become the posterior interosseous nerve in the distal dorsal aspect of the forearm. The posterior interosseous nerve travels at the level of the interosseous membrane to ultimately provide sensation to the posterior aspect of the wrist. This nerve innervates the extensor indicis proprius, extensor digiti quinti, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis brevis, and extensor digitorum communis muscles.
In short: The radial nerve can be found along the back and the outer portions of the upper arm. This nerve allows for the straightening of the wrist, hand, and thumb. It also supplies feeling to the back of the hand, index finger, a portion of the ring fingers, and the index finger.