Of all the joints in the human body, elbow joint is the one that is used most often to perform day-to-day activities. It is a hinge joint, and is designed such that, it allows two types of movements - flexion and extension. Flexion is the position in which, the arm is bent, while extension is the position in which the arm is straight.
Elbow anatomy comprises the bones, muscles, tendons, ligaments, nerves, and blood vessels. All these components act as stabilizers to the elbow joint and help it to remain in its plane. To understand the anatomy of this vital joint, we need to understand the function of each of the aforementioned components.
Bones and Joints
The elbow joint is made up of 3 bones - the humerus (upper arm bone), the radius (thumb side of the forearm), and the ulna (little finger side of the forearm). It is actually a group of 3 separate joints encapsulated in a loose bag called 'joint capsule'. The ulna and humerus articulate with one another to create the elbow joint called ulnohumeral joint.
They are responsible for producing flexion and extension of the arm. The radius and ulna join at the elbow forming a superior radioulnar joint. In this joint, the radius rotates against the ulna allowing the movement of the forearm, called pronation and supination.
An example of pronation and supination is turning of a doorknob. Radiohumeral joint is formed by the articulation of radius and humerus.
Main ligaments supporting the elbow joint are:
Medial Collateral Ligament
It is also known as the Ulnar Collateral Ligament, and comprises two triangular bands, anterior and posterior. These two sections arise from the medial epicondyle, and pass over the inside of the joint.
The anterior portion attaches itself to the front part of the top of the ulna, known as the coronoid process, while the posterior part connects to the back of the ulna, or olecranon process.
Lateral Collateral Ligament
It is also known as the radial collateral ligament, and is a short, narrow band, which passes from the base of the lateral epicondlye to the annular ligament.
It is a band of fibers, which encircles the head of the radius, maintaining a contact between the radius and humerus.
There are several muscles surrounding the elbow joint. The two muscles mainly responsible for elbow flexion and extension are triceps and biceps. Biceps is found on the front of the upper arm, while triceps is found on the back of the upper arm. Apart from these, the other muscles at the elbow include the wrist flexors and extensors.
Elbow is surrounded by several important tendons. The biceps tendon attaches the large biceps muscle on the front of the arm to the radius, so as to allow the elbow to bend with force. The triceps tendon is the large tendon that connects the large triceps muscle with the ulna. It allows the elbow to straighten with force during a push-up.
The radial nerve, the ulnar nerve, and the median nerve are the three main nerves that begin together at the shoulder, and pass through the elbow. These nerves carry signals from the brain to the muscles that are responsible for moving the arm. They also carry signals about sensations like touch, pain, and temperature, back to the brain.
Blood vessels travel along with the nerves to supply the arm with blood. The largest artery in the elbow region, is the brachial artery, which travels across the front crease of the elbow. This artery splits into two branches - the ulnar artery and the radial artery, just below the elbow.
Thus, the elbow is more than a simple hinge. It is designed to provide maximum stability, when we position our forearm to use our hand. We need to place our hands in all the possible ways while performing daily activities.
Hence, daily life can become very hard if the elbow doesn't work well. Understanding the anatomy of an elbow can help us to cope with common injuries related to elbow, like, tennis elbow and elbow pain.