The elbow is a complex joint formed by the articulation of three bones – the humerus, radius and ulna. The elbow joint helps in bending or straightening of the arm to 180 degrees and assists in lifting or moving objects.
The bones of the elbow are supported by:
The elbow joint is formed at the junction of three bones:
The Humerus (upper arm bone) forms the upper portion of the joint. The lower end of the humerus divides into two bony protrusions known as the medial and lateral epicondyles which can be felt on either side of the elbow joint.
The Ulna is the larger bone of the forearm located on the inner surface of the joint. The curved shape of the ulna articulates with the humerus.
The Radius is the smaller bone of the forearm situated on the outer surface of the joint. The head of the radius is circular and hollow which allows movement with the humerus. The connection between the ulna and radius helps the forearm to rotate.
Humeroulnar joint is formed between the humerus and ulna and allows flexion and extension of the arm.
Humeroradial joint is formed between the radius and humerus, and allows movements like flexion, extension, supination and pronation.
Radioulnar joint is formed between ulna and radius bones, and allows rotation of the lower arm.
Articular cartilage lines the articulating regions of the humerus, radius and ulna. It is a thin, tough, flexible, and slippery surface that acts as a shock absorber and cushion to reduce friction between the bones. The cartilage is lubricated by synovial fluid, which further enables the smooth movement of the bones.
There are several muscles extending across the elbow joint that help in various movements. These include the following:
The elbow joint is supported by ligaments and tendons, which provide stability to the joint.
Ligaments are a group of firm tissues that connect bones to other bones. The most important ligaments of the elbow joint are the:
Tendons are bands of connective tissue fibers that connect muscle to bone. The various tendons which surround the elbow joint include:
The main nerves of the elbow joint are the ulnar, radial and median nerves. These nerves transfer signals from the brain to the muscles that aid in elbow movements. They also carry the sensory signals like touch, pain, and temperature back to the brain.
Any injury or damage to these nerves causes pain, weakness or joint instability.
Arteries are blood vessels that carry oxygen-pure blood from the heart to the hand. The main artery of the elbow is the brachial artery that travels across the inside of the elbow and divides into two small branches below the elbow to form the ulnar and the radial artery.
The elbow joint is a hinge joint that provides great stability and movement for performing daily activities. The strong muscles that extend across the elbow joint bring about actions like flexion, extension, supination and pronation enabling us to perform activities of daily living. These activities can be impaired if there is an injury or trauma to the elbow.