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
- Ligaments and tendons
- Muscles
- Nerves
- Blood vessels
Bones and Joints of the Elbow Joint
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.
The elbow consists of three joints from articulation of the three bones namely:
- Humero-ulnar joint – allows flexion and extension of the arm.
- Humero-radial joint – allows movements like flexion, extension, supination, and pronation.
- Radio-ulnar joint – and allows rotation of the lower arm.
Articular cartilage lines the articulating regions of the humerus, radius, and ulna. The cartilage is lubricated by synovial fluid, which further enables the smooth movement of the bones.
Muscles of the Elbow Joint
There are several muscles extending across the elbow joint that help in various movements. These include the following:
- Biceps brachii
- Triceps brachii
- Brachialis
- Brachioradialis
- Pronator teres
- Extensor carpi radialis brevis
- Extensor digitorum
Elbow Joint Ligaments and Tendons:
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:
- Medial or ulnar collateral ligament: comprised of triangular bands of tissue on the inner side of the elbow joint.
- Lateral or radial collateral ligament: a thin band of tissue on the outer side of the elbow joint.
Together, they hold the humerus and ulna tightly in place during movement of the arm.
- Annular ligament: These are a group of fibers that surrounds the radial head, and holds the ulna and radius tightly in place during movement of the arm.
The ligaments around a joint combine to form a joint capsule that contains synovial fluid.
Any injury to these ligaments can lead to instability of the elbow joint.
Tendons are bands of connective tissue fibers that connect muscle to bone. The various tendons which surround the elbow joint include:
- Biceps Tendon: attaches the biceps muscle to the radius, allowing the elbow to bend
- Triceps Tendon: attaches the triceps muscle to the ulna, allowing the elbow to straighten
Nerves of The Elbow Joint:
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.
Blood vessels:
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.