Elbow
The elbow is a complex hinge joint in the arm that enables bending, straightening, and rotation. It connects three primary bones: the humerus, radius, and ulna, and is supported by various muscles, ligaments, and cartilage. The triceps and biceps are crucial muscles that facilitate the elbow's movement, allowing it to extend and flex respectively. The joint is stabilized by three key ligaments: the medial collateral ligament, the annular ligament, and the lateral collateral ligament, which help maintain its structure and flexibility. Although the elbow is less prone to dislocation than other joints, injuries such as ligament tears, tendon damage, or fractures can significantly impair its function and cause pain. Cartilage, which cushions the bones, plays a critical role in reducing friction during movement and protecting the joint from wear and tear. Proper functioning of the elbow is essential for performing everyday tasks, making understanding its anatomy and potential injuries important for overall arm health.
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Subject Terms
Elbow
The elbow is a joint that allows the arm to bend and straighten. It is composed of three primary bones, two primary muscles, and several ligaments. Supporting muscles smooth and stabilize the movement of the elbow, while tendons and ligaments secure the parts of the elbow to their proper locations.
Elbows have a great deal of supporting structure, making them more resistant to dislocation than other joints. Tears in ligaments and tendons and damage to the various muscle groups and bones controlling the elbow can be very painful. Tendon and ligament injuries may require surgery to properly heal. Hyperextending the elbow can injure its various supporting structures.
Background
The elbow is a versatile, complex joint. It allows the arm to extend, bend, and rotate. The muscles involved in the elbow's movements have a major effect on the movement of the wrists and fingers. Any injury to the elbow can impair a person's ability to carry out common daily tasks.
The elbow is a hinge joint. Hinge joints move a limited distance in a single direction. The muscles that allow the elbow to bend as a hinge, however, also allow the forearm and wrist to rotate. Some joint types, such as ball-and-socket joints, allow a greater degree of movement than hinge joints do. Ball-and-socket joints, such as the shoulder, can move vertically and horizontally and can rotate in several directions. Unlike the elbow, however, these joints are more easily dislocated or injured.
Overview
The elbow joint connects three bones: the humerus, the radius, and the ulna. The humerus is the bone that supports the upper half of the arm. It widens near the elbow, forming two protrusions called epicondyles. These provide a place for the muscles and ligaments to attach.
The lower arm is composed of two bones that form a bow shape. The thicker bone, the ulna, connects directly to the humerus. The thinner bone, the radius, is attached to the humerus by connective tissue.
The tissue that connects one bone to another is called a ligament. Ligaments are found throughout the entire human skeleton. Ligament tissue is tough, stretchy, and designed to increase the flexibility of a joint while reducing damage to the bone.
The elbow joint contains three primary ligaments. The medial collateral ligament connects the inside of the ulna to the elbow joint. It is divided into two sections. The anterior, or front section, and the posterior, or back section. The medial collateral ligament passes over the elbow joint and binds the ulna to it. The annular ligament connects the radius to the humerus, giving the bone a small degree of flexibility. The lateral collateral ligament connects the annular ligament to other ligaments, helping to reinforce it and increase its flexibility.
While bones give a joint structure and ligaments give it flexibility, muscles make a joint move. The elbow is a complicated joint that requires many muscles to allow its full range of motion. The triceps brachii muscle, often called the triceps, is a large muscle that stretches along the back of the humerus. When the triceps contracts, it pulls the arm bones into a straight line, extending the elbow. The biceps brachii, often called the biceps, is a large muscle that stretches along the front of the humerus. It performs the opposite function of the triceps. When the biceps contracts, it pulls the ulna and radius toward the humerus, causing the elbow to bend.
Several muscles in the elbow joint combine to allow the ulna and radius to rotate. The brachialis, which wraps around the elbow joint, allows the arm to rotate so that the palm faces upward. The brachioradialis helps keep the elbow stable while it bends. The extensor carpi radialis brevis helps the wrist extend, while the pronator teres helps stabilize the forearm while it rotates.
The muscles in the elbow are attached to the bone by tendons. Tendons are tough, flexible, and made of a material similar to ligaments. Healthy tendons maximize the strength of muscles, pulling the bone along as the muscle contracts. The biceps tendon allows the elbow to bend effectively, while the triceps tendon allows the elbow to straighten effectively.
In complex joints like the elbow, hard parts of the bone can rub against each other during movement. If this rubbing continues unchecked, it can damage bones, causing pain whenever the joint is used. To prevent this, the body produces a substance called cartilage. This firm, white substance coats the ends of bones. It helps lubricate joints, reducing friction and preventing the ends of bones from experiencing wear and tear. Cartilage acts as a cushion against impacts to joints. Rather than allowing the bone to absorb the full impact, cartilage compresses to soften the impact.
The function of the elbow can be impeded by a few injuries. If ligaments in the elbow are damaged, the elbow will lose its stability. It will bend in unexpected, sometimes damaging ways. Ligament injuries can cause dislocation of the elbow, which is when the elbow joint moves drastically out of place.
If tendons are torn, the elbow will lose its ability to straighten or bend. This can be exceptionally painful and may require surgery to repair. Cracks or breaks in the humerus, ulna, or radius near the elbow can impede elbow function.
Damage to cartilage around the elbow joint can cause numerous injuries. Cartilage can become damaged during a dislocation when bones begin moving in unexpected or incorrect ways. It can degenerate over time due to the aging process. Cartilage damage can cause instability, inflammation, stiffness, and pain. Because of the large amount of muscles and ligaments supporting the joint, however, the elbow is less susceptible to cartilage damage than most other joints.
Bibliography
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