Your body contains almost 400 different joints. The elbow joint is one of the most well-known and is a key part of your arm, hand, and finger movement.
Elbow Function
Your elbow is the place where the bone of the upper arm meets the bones of the lower arm. Your upper arm contains one bone, the humorous, which stretches from the elbow to the shoulder. Your forearm has two bones, the ulna and radius, which reach from the elbow to the wrist. The ulna is the bone on the inner part of your arm, and the radius is the bone on the outer part of your arm.
The elbow is often thought of as being a single joint, but it’s actually made up of three separate joints: the humeroulnar joint, the humeroradial joint, and the proximal radioulnar joint. All three joints are synovial joints, meaning that they are lubricated with synovial fluid to allow smooth movement. The ends of the bones within the joint are covered in thick cartilage for shock absorption.
Humeroulnar Joint. The humeroulnar joint is the point where the humerus and ulna meet. It is a hinge joint, so like the hinges of a door, it’s meant to open and close in one direction. Other examples of this type of joint include joints in your knees and knuckles. The humeroulnar joint allows you to bend and straighten your arm.
Humeroradial Joint. The humeroradial joint connects the humerus and the radius. This joint is the combination of a hinge joint and pivot joint. Pivot joints are joints that allow a bone to rotate around a single point. The joint in your neck that allows you to turn your head from side to side is another example of a pivot joint. Like the humeroulnar joint, the humeroradial joint allows you to bend and straighten your elbow, but it also allows you to turn your hand over.
Proximal Radioulnar Joint. The proximal radioulnar joint is a pivot joint. It allows you to rotate your lower arm to a certain degree.
Together, these three joints serve the function of your elbow and lower arm.
Elbow Anatomy
Your elbow needs more than bones and joints to make the arm move. The elbow is also an axis point for many different muscles, ligaments, and tendons.
Elbow Muscles and Ligaments. Several muscles cross over the elbow and the ligaments that support the elbow. These muscles include the:
- Biceps Brachii. The biceps brachii muscle runs along the inside of your upper arm. It originates under the shoulder, attached to the scapula (shoulder blade), and stretches down to the inner elbow. This muscle allows you to turn your forearm.
- Triceps Brachii. The triceps brachii muscle runs along the outside of your arm. It connects to your shoulder blade and the outside of the elbow. This muscle steadies your humerus bone and allows you to extend your forearm and bend your elbow toward your body.
- Brachialis. The brachialis muscle sits under the biceps. It starts about halfway up the humerus on the inside of your arm and reaches down to the inside of the elbow.
The muscles of the lower arm that extend across the elbow include the:
- Brachioradialis. The brachioradialis runs along the outside of your radius. This muscle connects at your humerus just above your elbow and again at the end of the radius at the wrist. This muscle straightens and pulls your lower arm.
- Extensor Carpi Radialis Brevis. The extensor carpi radialis brevis muscle begins at the end of the humerus, running along the side of your radius and attaching to your hand. This muscle helps you move your hand.
- Extensor Digitorum. The extensor digitorum muscle connects to the end of your humerus. It runs across the top of your arm, between the ulna and radius, and branches out to the fingers. This muscle allows you to move your fingers.
Ligaments are tissues that connect bones together. In the elbow, these include the:
- Annular Ligament. This ligament surrounds the base of the radius bone and holds the ulna and radius in place when you use your arm.
- Lateral Collateral Ligament. Also called the radial collateral ligament, this ligament runs along the outside of the elbow.
- Medial Collateral Ligament. Also called the ulnar collateral ligament, this ligament runs along the inside of the elbow.
Elbow Tendons. Tendons are bands of tissue that connect muscle to bones. There are several tendons around the elbow. Two key tendons include the biceps tendon and triceps tendon. The biceps tendon attaches the biceps to the radius so your elbow can bend. The triceps tendon attaches the triceps to the ulna so your elbow can straighten.
Elbow Injuries and Conditions
Elbow conditions and injuries can affect the bones, ligaments, muscles, or tendons within or surrounding the elbow.
Common injuries and illnesses that affect the elbows include:
- Arthritis, a condition in which the joints become swollen and tender. There are many types of arthritis.
- Bursitis, a condition in which a bursa (a small fluid-filled sac that acts as a cushion for bones) becomes inflamed
- Dislocations, a situation in which the end of the bone is forced out of the joint
- Fractures and broken bones occur when something cracks or breaks them
- Sprains, damage to tissues that occurs when ligaments are stretched or torn
- Strains, which are caused when muscles are torn or stretched
Some elbow-specific conditions include:
- Cubital tunnel syndrome, a condition in which the ulnar nerve becomes injured or damaged. This may result in pain, numbness, tingling, or weakness.
- Golfer’s elbow, a condition characterized by damage to the muscles and tendons on the inside of your arm. It’s often caused by repeated stress to these muscles. Golf is one sport that can cause this, but any type of sport that puts repetitive strain on these muscles or ligaments can cause golfer’s elbow.
- Tennis elbow, a condition similar to golfer’s elbow. It affects the tendons and muscles on the outside of your arm as the result of excess strain or overuse. Any type of repetitive activity using these muscles and tendons may cause tennis elbow.
If you’re having issues with persistent pain, numbness, tingling, or weakness in your elbow or arm, speak to your healthcare provider. Proper treatment can help alleviate this pain and prevent potentially permanent damage.