Anatomy of the Elbow
Most of us take for granted the use of our arms and how critical a role our elbows play in our day-to-day activities. The elbow is one of the joints we use most. Its anatomy includes many components—including bones, ligaments, tendons, muscles and nerves— working together to maintain the activities of the arm. Any one of these parts can become injured, throwing us off our game.
Elbow Anatomy: All the Working Parts
The elbow joint is part of a “joint team” that includes the shoulder and wrist joints. The arm joints collaborate to provide your arm’s range of motion and dynamic movements. The elbow is encased in a protective sac called a joint capsule, which cushions the elbow with naturally lubricating gel called synovial fluid.
Elbow Joint Anatomy
The elbow is a hinge, but it isn’t just a single joint. It’s actually comprised of three different bones and three different joints.
Three bones meet at the elbow:
- Humerus: The arm’s largest bone, it joins with and connects to the clavicle and shoulder
- Ulna: This forearm bone extends from the elbow down to the small finger side of the wrist
- Radius: This forearm bone extends from the thumb side of the wrist up to the elbow
Three joints form the elbow:
- Ulnohumeral joint enables movement between the ulna and humerus
- Radiohumeral joint enables movement between the radius and humerus
- Proximal radioulnar joint enables movement between the radius and ulna
Elbow Soft Tissue
Your elbow wouldn’t work at all without the various soft tissues that hold it in place, connect its components, enable its movements, and protect it.
Cartilage provides a smooth gliding surface where bones join, enabling fluid movements.
Bursae, tiny fluid-filled sacs that act as cushiony shock absorbers between tendons and bones, and contain a lubricating synovial fluid. Learn about bursitis, an infection in the bursae
- Bicep: This large muscle at the front of the upper arm provides your elbow with the ability to rotate.
- Tricep: This large muscle at the back of the upper arm powers the extension and straightening of the elbow.
- Brachialis: This muscle, located at the distal end of the humerus, allows you to bend your elbows.
- Wrist flexor and extensors: These forearm muscles attach to both the elbow and wrist and help control flexion and extension of the hand and wrist.
Joints and bones are held together by fibrous, strong, and flexible ligaments. Their cohesive qualities provide stability and prevent injury. The three main ligaments of the elbow include:
- Ulnar collateral ligament (UCL): Located on the inside of the elbow, this major stabilizing ligament connects the humerus and the ulna
- Lateral collateral ligament: Located on the outside of the elbow, this ligament connects the humerus to the radius and plays a major role in elbow extension
- Annular & quadrate ligaments: These ligaments secure the radius bone firmly against the ulna
Tendons are soft tissue that connect muscles to bones to provide support and smooth movement. Tendons connecting in or through the elbow include:
- Biceps tendon: Attaching the biceps muscle to the radius, the biceps tendon aids in rotation of the elbow
- Triceps tendon: This tendon attaches the triceps muscle to the ulna to allow the elbow to straighten
- Lateral & medial epicondyles: You can probably feel two hard “bumps” just above the outside and the inside of the elbow. This is where the wrist extensors and flexors attach to the humerus.
Nerves carry signals between your brain and your elbow and play a key role in pain, touch, hot, and cold sensation – and also help control muscle movement.
The three main nerves of the arm are:
- Radial Nerve
- Ulnar Nerve
- Median Nerve
All three of these nerves originate in the shoulder and extend downward through the elbow and along the arm. The ulnar nerve is the largest and busiest of the three.
The brachial artery is the main artery of the arm and runs along the upper arm and the elbow, where it branches into two smaller arteries:
- Radial artery: This is the larger of the two arteries providing circulation in the lower arm and the one that you can feel when checking your wrist pulse.
- Ulnar artery: The ulnar artery travels right beside the ulnar nerve through the wrists’s Guyon’s canal, providing circulation to the front of the hand, fingers, and thumb.
Because of its prominent role in so many daily activities, the elbow is prone to injury. Common injuries include:
- Tennis elbow: Degeneration of the medial epicondyle that causes inflammation and pain on the outside of the elbow
- Golfer’s elbow: Irritated, inflamed lateral epicondyle causes pain in this condition that usually develops as a result of repetitive motion
- Ulnar collateral ligament (UCL) tears: Painful injuries typically found in sports and occupations that require repetitive overhead movements
- Bursitis: A common and painful infection of the elbow’s bursae