Elbow Joint Anatomy

The elbow is a complex joint connecting the upper arm to the forearm. It enables essential movements such as bending, straightening, and rotation of the arm. Understanding elbow anatomy helps patients better comprehend their conditions and treatment options.

Bones and Joints of the Elbow

The elbow joint is formed by three bones working together:

• Humerus - The upper arm bone that forms the top portion of the joint. The lower end features two bony prominences (epicondyles) on each side of the elbow.
• Ulna - The larger forearm bone on the inner side, articulating with the humerus to allow bending and straightening.
• Radius - The smaller forearm bone on the outer side with a circular head that enables rotation of the forearm.

These bones form three distinct joints that work in harmony:

• Humeroulnar joint - Allows flexion and extension (bending and straightening)
• Humeroradial joint - Enables flexion, extension, and rotational movements
• Radioulnar joint - Facilitates forearm rotation (turning palm up or down)

Smooth articular cartilage covers the joint surfaces, providing cushioning and reducing friction during movement. This cartilage is lubricated by synovial fluid for smooth, pain-free motion.

Muscles of the Elbow

Multiple muscles cross the elbow joint to provide movement and stability:

• Biceps brachii - Primary muscle for bending the elbow
• Triceps brachii - Extends the arm and stabilizes during fine movements
• Brachialis - Works beneath the biceps to flex the elbow
• Brachioradialis - Assists in flexion and forearm rotation
• Pronator teres - Rotates the forearm to turn the palm downward
• Extensor carpi radialis brevis - Controls wrist extension
• Extensor digitorum - Extends the fingers

Ligaments and Tendons

Ligaments connect bones and provide joint stability:

• Medial (ulnar) collateral ligament - Triangular bands on the inner elbow providing primary stability
• Lateral (radial) collateral ligament - Stabilizes the outer side of the joint
• Annular ligament - Wraps around the radial head, securing proper bone alignment during movement

These ligaments work together to prevent abnormal joint movement and maintain stability during activities.

Tendons attach muscles to bones, enabling movement:

• Biceps tendon - Connects the biceps muscle to the radius for elbow flexion
• Triceps tendon - Attaches the triceps muscle to the ulna for elbow extension

Injury to these structures can lead to pain, instability, and loss of function.

Nerves of the Elbow

Three major nerves pass through the elbow region:

• Ulnar nerve - Travels behind the medial epicondyle ("funny bone")
• Radial nerve - Runs along the outer aspect of the elbow
• Median nerve - Passes through the front of the elbow

These nerves control muscle movement and provide sensation to the forearm and hand. Nerve compression or injury can cause pain, numbness, tingling, or weakness.

Blood Supply

The brachial artery provides the main blood supply to the elbow. This vessel travels down the inside of the upper arm and divides below the elbow into two branches:

• Ulnar artery - Supplies the inner forearm and hand
• Radial artery - Supplies the outer forearm and hand

Adequate blood flow is essential for healing after injury or surgery.