Elbow Anatomy

The elbow is made up of three bones that join together to form a complex hinge consisting of three separate joints. The upper arm bone, or humerus, connects to the forearm bones, the radius and the ulna, forming the radiohumeral and ulnohumeral joints. The radius and ulna, in turn, form a joint of their own called the radioulnar joint. The entire elbow joint is surrounded by a strong, water tight sac called the joint capsule. This surrounding capsule contains lubricating fluid called synovial fluid. Motion at the elbow includes flexion and extension, rotation of the forearm, and rotatory movement.

Our elbow is held in place and supported by various soft tissues.

Cartilage

Shiny and smooth, cartilage allows smooth movement where two bones come in contact with each other. With the normal wear and tear of age, or with trauma, the cartilage can thin or become damaged causing arthritis.

Tendons

Tendons are soft tissue that connects muscles to bones.

• Biceps Tendon
  This tendon attaches the biceps muscle on the front of the arm to the radius allowing supination and flexion of the elbow.
• Triceps Tendon
  This tendon attaches the triceps muscle on the back of the arm to the ulna bone allowing the elbow to straighten, or extend.
• Lateral Epicondyle
  This bony prominence located just above the elbow on the outside is where the forearm muscles that extend the fingers and wrist come together in one tendon to attach to the humerus.
• Medial Epicondyle
  This bony prominence located just above the elbow on the inside is where the muscles that flex the fingers and wrist come together in one tendon to attach to the humerus.

Ligaments

Ligaments are strong rope like tissue that connects bones to other bones. Ligaments around the elbow join to form a watertight sac called a joint capsule. This capsule surrounds the elbow joint and contains lubricating fluid called synovial fluid.

There are four main ligaments in the elbow.

• Medial collateral ligament
  Located on the inside of the elbow, this ligament connects the humerus to the ulna.
• Lateral collateral ligament
  Located on the outside of the elbow, this ligament connects the humerus to the radius.
• The lateral ulnar collateral ligament
  Located on the outside of the elbow, this ligament connects the humerus to the ulna.
• Annular ligament
  This ligament forms a ring around the head of the radius, holding it tight against the ulna.

Muscles

Muscles are fibrous tissue capable of contracting to cause body movement.

• Biceps
  This is the large muscle on the front of the arm above the elbow that allows supination and flexion of the elbow.
• Triceps
  This is the large muscle on the back of the arm above the elbow enabling elbow extension, or straightening of the elbow.
• Brachialis
  This muscle is the primary elbow flexor enabling bending of the elbow. It is located at the distal end of the humerus.
• Wrist extensors
  These muscles of the forearm attach to the lateral epicondyle enabling extension of the fingers and wrist.
• Wrist flexors
  These muscles of the forearm attach to the medial epicondyle enabling flexion of the fingers and wrist.

Nerves

Nerves are responsible for carrying signals back and forth from the brain to muscles in our body, enabling movement and sensation such as touch, pain, and temperature.

The three main nerves of the arm are:

• Radial nerve
• Ulnar nerve
• Median nerve

Blood Vessels

The main blood vessel of the arm is the brachial artery. This artery travels across the elbow and then splits into two branches below the elbow.

These branches are:

Radial Artery: The radial artery is the largest artery supplying the hand and wrist area. Traveling across the front of the wrist, nearest the thumb, it is this artery that is palpated when a pulse is counted at the wrist.

Ulnar Artery: The ulnar artery travels next to the ulnar nerve through Guyon’s canal in the wrist. It supplies blood flow to the front of the hand, fingers and thumb.

Bursae

Bursae are small fluid filled sacs that decrease friction between tendons and bone or skin. Bursae contain special cells called synovial cells that secrete a lubricating fluid. When this fluid becomes inflamed or infected, a common painful condition known as Bursitis can develop.