The Elbow is a complex hinge joint formed by the articulation of three bones – lower portion of humerus (arm bone), upper ends of radius and ulna (forearm bones).

The humerus connects the shoulder to the elbow forming the upper portion of the hinge joint. The forearm consists of two bones, the radius (on the thumb side) and the ulna (on the little finger side). These bones connect the wrist to the elbow to form the lower portion of the hinge joint. A joint capsule surrounds the elbow joint which contains lubricating fluid called synovial fluid.

The three joints or articulations at the elbow are

Ulno-humeral joint: articulation between the upper ulna and lower humerus

Radio-humeral joint: articulation between the upper radius and lower humerus

Proximal radio-ulnar joint: articulation between the upper radius and upper ulna

The elbow is held in place with the support of various soft tissues including Cartilage, Tendons, Ligaments, Muscles, Nerves, Blood vessels and Bursae.

Ligaments are strong fibrous tissues that connect one bone to another.

Three ligaments are present in the elbow joint: the ulnar collateral ligament, the radial collateral ligament, and the annular ligament. These ligaments provide strength and support to the elbow joint along with the surrounding muscles of the arm and forearm while still allowing motion to occur.

If an injury occurs to the elbow joint, any one of these ligaments may be injured.

Annular Ligament: courses around the head of the radius bone. It keeps the radius in place when rotating the forearm inwards and outwards.

Ulnar Collateral Ligament (UCL): is a strong fan-shaped condensation of the fibrous joint capsule. It is located on the medial (inner) side of the joint and extends from the medial epicondyle of the humerus to the proximal (upper) portion of the ulna. The UCL protects the elbow against severe valgus stress or pressure from the outside of your arm.

Radial Collateral Ligament: is also a strong fan-shaped condensation of the fibrous joint capsule. It is located on the lateral (outer) side of the joint, extending from the lateral epicondyle of the humerus to the head of the radius. This ligament protects the joint against excessive varus, or inner to outer, stress.

The elbow is crossed over by two powerful tendons coursing from the arm into the forearm:

The biceps tendon passes in front of the elbow and gets attached to the bicipital tuberosity on the upper radius bone.

The triceps tendon passes at the back of the elbow and is attached to the olecranon process of the upper ulna. This tendon is covered with olecranon bursa, a fluid filled sac that assists friction free movements.

The various movements of an elbow joint are:

Flexion (bending of elbow)

Extension (straightening of elbow)

Pronation (forearm faces downwards or backwards)

Supination (forearm facing upwards or forwards)