Articular capsule of elbow joint

At a glance

English

Articular capsule of elbow joint

Latin (TA2)

Capsula articularis articulation cubiti

System

Joint

Region

Upper limb

Side

Paired, left and right

About the articular capsule of elbow joint

The articular capsule of the elbow joint is one continuous envelope that encloses three articulations: the humeroulnar and humeroradial parts of the elbow and the proximal radioulnar joint. Above, it attaches to the front of the humerus just above the coronoid and radial fossae and to the back just above the olecranon fossa, leaving the epicondyles outside. Below, it is fixed to the edges of the coronoid process and olecranon of the ulna and to the annular ligament that encircles the head of the radius. The radius itself has no direct capsular attachment, so the head is free to turn inside the ring.

At the sides the capsule is reinforced by two triangular collateral ligaments, while front and back it is thin and relatively weak, suiting a hinge that moves only in one plane. The anterior wall is made mostly of longitudinal fibres, with oblique and transverse bundles adding strength. Deep fibres of brachialis insert into it and draw it upwards in flexion so it is not trapped. The posterior wall is thinner and largely transverse; some fibres bridge the olecranon fossa as a band with a free upper edge, and the triceps tendon pulls the capsule clear during extension.

Inside, the synovial membrane is extensive. It lines the three fossae of the humerus, reaches the radial neck below the annular ligament, where the quadrate ligament supports it, and forms several folds. Fat pads lie between the membrane and the fibrous capsule over the fossae. The ulnar collateral ligament fans out from the medial epicondyle, reaching the coronoid process and olecranon; the radial collateral ligament runs from the lateral epicondyle into the annular ligament.

On a lateral X-ray, fluid in the joint lifts these fat pads, and a visible posterior fat pad suggests a hidden fracture. Forced hyperextension can tear the anterior capsule, and stiffness after injury often stems from capsular contracture.

Attachments and function

Formed by

Attached to the humerus above the coronoid and radial fossae in front and above the olecranon fossa behind, sparing the epicondyles.

Joins

Attached to the margins of the coronoid process and olecranon of the ulna, and to the annular ligament round the radial head.

Movements

Encloses the elbow and proximal radioulnar joints, allowing flexion and extension, and with its collateral ligaments resists side-to-side movement.

Nerve supply

Branches of the musculocutaneous, median and radial nerves in front, and of the ulnar nerve and the radial branch to anconeus behind.

Blood supply

The anastomosis round the elbow, from the collateral branches of the brachial and deep brachial arteries and the recurrent branches of the radial, ulnar and interosseous arteries.