Last revised by Craig Hacking on 27 Mar 2024

The elbow is a complex synovial joint formed by the articulations of the humerus, the radius, and the ulna

The elbow joint is made up of three articulations 2,3:

  • radiohumeral: capitellum of the humerus with the radial head

  • ulnohumeral: trochlea of the humerus with the trochlear notch (with separate olecranon and coronoid process articular facets) of the ulna

  • radioulnar: radial head with the radial notch of the ulna (proximal radioulnar joint)

In full flexion, the coronoid process is received by the coronoid fossa and the radial head is received by the radial fossa on the anterior surface of the humerus. In full extension, the olecranon process is received by the olecranon fossa on the posterior aspect of the humerus 1.

The elbow is a trochoginglymoid (combination hinge and pivot) joint 4, 5:

  • medial (ulnar) collateral ligament complex

  • lateral (radial) collateral ligament complex

  • oblique cord

    • inconstant thickening of supinator muscle fascia and functionally insignificant 5

    • runs from tuberosity of the ulna to just distal to radial tuberosity 5

  • quadrate ligament (of Denuce)

    • thickening of the inferior aspect of the joint capsule

    • runs from just inferior to the radial notch of the ulna to insert to the medial surface of the radial neck 11

The joint capsule has two layers, deep and superficial, and attaches proximally to the radial, coronoid and olecranon fossae. Distally, it attaches to the annular ligament of the radius and coronoid process of the ulna 1,3,5. The volume of the joint capsule is 24-30 mL 9. There are several synovial folds of the elbow.

There are three fat pads of the elbow, which sit between the two layers of the joint capsule, making them extrasynovial 3,4:

  • coronoid fossa fat pad (anterior)

  • radial fossa fat pad (anterior)

  • olecranon fossa fat pad (posterior)

Displacement of fat pads is a radiographic feature of an elbow joint effusion.

  • superficial olecranon bursa: lies between the olecranon and the subcutaneous tissue 4,5

  • subtendinous olecranon bursa: lies between olecranon and triceps brachii tendon 8

  • intratendinous olecranon bursa: variably lies in the triceps brachii tendon 8

  • bicipitoradial bursa

Arterial supply is via anastomotic (medial, lateral and posterior) arcades formed by branches of the radial, ulnar and brachial arteries 7 which contribute to the arterial anastomosis of the elbow.

Multiple articular branches are derived from several nerves (Hilton's law) 1:

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