The elbow joint is formed between the distal articulating surface of the humerus and the proximal articulating surfaces of the radius and ulna. The joint allows for flexion and extension and is moved by powerful muscles both in front and behind the joint.
The elbow is a simple fulcrum (hinge) joint. The action of flexion and extension occur at the humeroulnar joint, with the trochlea of the humerus articulating with the sling like trochlea notch of the humerus. Powerful muscles that lie in front of the joint will cause elbow flexion i.e. brachialis and biceps brachii. The muscle behind the joint will cause extension (triceps brachii).
The trochlea of the humerus articulates with the trochlear notch of the ulna and provides congruence and stability. The coronoid fossa of the humerus receives the tip of the coronoid process, and helps prevent posterior dislocation. The elbow has both static and dynamic stabilisers. The static stabilisers include the humeroulnar joint, with the coronoid process of the ulna fitting into the coronoid fossa of the humerus. The joint capsule and medial and lateral collateral ligements. The medial collateral ligament has anterior, posterior and transverse bundles. The ligament protects the joint from valgus stress, and the anterior bundle of the medial collateral ligament will insert onto the sublime tubercle (a bony landmark on the ulna). The lateral collateral ligament protects against varus stresses, and consists of the radial collateral ligament, the annular ligament and the lateral ulnar collateral ligament. Dynamic stabilisers are the several muscles that cross the joint i.e. brachialis, anconeus, triceps brachii.
The capitulum of the humerus articulates with the radius bone of the forearm. The head of the radius sits within the annular ligament, which is attached to the radial notch of the ulna, this is and intra-articular structure. The limit to elbow extension occurs because of the prominent olecranon process articulating within the olecranon fossa of the humerus. The humeroradial joint is more supportive, with the two bones articulating but not in a high degree of congruence. The proximal radioulnar joint is located just inferior to this joint. The musculocutaneous, median, ulnar and radial nerves innervate the elbow joint. Blood supply to the elbow is from the brachial artery via the Supratrochlear, nutrient and superior and inferior ulnar collaterals.
There are a large number of bursae around the elbow joint, but only three that have clinical relevance. The intratendinous bursa is formed between the tendons of triceps brachii. The subcutaneous bursa is formed between the olecranon and the overlying tendinous tissue and skin. The subtendinous can be found between the olecranon and the overlying tendon of triceps brachii. Friction is therefore reduced during elbow flexion and extension.
Developmental precursor- Limb bud, somatic layer of lateral mesoderm
Blood supply- Supratrochlear, nutrient and ulnar collateral arteries
Nerve supply- median, ulnar, musculocutaneous and radial nerves.Bursae- Subcutaneous, subtendinous, intratendinous