322 SYNDESMOLOGY 



The Posterior Ligament (Fig. 330). This posterior ligament is thin and mem- 

 branous, and consists of transverse and oblique fibers. Above, it is attached to 

 the humerus immediately behind the capitulum and close to the medial margin 

 of the trochlea, to the margins of the olecranon fossa, and to the back of the lateral 

 epicondyle some little distance from the trochlea. Below, it is fixed to the upper 

 and lateral margins of the olecranon, to the posterior part of the annular ligament, 

 and to the ulna behind the radial notch. The transverse fibers form a strong band 

 which bridges across the olecranon fossa; under cover of this band a pouch of 

 sy no vial membrane and a pad of fat project into the upper part of the fossa when 

 the joint is extended. In the fat are a few scattered fibrous bundles, which pass 

 from the deep surface of the transverse band to the upper part of the fossa. This 

 ligament is in relation, behind, with the tendon of the Triceps brachii and the 

 Anconaeus. 



The Ulnar Collateral Ligament (ligamentum collaterale ulnare; internal lateral 

 ligament) (Fig. 329). This ligament is a thick triangular band consisting of two 

 portions, an anterior and posterior united by a thinner intermediate portion. The 

 anterior portion, directed obliquely forward, is attached, above, by its apex, to the 

 front part of the medial epicondyle of the humerus; and, below, by its broad base 

 to the medial margin of the coronoid process. The posterior portion, also of trian- 

 gular form, is attached, above, by its apex, to the lower and back part of the medial 

 epicondyle; below, to the medial margin of the olecranon. Between these two 

 bands a few intermediate fibers descend from the medial epicondyle to blend with 

 a transverse band which bridges across the notch between the olecranon and the 

 coronoid process. This ligament is in relation with the Triceps brachii and Flexor 

 carpi ulnaris and the ulnar nerve, and gives origin to part of the Flexor digitorum 

 sublimis. 



The Radial Collateral Ligament (ligamentum collaterale radiale; external lateral 

 ligament) (Fig. 330). This ligament is a short and narrow fibrous band, less dis- 

 tinct than the ulnar collateral, attached, above, to a depression below the lateral 

 epicondyle of the humerus; below, to the annular ligament, some of its most pos- 

 terior fibers passing over that ligament, to be inserted into the lateral margin of 

 the ulna. It is intimately blended with the tendon of origin of the Supinator. 



Synovial Membrane (Figs. 331, 332). The synovial membrane is very extensive. It extends 

 from the margin of the articular surface of the humerus, and lines the coronoid, radial and olec- 

 ranon fossae on that bone; it is reflected over the deep surface of the capsule and forms a pouch 

 between the radial notch, the deep surface of the annular ligament, and the circumference of the 

 head of the radius. Projecting between the radius and ulna into the cavity is a crescentic fold of 

 synovial membrane, suggesting the division of the joint into two; one the humeroradial, the 

 other the humeroulnar. 



Between the capsule and the synovial membrane are three masses of fat: the largest, over 

 the olecranon fossa, is pressed into the fossa by the Triceps brachii during the flexion ; the second, 

 over the coronoid fossa, and the third, over the radial fossa, are pressed by the Brachialis into 

 their respective fossae during extension. 



The muscles in relation with the joint are, in front, the Brachialis; behind, the Triceps brachii 

 and Anconseus; laterally, the Supinator, and the common tendon of origin of the Extensor muscles; 

 medially, the common tendon of origin of the Flexor muscles, and the Flexor carpi ulnaris. 



The arteries supplying the joint are derived from the anastomosis between the profunda and 

 the superior and inferior ulnar collateral branches of the brachial, with the anterior, posterior, 

 and interosseous recurrent branches of the ulnar, and the recurrent branch of the radial. These 

 vessels form a complete anastomotic network around the joint. 



The nerves of the joint are a twig from the ulnar, as it passes between the medial condyle and 

 the olecranon; a filament from the musculocutaneous, and two from the median. 



Movements. The elbow-joint comprises three different portions viz., the joint between 

 the ulna and humerus, that between the head of the radius and the humerus, and the proximal 

 radioulnar articulation, described below. All these articular surfaces are enveloped by a common 

 synovial membrane, and the movements of the whole joint should be studied together. The com- 

 bination of the movements of flexion and extension of the forearm with those of pronation and 

 supination of the hand, which is ensured by the two being performed at the same joint, is essential 

 to the accuracy of the various minute movements of the hand. 





