ELBOW JOINT 195 



ARTICULATIONS. 



ARTICULATIO CUBITI (ELBOW JOINT). 



This joint includes (i) the articulatio humero-ulnaris, (2) 

 the articulatio humero-radialis, and (3) the articulatio radio- 

 ulnaris proximalis. In the humero-ulnar articulation the 

 trochlea of the humerus is grasped by the semilunar 

 notch of the ulna. In the radio-humeral articulation the 

 capitulum of the humerus rests in the shallow fovea capituli of 

 the radius, and in the proximal radio-ulnar articulation the 

 articular circumference of the head of the radius is held in 

 apposition with the radial notch of the ulna by the annular 

 ligament (Figs. 85, 96). 



The joint is surrounded by a capsule which is reinforced at 

 the sides by collateral ligaments ; in addition, the interosseous 

 membrane, which passes between the interosseous crests of the 

 radius and ulna, and the oblique cord, which connects the 

 tuberosity of the ulna with the proximal part of the inter- 

 osseous crest of the radius, help to keep the radius and ulna in 

 apposition, and are therefore included in the ligaments of the 

 elbow joint. The ligaments of the elbow joint are therefore 



1. Capsula articularis. 



2. Lig. collaterale ulnare. 



3. Lig. collaterale radiale. 



4. Lig. annulare radii. 



5. Membrana interossea antibrachii. 



6. Chorda obliqua. 



The articular capsule is attached proximally to the antero- 

 medial and antero-lateral surfaces of the humerus, proximal to 

 the coronoid and radial fossae, respectively. At the sides, 

 it is attached to the epicondyles ; and, posteriorly, to the 

 posterior surface, on which the line of attachment passes through 

 the proximal part of the olecranon fossa. Distally, the capsule 

 is attached to the anterior margin of the proximal, medial, 

 and lateral surfaces of the olecranon ; to the medial and volar 

 margins of the coronoid process of the ulna, and to the an- 

 nular ligament of the radius. The anterior part of the capsule 

 consists of fibres which take an irregular course over the 

 anterior aspect of the joint. The posterior part of the 

 capsule is weaker than the anterior and its attachment to 

 the posterior surface of the humerus is comparatively loose. 



The cavity of the joint is closed distally on the radial 

 side by lax fibres which pass from the distal border of the 

 annular ligament to the neck of the radius, and by a thin 

 sheet of fibres, called the ligamtntum quadratum, which extends 



i 13 a 



