THE ELBOW-JOINT. 



325 



(Figs. 305 and 306) is a fan-shaped structure of unequal thickness, but its margins, 

 which are its strongest bands, are continuous with the adjoining parts of the 

 anterior and posterior ligaments. By its proximal end it is attached to the 

 anterior, distal, and posterior aspects of the medial epicondyle of the humerus. By 

 its broad distal end it is attached to the medial margin of the semilunar notch, so 

 that the anterior land is associated principally with the medial margin of the 

 coronoid process, and the posterior land with the medial margin of the olecranon, 

 while the intermediate weaker portion sends its fibres downwards to join a trans- 

 verse land, sometimes very strong, which bridges the notch between the adjoining 

 medial margins of the coronoid process and the olecranon. 



Lig. Collaterale Radiale. The radial collateral ligament (O.T. external 

 lateral) (Fig. 305) is a strong flattened band attached proximally to the distal and 



Interosseous membrane Radius 



Medial epicondyle 



Anterior part of ulnar 

 collateral ligament 



Posterior part of ulnar 

 collateral ligament 



Olecranon 



Ulna Transverse part of ulnar collateral ligament 



FIG. 306. ELBOW- JOINT (Medial Aspect). 



posterior aspects of the lateral epicondyle of the humerus. It completes the con- 

 tinuity of the articular capsule on the lateral side, and blends distally with the 

 lig. annulare radii, on the surface of which its fibres may be traced both to the 

 anterior and posterior ends of the radial notch of the ulna. Both of the collateral 

 ligaments are intimately associated with the muscles which take origin from the 

 medial and lateral epicondyles of the humerus. 



Synovial Pads of Fat (Fig. 307). Internal to the fibrous stratum of the 

 articular capsule, there are several pads of fat situated between it and the syiiovial 

 stratum. Small pads are so placed as to lie immediately in front of the coronoid 

 and radial fossse, but a larger one projects towards the olecranon fossa. 



A stratum synoviale (Fig. 307) lines the entire fibrous stratum and clothes 

 the pads of fat referred to above, as well as those portions of bone enclosed within 

 the capsule which are not covered by articular cartilage. By its disposition the 

 elbow and the proximal radio-ulnar joints possess a common joint cavity. It 

 should be specially noted that the proximal part of the neck of the radius is 

 surrounded by this synovial layer. 



Movements at the Elbow-Joint. The movements of the radius and ulna upon the humerus 

 have already been referred to as those characterising a uniaxial joint constructed on the plan of 

 a hinge. In this case the axis of the joint is obliquely transverse, so that in the extended 

 position the humerus and ulna form an obtuse angle open towards the radius, whereas in the 



