The elbow joint consists of 3 joints:

  1.  Humeroulnar joint: the proximal ulna consists of the olecranon (posterior side) and the coronoid process (anterior side) and articulates with the humerus through the trochlea.  Its primary function is flexion and extension of the elbow.  
  2. Radiohumeral joint: the radial head articulates with the humerus though the capitellum.  Its primary function is pronation and supination of the lower arm.
  3. Proximal radioulnar joint: articulation between the radial head and the radial notch of the ulna. Its primary movement is rotation of the radial head. 

To open class X-elbow, just click on the right side of the screen on X-elbow under the section Techniques.