Figure 13.1 Articulations forming the elbow joint. (A) Anterior view. (B) Lateral view.

The contact area between the joint surfaces of the elbow complex increases throughout flexion. In full extension the lower medial part of the trochlear notch of the ulna is used, with no contact occurring between the radius and ulna. At 90 degrees the contact area is a diagonal (lower medial to upper lateral) across the trochlear surface, with only slight pressure between the humerus and radial head. In full flexion definite contact occurs between the radius and ulna, and the trochlear contact areas increase (Fig. 13.3). Full flexion is thus required to ensure adequate nutrition of the whole articular cartilage, a situation sometimes not possible in obese or heavily muscled individuals due to the approximation of the flexor soft tissues.