A freely mobile but strong and stable elbow complex is required for normal upper extremity function. The design of the elbow and forearm adds to the mobility of the hand in space by shortening and lengthening the upper extremity and by rotating the forearm. The muscles provide control and stability to the region as the hand is used for various activities, from eating, dressing, and grooming to pushing, pulling, turning, lifting, throwing, catching, and reaching for objects to coordinated use of equipment, tools, and machines.39,50,65,68 Most activities of daily living require a 100° arc of flexion and extension at the elbow, specifically between 30° and 130° as well as 100° of forearm rotation, equally divided between pronation and supination.65 Tasks, such as drinking and eating, primarily require elbow flexion, whereas a task, such as reaching to tie shoelaces, requires substantial elbow extension.
Injury or disease of boney, articular, or soft tissue structures of the elbow and forearm can cause pain and compromised mobility, strength, stability, and functional use of the upper extremity. Loss of active or passive elbow flexion interferes with grooming and eating, whereas loss of elbow extension restricts a person's ability to push up from a chair or reach out for objects. In general, loss of terminal flexion of the elbow contributes to greater limitation of function than loss of terminal extension.65
The anatomical and kinesiological relationships of the elbow and forearm are outlined in the first section of this chapter. Chapter 10 presents information on principles of soft tissue healing and management; the reader should be familiar with that material before establishing a therapeutic exercise program to improve function of the elbow and forearm.
Structure and Function of the Elbow and Forearm
The distal end of the humerus has two articular surfaces: the trochlea, which articulates with the ulna, and the capitulum, which articulates with the head of the radius (Fig. 18.1). Flexion and extension occur between these two joint surfaces. The radius also articulates with the radial notch on the ulna and is called the proximal radioulnar joint. This joint participates in pronation and supination along with the distal radioulnar joint. The capsule of the elbow encloses the humeroulnar, humeroradial, and proximal radioulnar articulations. The distal radioulnar joint is structurally separate from the elbow complex even though its function is directly related to the proximal radioulnar joint.
Bones and joints of the elbow and forearm.
Joints of the Elbow and Forearm
There are four joints involved in elbow and forearm function: the humeroulnar, humeroradial, proximal radioulnar, and distal radial ulnar joints.
Elbow Joint Characteristics and Arthrokinematics