The shoulder complex design enables great mobility of the upper extremity. As a result, the hand can be placed almost anywhere within a sphere of movement, its range limited primarily by the length of the arm and the space taken up by the body. The combined mechanics of the three synovial and two functional joints with the many muscles that comprise the shoulder complex interact to provide and control the mobility. When establishing a therapeutic exercise program for impaired function of the shoulder region, as with any other body region, the unique anatomical and kinesiological features must be considered along with the state of pathology and functional limitations imposed by the impairments.
This chapter is divided into three main sections. The first section reviews the structure and function of the shoulder complex. The second section describes common shoulder disorders and provides guidelines for conservative and postsurgical management. The last section describes exercise techniques commonly used to meet the goals of treatment during the stages of tissue healing and phases of rehabilitation.
Structure and Function of the Shoulder Girdle
The shoulder girdle has only one bony articulation with the axial skeleton (Fig. 17.1). The clavicle articulates with the sternum via the small sternoclavicular (SC) joint, and this reduced articular contact area is an important reason for the considerable mobility of the upper extremity. Stability, however, is hampered by this articular arrangement and relies on an intricate balance among the scapular and glenohumeral (GH) muscles and the soft tissue structures of the joints in the shoulder complex.
Bones and joints of the shoulder girdle complex.
Joints of the Shoulder Complex
Three synovial joints (GH, acromioclavicular [AC], and SC) and two functional articulations (scapulothoracic and suprahumeral) make up the shoulder complex.
The GH joint is an incongruous, ball-and-socket (spheroidal) triaxial joint with a lax joint capsule. It is supported by the tendons of the rotator cuff and the GH (superior, middle, inferior) and coracohumeral ligaments (Fig. 17.2). The concave joint surface, the glenoid fossa, is located on the superior-lateral margin of the scapula. It faces primarily laterally, somewhat anteriorly, and slightly upward, providing minimal stability to the joint. A fibrocartilagenous lip, the glenoid labrum, deepens the fossa to increase joint congruity and stability and serves as the attachment site for the capsule. The convex joint surface is the hemispheric head of the humerus. Only a small portion of the head contacts the fossa at any time, allowing for considerable joint movement but also the potential for instability.155
Ligaments of the glenohumeral (GH) and acromioclavicular (AC) joints.