The shoulder complex, as it sounds, is a very complex area of the body. It is comprised of the clavicle (collar bone), sternum, scapula (shoulder blade) and humerus. The articulations of all of these bones allows for the 360° of mobility at the “shoulder joint”. There are four major articulations associated with the shoulder complex:
1. Sternocalvicular Joint –the articulation where the manubrium of the sternum meets the clavicle. The area is the only direct connection between the upper extremity and trunk. The anterior and posterior Sternoclavicular ligaments connects the two bones strengthening the anterior and posterior joint respectively. There is a fibrocartilage disc which functions as a shock absorber. The disc is positions so that the clavicle may move up and down, forward and backward, in combination and in rotation.
2. Acromioclavicular Joint – the articulation between the lateral end of the clavicles with the acromion process of the scapula. It is a fairly week joint by a fibrocartilage disc and encased in a thin fibrous capsule. Both the acromioclavicular ligament and the coracoclavicular ligament prevent upward displacement of the clavicle.
3. Glenohumeral Joint – This is the ball-and-socket joint typically called the “shoulder joint”. The round head of the humerus (the ball) and the glenoid cavity of the scapula (the socket) make up this joint. The coracohumeral ligment connects from the coracoid process of the scapula to the humerus strengthening the superior part of the joint. The glenohumeral ligament connects from the apex of the glenoid cavity of the scapula to the humerus strengthening the anterior part of the joint. The glenoid labrum is a band of fibrocartilage that attaches within the glenoid cavity helping to deepen the cavity.
4. Scapulothoracic Joint – This is not actually a true joint, better described as the movement of the scapula along the thoracic cage. However, this movement is critical to shoulder motion. The muscles that attach from the rib cage and spine stabilize the scapula providing the base from which the shoulder joint can function. The scapulothoracic joint allow for elevation, depression, protraction, retraction, abduction and adduction of the scapula.
The high mobility of the shoulder joint leads to less stability. For dancers, the common types of injuries to the shoulder joint and complex include dislocations, tendinitis of tendon of the bicep, bursitis, and muscular tears in the rotator cuff. These injuries often occur when there is lifting involved. To help prevent these issues conditioning of the muscles supporting the movement of the joint should be strengthened as well as ensuring lifting is done safely and efficiently.
Here are six basic principles(1) that can be used for efficient lifting:
Key muscle groups to strengthen for lifting:
1. Fitt, S. S. (1996). Muscles of the Scapula and the Shoulder. In Dance Kinesiology (2nd ed., pp. 193–208). Schirmer Books.
2. Prentice, W. E. (2009). Anatomy of the Shoulder. In Arnheim’s Principles of Athletic Training: a competency-based approach (13th ed., pp. 743–749). New York: McGraw-Hill Higher Education.
photo credit: http://www.whitetigernaturalmedicine.com/craniosacral-therapy/craniosacral-therapy-upper-shoulder-pain
CarliAnn & Ella