02/08/2020
🔈 THE FIVE JOINTS OF THE SHOULDER
Right shoulder, anterior view. A total of five joints contribute to the wide range of arm motions at the shoulder joint. There are three true shoulder joints and two functional articulations:
✅ True joints:
1. Sternoclavicular joint
2. Acromioclavicular joint
3. Glenohumeral joint
✅ Functional articulations:
4. Subacromial space: a space lined with bursae (subacromial and subdeltoid bursae) that allows gliding between the acromion and the rotator cuff (muscular cuff of the glenohumeral joint, consisting of the supraspinatus, infraspinatus, subscapularis, and teres minor muscles, which press the head of the humerus into the glenoid cavity.
5. Scapulothoracic joint: loose connective tissue between the subscapularis and serratus anterior muscles that allows gliding of the scapula on the chest wall.
Besides the true joints and functional articulations, the two ligamentous attachments between the clavicle and first rib (costoclavicular ligament) and between the clavicle and coracoid process (coracoclavicular ligament) contribute to the mobility of the upper limb. All of these structures together comprise a functional unit, and free mobility in all the joints is necessary to achieve a full range of motion.
This expansive mobility is gained at the cost of stability, however. Since the shoulder has a loose capsule and weak reinforcing ligaments, it must rely on the stabilizing effect of the rotator cuff tendons. As the upper limb changed in mammalian evolution from an organ of support to one of manipulation, the soft tissues and their pathology assumed increasing importance. As a result, a large percentage of shoulder disorders involve the soft tissues.
Would you like to find out more about human anatomy, physiology and pathology? Stay tuned and make sure you turned on notification on Healthy Street and see all posts and updates.