Shoulder Region: Anatomy, Biomechanics, and Common Issues

Study Notes

Shoulder Region: Anatomy, Biomechanics, and Common Issues

The shoulder region is a complex area in the human body, consisting of multiple joints and muscles that work together to provide a wide range of motion. This article will discuss the anatomy, biomechanics, and common issues related to the shoulder region.

Anatomy

The shoulder joint, also known as the glenohumeral joint, is a ball and socket joint with a large range of motion. It is comprised of the glenoid fossa, which is the concave surface of the scapula, and the convex head of the humerus. Surrounding the joint are the glenohumeral ligaments, glenoid labrum, shoulder joint capsule, and the myotendinous attachments of the rotator cuff muscles. The rotator cuff muscles, including the supraspinatus, infraspinatus, teres minor, and subscapularis, play a crucial role in providing stability to the shoulder joint. Other muscles in the shoulder region include the pectoralis major, pectoralis minor, deltoids, trapezius, and serratus anterior.

Biomechanics

The shoulder complex includes three physiological joints and one floating joint: the glenohumeral (GH) joint, the acromioclavicular (AC) joint, the sternoclavicular (SC) joint, and the scapulothoracic (ST) joint. The GH joint is particularly important for understanding shoulder injuries, as it is a ball and socket synovial joint where the humeral head articulates with the glenoid fossa of the scapula. The joint heavily depends on the surrounding soft tissues for structural support, as only 25% of the humeral head articulates with the glenoid fossa at any one time during movements. The surrounding passive structures, such as the labrum, joint capsule, and ligaments, as well as the active structures, including the muscles and associated tendons, work cooperatively in a healthy shoulder.

Common Issues

One common issue in the shoulder region is subacromial bursitis, which occurs in the subacromial space between the coracoacromial arch and the head of the humerus. This condition can cause pain and inflammation, often due to repetitive overhead movements or repeated steroid injections that increase the risk of infection in the shoulder. Treatment typically involves avoiding activities that require overhead movements, taking oral NSAIDs, and rest.

Another issue is the presence of bursae in the shoulder region. There are eight bursae in the shoulder, more than any other joint in the body, which have a nerve supply and mechanoreceptors that aid in lubrication and movement. Inflammation of these bursae can lead to pain, decreased range of motion, loss of strength, and loss of functionality. Shoulder bursitis is often caused by overload, trauma, inflamed joints, or aging and can be difficult to differentiate from other shoulder pathologies. Treatment typically involves ultrasound-guided injections in combination with physical therapy, which can reduce pain and improve function.

In summary, the shoulder region is a complex area of the body with multiple joints and muscles that work together to provide a wide range of motion. Common issues, such as subacromial bursitis and shoulder bursitis, can cause pain, inflammation, and decreased functionality. Treatment typically involves a combination of rest, medication, physical therapy, and, in some cases, surgical intervention.

Description

Explore the anatomy, biomechanics, and common issues related to the complex shoulder region. Learn about the shoulder joint, rotator cuff muscles, and common shoulder problems like subacromial bursitis and shoulder bursitis.