The shoulder is a ball-and-socket joint. The shoulder is the most mobile and flexible joint in the human body as the ball is quite large compared to the shallow socket. The joint is reasonably stable due to the complex, delicately balanced arrangement of bones, muscles, tendons, and ligaments. Three bones are interconnected at the shoulder to form a girdle – collar bone (clavicle), shoulder blade (scapula), and humerus (bone in the arm – shoulder to elbow). Acromion is a part of the shoulder blade bone that projects above the humerus head and restricts upward arm movement at the shoulder joint. The ligaments of the shoulder joint are not very tight, and the capsule, too, is relatively lax, allowing free movement. Four small muscles (the rotator cuff) retain the head of the humerus in the socket and act as dynamic ligaments. Long muscles such as the deltoid (overlying shoulder), biceps (front of arm), triceps (back of arm), and others move the shoulder in various directions. The subacromial bursa, a fluid-filled sac, extends downwards under the acromion and acts as a cushion preventing the rubbing of rotator cuff tendons over the bones.
An extensive range of movement at the shoulder makes it more prone to injury and resultant pain. Pain interferes with day-to-day functions. In addition, it disturbs sleep as lying on the side of the affected shoulder is painful. The risk of shoulder problems is especially high in athletes, older people, and those who work with overhead movements (swimming, throwing, painting, and construction work).
Common problems around the shoulder joint leading to pain are as follows
- Frozen shoulder (Adhesive capsulitis): Mild to severe restriction of shoulder movement along with pain is a common complaint. Risk of frozen shoulder increases as age advances beyond 40 years. It is more common in females and those with diabetes, previous shoulder injury or surgery, heart or lung disease, stroke, and overactive thyroid gland. Deficiencies of calcium and vitamins B12 and D are also implicated in various conditions leading to shoulder weakness and pain. Inflammation of soft tissue around the shoulder joint leads to thickening and tightening due to adhesions and restricts joint movement. Frozen shoulder usually starts as pain for 3-9 months. This painful phase is followed by a phase of restricted motion lasting for 4-12 months. Discomfort and stiffness make it difficult to carry out routine activities such as making hair, buttoning a blouse, or reaching a high shelf. Pain in these activities is noted at the extreme of a particular motion. Lying on the affected side is also difficult due to the painful shoulder. The pain usually reduces slowly over 6-24 months. However, restriction persists, and the shoulder never regains its complete normal range of movement. Exercise under expert physiotherapy guidance is the best treatment for frozen shoulder. Painkillers can be used in the initial stages. In some cases, oral steroids may also be helpful in the early stages of frozen shoulder. A local steroid injection may reduce pain in some cases. Manipulation under general anesthesia and other surgical procedures should be considered in recalcitrant cases.
- Rotator Cuff Lesions (Swimmer's shoulder): Four rotator cuff muscles steady the shoulder during movements of the arm. Muscles of the rotator cuff or their tendons can get swollen due to repetitive overuse or torn during a single stressful event. Supraspinatus muscle and tendon, which form the upper part of the cuff, are often injured as they lie between bones. Pain and limitation of movements is a common feature. Pain is usually worse during overhead activities. Lifting the arm away from the body becomes painful. Avoidance of stressful shoulder movements (but not complete rest), painkillers, and exercises under the supervision of a physiotherapist is the treatment of choice. Local steroid injection or surgery may be required in selected cases.
- Calcific Tendonitis: The deposition of calcium (chalk-like)in rotator cuff tendons without any symptoms is seen in 3-20% population. It is more common in elderly individuals, although the process is not precisely age-related degeneration. The exact cause of calcium deposition is not known. Pain in calcific tendonitis can be of sudden onset and very severe. The pain may awaken a patient from sleep. The pain usually radiates lower down the arm and may radiate upwards towards the neck. Pain is often aggravated by raising the arm above the shoulder. Stiffness and weakness of the shoulder may be associated. Acute severe symptoms can resolve spontaneously in 3-4 weeks. In other non-acute cases, pain is mild with intermittent flares. The shoulder may get locked due to a large calcium deposit. X-ray of the shoulder may show calcification. 70% of patients respond to pain killers and exercises under the supervision of an expert physiotherapist. Local steroid injections, needling with lavage, and surgery may be contemplated in nonresponsive cases. Calcium depositions can recur in 16-18% of patients following surgery.
- Subarachnoid Bursitis: The Supraspinatus muscle originates from the top of the shoulder blade and runs under the acromion to get attached to the top of the humerus bone. A bursa, the largest in our body, intervenes between this muscle and acromion and protects friction of the muscle against bone. Inflammation of this Subacromial bursa usually results from overuse and may indicate degenerative joint disease. Painful movements and tenderness on pressure above the head of the femur bone are important features. In addition, swelling may present in the area. Treatment consists of painkillers, rest (avoidance of strenuous activities), exercises, and local steroid injections.
- Bicipital Tendinitis: One of the tendinous origins of the biceps muscle lies just in front of the shoulder joint. Bicipital tendinitis can occur as a part of rotator cuff lesions or may occur after unusual stress. Overuse and wear and tear are common causes of Bicipital tendinitis. The pain increases on local pressure below the front of the shoulder joint. Conservative treatment with painkillers, rest, and heat are usually sufficient. Local steroid injection also helps but must be given carefully as this can lead to rupture of the tendon. Surgery is rarely indicated.