Dr Ian Lo on Shoulder Pain

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Dr Ian Lo on Shoulder Pain

Ow! I just hurt my shoulder

 

How common is shoulder pain?

Probably most of us at some time or other have had shoulder pain or know someone who has had shoulder pain. The shoulder is one of the most complex joints in the body. Because of its inherent mobility and constant usage, the chance of developing shoulder pain is high. In fact, the lifetime risk of developing shoulder pain has been reported to be as high as 70%! This makes shoulder pain one of the most common disabling musculoskeletal complaints.

 

What is the shoulder anyways?

But the shoulder actually just isn’t one joint, it consists of 5 joints or articulations. The major joint is the glenohumeral joint (i.e. the ball and socket joint), which is formed by the humeral head (i.e. the proximal part of the humerus) and glenoid (i.e. part of the scapula or shoulder blade). This is what most people consider the shoulder joint. Other joints include the acromioclavicular joint which is formed by the lateral (i.e. outer) end of the clavicle (i.e. collar bone) and the acromion (i.e. part of the scapula) and the sternoclavicular joint formed by the medial (i.e. inner) end of the clavicle and the sternum (i.e. breast bone). Two other articulations are the subacromial space or bursa (i.e. the articulation between the rotator cuff and acromion) and the scapulothoracic joint or bursa (i.e. the articulation between the undersurface of the shoulder blade and the rib cage). These two articulations aren’t really joints but are just as important for the function of the shoulder joint.

 

How does the shoulder move?

To make things just a little more complicated, joints of course dont just move themselves. It is the muscles around the shoulder, which moves joints and around the shoulder there are a lot of muscles. These include all the individual muscles that move each of the bones about the shoulder. These include the muscles about the glenohumeral joint (e.g. the rotator cuff), the muscles about the shoulder blade (sometimes called the parascapular muscles e.g. trapezius, levator scapulae, serratus anterior), the muscles about the clavicle (e.g. sternocleidomastoid, subclavius), and the major muscles movers of the shoulder (e.g. deltoid, pectoralis major, latissimus dorsi).

 

As you might imagine, all these muscles have to work in a coordinated way moving each of the joints of the shoulder to allow smooth stable motion. That can be a complicated process! Luckily we’ve been practicing that our whole lives. But the shoulder is so delicately balanced that a problem in just one joint or muscle can lead to dysfunction of their entire shoulder resulting in pain, loss of motion and loss of function.

 

But what’s the most common cause of pain?

In the shoulder, pain can be from many sources. In fact shoulder pain can be referred from other regions of the body such as the neck or even the abdomen. But the most common causes of shoulder pain are from the muscles, tendons and joints that surround the shoulder.

In adults, the rotator cuff is the most common source of pain. Most of us have probably heard of the rotator cuff but it’s actually formed from four muscles that surround the shoulder and function as an integrated unit. These four muscles include the supraspinatus, infraspinatus, subscapularis and teres minor. Each of these muscles individually provides specific motions to the shoulder such as internal rotation (i.e. inward rotation of the shoulder) and external rotation (i.e. outward rotation of the shoulder). But also more importantly the rotator cuff functions as an integrated unit to provide dynamic stability to the glenohumeral joint.

 

In our next post we are going to go more in depth about the rotator cuff -how it functions, how it can get injured and how we can maintain its health.

References:

 

  1. Luime JJ, Koes BW, Hendriksen IJM, et al. Prevalence and incidence of shoulder pain in the general population: A systematic review. Scand J Rheumatol 2004, 33(2):73-81.
  2. The American Academy of Orthopaedic Surgeons. www.orthoinfo.aaos.org
  3. The American Orthopaedic Society for Sports Medicine. www.sportmed.org

 

Dr Ian Lo, RE-7 and its subsidiaries do not endorse any information, treatments, procedures, products, or physicians referenced herein. This information is provided as an educational service and is not intended to serve as medical advice. Anyone seeking specific medical advice or assistance should consult his or her physician.

 

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