What Causes Shoulder Pain?

What Causes Shoulder Pain

I have had a few clients with shoulder pain of late so I decided to sit down and write a little about shoulder pain.

I wanted to put something together that I could print out and give to them so I could educate them on their shoulder pain.

This is the first part of the shoulder pain series – What causes shoulder pain?.


How Big of a Problem is Shoulder Pain?

Musculoskeletal disorders are the second leading reason for physician visits each year with about 132 million physician visits occurring in 2006 (American Academy of Orthopaedic Surgeons, 2009).

It is estimated that musculoskeletal disorders cost the United States almost $850 billion annually, and about 440 million work days are missed due to these health conditions.

With about 7.5 million physician visits each year, shoulder pain is a major contributor to the increasing disability caused by musculoskeletal disorders in developing nations (AAOS, 2009).

I always like to start off with some numbers.  The numbers are impressive.  It shows how big of an issue injuries are, especially shoulder pain.

4 Key Parts to the Shoulder

The shoulder girdle is composed of 3 bones and 3 main joints held together by ligaments (structures that connect bones to other bones), tendons (structures that connect muscles to bones), bursae and muscles.

Bone of the Shoulder Joint

The shoulder consists of these three bones:

  • humerus (upper arm bone)
  • scapula (shoulder blade)
  • clavicle (collar bone)

Joints of the Shoulder

Acromioclavicular Joint – A key structure on the the outer end of the scapula, protruding away from midline of the body is the acromion.  The acromion forms the highest point of the shoulder.  It is a key area for ligaments to attach and forms half of the acromioclavicular joint with the clavicle.

Glenohumeral Joint – The head or ball of the humerus fits into the shallow socket on the scapula, called the glenoid fossa, to form the glenohumeral joint.  This is the main joint of the shoulder and the joint that allows the high level of movement the shoulder has.

The head of the humerus is larger in comparison to the glenoid, and only one-third of the humeral head is in contact with the glenoid fossa.  A larger humeral head in contact with a shallow socket enables great movement in the joint but decreases the stability of the shoulder and leads to its increased risk of shoulder injuries.

The glenoid fossa is made deeper by a ring of fibrous cartilage surrounding the glenoid, called the labrum.  Extending and making the fossa deeper enhances stability of the shoulder joint.

Sternoclavicual Joint – The inner end of the clavicle connects to the sternum (breastbone), forming the sternoclavicular joint.  This joint is the only link of the shoulder and arms to the rest of the skeleton of the body.

Scapulathoracic joint – Is where the scapula moves up and down against the rib cage. This joint is not an actual joint as it depends entirely on the surrounding muscles during shoulder movements.

This shows that the shoulder is a very complex structure.  One specific shoulder joint may be injured but it will affect all of the other shoulder joints.

Muscles of the Shoulder

Rotator Cuff Muscles – A key set of muscles that stabilizes the shoulder joint are the rotator cuff muscles which have a key function of keeping the humeral head centered within the glenoid fossa. The tendons of supraspinatus, infraspinatus, teres minor and subscapularis muscles form the rotator cuff.  Injuries involving the rotator cuff and their tendons are one of the leading causes of shoulder pain.

Scapular Stabilizers – The set of muscles that connect to the scapula and assist in stabilizing and moving the scapula.

Shoulder Muscles – These are the large superficial muscles that you see when you look at the shoulder joint.  Examples of these muscles are the deltoid and latissimus dorsi.

Bursae of the Shoulder

Bursae are fluid-filled sacs that allow smooth gliding between two surfaces that move against one another.  There are many bursae associated with the shoulder joint.

Inflammation of the bursa located between the acromion and joint capsule that surround the glenohumeral joint and the bursa between the subscapularis and the joint capsule are the most common areas in the shoulder that can lead to shoulder bursitis and shoulder pain.

6 of the Most Common Shoulder Injuries

Any injury or disease affecting the supportive structures of the shoulder, such as the bones, tendons, bursae, cartilage, and ligaments can result in shoulder pain.

In general, wear and tear, overuse or repetitive overhead movements and trauma play a major role in the development of shoulder pain. The following are the common causes of shoulder pain:

#1 – Rotator Cuff Tendonitis

Tendonitis is the inflammation the rotator cuff tendon resulting from overuse or repetitive movements affecting the rotator cuff.

#2 – Rotator Cuff Tear

Overuse, repetitive overhead motions, aging or falling my result in degeneration of the rotator cuff tendon, which can cause incomplete or complete tearing of the rotator cuff.

Rotator cuff tears usually cause pain in the deltoid muscle, especially when the affected arm is lifted from the sides.

#3 – Shoulder Instability

Shoulder instability occurs when the humeral head is not sufficiently maintained within the center of the glenoid fossa.

If the joint becomes too loose, the head of the humerus may slide partially out of place, termed shoulder subluxation, or it may completely come out of place, a condition called a shoulder dislocation.

#4 – Frozen shoulder or Adhesive Capsulitis

Frozen shoulder is a tightening of the capsule that surrounds the shoulder joint which leads to poor movement of the shoulder and shoulder pain.

#5 – Shoulder Impingement

Shoulder impingement (squeezing of the rotator cuff tendon), most frequently occurs in the supraspinatus, underneath the bony arch of the acromion.

#6 – Arthritis of the Shoulder

Arthritis is a degenerative disease that usually occurs due to wearing and tearing of the affected joint, as in osteoarthritis, or due to a systemic inflammation, as in rheumatoid arthritis. Arthritis results in loss of protective cartilage in the shoulder joint which can cause pain and limited shoulder movement.

Other causes of shoulder pain include shoulder fractures, labral tears, calcific tendonitis, superior labrum from anterior to posterior or SLAP tears and biceps tendon ruptures.

Common Causes of Shoulder Pain

Increased Risk with Age – Shoulder pain is more common in individuals older than 40 years and is often the result of wear and tear on the shoulder.

Previous Shoulder Injury – In younger adults, shoulder pain is commonly associated with a previous injury.

Related to Sports Played or Work Performed – In addition, about 21% of shoulder pain associated with injuries was related to work (Wofford, Mansfield & Watkins, 2005).

Athletes and workers who execute repetitive overhead or throwing motions have greater risk for shoulder injuries and pain.  Examples of sports where athletes have greater risk of shoulder pain are swimming, tennis, baseball, volleyball and javelin.  Examples of occupations that are at greater risk of shoulder pain are carpenters, painters, construction workers and workers performed repeated overhead movements.

Posture – Bad postures and body mechanics also increase the risk of shoulder pain.  For example, forward rolled shoulders increases the risk for impingement syndrome. This type of posture can reduce the space to which the rotator cuff tendons or muscles goes through, which increase the risk of squeezing the structures underneath the acromion.

Diagnosis of Shoulder Pain

The cause of shoulder pain is mainly determined by medical history, results from a physical examination and findings on the diagnostic imaging tools.

If the pain is severe or if the cause is still undetermined through physical examination, your physician may recommend diagnostic imaging tests to obtain the accurate cause of the pain.  X-rays, a magnetic resonance imaging or an ultrasound may be ordered in order to provide better clarification of the injury and the severity of the injury.


I hope you enjoyed part one on Shoulder Pain and have a better idea of the magnitude of shoulder pain, the make up of the shoulder, common causes of shoulder pain and ways of diagnosing shoulder pain.

Rick Kaselj, MS

P.S. – If you are looking for other resources when it comes to shoulder pain, injuries and recovery, these may help:

Other articles on shoulder pain, injuries and recovery:

Fitness Education Courses on shoulder pain, injuries and recovery:

Books and products related to shoulder pain, injuries and recovery:



That is it for now!