Although most shoulder problems are relatively short-lived, discomfort or pain from shoulder problems can indicate a more complex issue. To understand shoulder pain, we begin with a review of how the shoulder works and functions in the human body.

What is the shoulder?

The shoulder is a ball-and-socket joint1,2 made by the connection of the humerus, or the arm bone, in a shallow socket known as the glenoid fossa. The glenoid fossa is part of another bone called the scapula, more commonly known as the shoulder blade. In the front of the shoulder lies the clavicle, also known as the collar bone. On one end of the collarbone is the marriage of the clavicle with another part of the scapula called the acromion. This joint is called the acromioclavicular joint.  On the other end of the clavicle is the sternum, commonly known as the breastbone, which forms another joint: the sternoclavicular joint.

Around the shoulder bones is a complex arrangement of muscles, tendons, and the glenohumeral shoulder joint2 itself, lending to the versatility of the shoulder to engage in elevation, rotation, scaption, and other ranges of motion3. This interplay of muscle, bone and joint makes the shoulder the most mobile joint in the entire human body, allowing us to catch basketballs, brush our teeth, and reach overhead for groceries on the top shelf!

How do shoulder muscles work?

The flexibility of the shoulder joint is also what makes it prone to instability and injury. Muscles help provide much-needed support2,3 to the shoulder:

• Trapezius is a thick muscle that extends down the spine and across the back of the neck and shoulders into the arm.

• Serratus anterior spans the first eight ribs and helps elevate the scapula, such as throwing a punch.

• Deltoid is a large, triangular muscle spanning the glenohumeral joint and is shaped like a shoulder pad.

• Pectoralis major is located along the front of the chest and connects the collarbone to the middle of the chest region.

• Rhomboid major connects the second, third, fourth, and fifth vertebrae to the scapula.

Rotator cuff muscles also have tendons that connect muscle to bone, giving the shoulder its wide range of motion and providing further stability for the joint.2 These are:

• Supraspinatus

• Infraspinatus

• Teres minor

• Subscapularis

Other supportive muscles of the shoulder include the biceps brachii, known as the biceps, the latissimus dorsi, pectoralis minor, and triceps.2 

The shoulder joint also has a fibrocartilaginous piece of connective tissue called the labrum; several fluid-filled sacs called bursae absorb friction, a joint capsule, and a matrix of connective and supportive ligaments.

Where does shoulder pain come from?

Shoulder pain may come from the shoulder joint itself or any of these surrounding structures. Sometimes, shoulder pain does not arise from the shoulder and instead comes from an organ inside the body elsewhere. This is known as referred pain.2

The cause and the type of the shoulder pain are essential to determine as not all shoulder pain is felt equally. Pain coming from the shoulder joint can worsen with activity or movements of the arm or shoulder compared with other causes. For example, pain while playing overhead sports, elevating the arm, or engaging in repetitive activities can vary in type and severity compared to the tight, squeezing sensation accompanying a heart attack.

You may find it beneficial to keep a journal and catalog the type of pain you experience with your shoulder, any activities that aggravate or accompany the pain, the time of day it is felt, and if you have any changes in moving your arm (range of motion).

Common causes of shoulder pain include age and repetitive motion, such as performing overhead motions like painting or throwing a ball.1,3,4 The muscles and tendons of the rotator cuff can become inflamed, and these inflammatory components are irritating to the local soft tissues, resulting in pain. Other common causes include damage to the shoulder muscles, including muscle tears, inflammation of the tendons (tendinitis), torn cartilage, sprains, and more.

However, the causes for shoulder pain are varied3. They will depend on a specific mechanism of injury or trauma or if the pain was preceded (caused by) repetitive movements. Sometimes, the pain is insidious, with no identifiable cause for shoulder pain inside the actual shoulder. This can occur when the source of the pain is coming from somewhere else other than the shoulder, such as an impingement or “pinch” of the nerves from the neck.  Although pain exists in the shoulder region in situations like these, the cause is further up in the body. 

What are the most common shoulder injuries?

About 18 million Americans per year are affected by shoulder pain, according to a 2019 review.4 Rotator cuff tears are the most frequent cause of shoulder pain.2,3,4

Shoulder muscle injuries can result from:

• Traumas: a fall, blow to the shoulder, or a car accident

• Age-related degeneration

• Repetitive overuse

• Repeated overhead use of the shoulder in sports

• Occupations that include vibration

• Constant computer or phone use

• Poor posture

Some other causes of shoulder pain include:

• Autoimmune disease

• Bone spurs

• Broken arm

• Broken collarbone

• Bursitis

• Cervical radiculopathy

• Deconditioning

• Dislocated shoulder

• Frozen shoulder

• Impingement (nerve)

• Impingement (tendon)

• Muscle strain

• Muscle tears

• Myocardial infarction (heart attack)

• Osteoarthritis

• Referred pain from gallbladder or heart disease

• Rotator cuff injury

• Sprains

• Tendinitis

• Thoracic outlet syndrome

• Torn cartilage

When do I see a doctor?

Shoulder pain accompanied by shortness of breath, difficulty breathing, or a sense of tightness in the chest requires immediate medical attention. Call 9-1-1 or emergency medical assistance. You may ask someone to drive you to urgent care or an emergency room if your shoulder pain is caused by an injury and has:

• Intense pain

• Sudden swelling

• A joint that appears deformed

• Sudden and/or severe loss of movement

Make an appointment with your primary care doctor if your shoulder pain has swelling, tenderness, redness, or warmth around the joint.5

Mild shoulder pain often goes away in a day or two. It can be treated at home by avoiding aggravating activities such as heavy lifting, using over-the-counter pain relievers, and icing the affected area. If pain continues beyond self-care measures, is mild to moderate in severity, and lasts for more than a few days, give your chiropractor a call to schedule an appointment for an evaluation.

References

1. American Academy of Orthopaedic Surgeons. “Shoulder pain and common shoulder conditions.” Retrieved June 2021 online from https://orthoinfo.aaos.org/en/diseases--conditions/shoulder-pain-and-common-shoulder-problems

2. Netter, F. H. (1906-1991). Atlas of Human Anatomy. Philadelphia, PA: Saunders/Elsevier, 2014.

3. Miller, M.D., and Thompson, S.R. (2020). DeLee, Drez, & Miller's Orthopaedic Sports Medicine: Principles and Practice. 5th ed. Philadelphia, PA: Elsevier, 2020.

4. Miniato, M.A., Anand, P., Varacallo, M. Anatomy, Shoulder and Upper Limb, Shoulder. [Updated 2020 Jul 31]. StatPearls. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK536933/

5. Mayo Clinic. “Shoulder pain.” Retrieved June 2021 from https://www.mayoclinic.org/symptoms/shoulder-pain/basics/when-to-see-doctor/sym-20050696