Although most shoulder problems are relatively short-lived, pain in the shoulder 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 (AC) joint. On the other end of the clavicle is the sternum, commonly known as the breastbone, which forms another joint, the sternoclavicular (SC) 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! With all that mobility, it is also the most unstable joint the in the body! Because of this, a combination of muscles and ligaments working in harmony to achieve proper, range -of-motion is needed.
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. Some of the common shoulder muscles are as follows:
- 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 minor connects the second, third, fourth, and fifth vertebrae to the scapula.
The rotator cuff muscles are extremely important, providing stability and allowing the shoulder its wide range of motion2. The following are the four rotator cuff muscles:
- Teres minor
Other important muscles of the shoulder complex 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 Believe it or not, the gall bladder can refer pain to the right shoulder!
Since the joint is so complex, determining the cause or causes are very important. Pain coming from the shoulder 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 the neck or shoulder blade. Muscle imbalance and overuse can also result in shoulder pain. Many times, the pain in the shoulder is the result of dysfunction elsewhere!
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
- Cervical radiculopathy
- Dislocated shoulder
- Frozen shoulder
- Impingement (nerve)
- Impingement (tendon)
- Muscle strain
- Muscle tears
- Myocardial infarction (heart attack)
- Referred pain from gallbladder or heart disease
- Rotator cuff injury
- 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 MN Spine and Sport in Woodbury a call to schedule an appointment for an evaluation.