Causes Of Shoulder Pain 

Introduction 

Shoulder pain is an issue that affects many people and impacts their quality of life and daily activities. Understanding the causes of shoulder pain is crucial for proper diagnosis and effective treatment. In this article, we will explain the anatomy of the shoulder, the common causes of shoulder pain, and the different types of treatment and preventative measures you can take to protect your shoulder health. 

Anatomy of the shoulder   

The shoulder is a complex system made up of bones, muscles and tissues. Let’s begin by going over some key anatomical terms: 

• Bones: The hard living tissues that make up our skeleton
• Skeletal muscles: Groups of fibres that contract and relax together to create movement 
• Tendons: Tissues that connect muscle to bone
• Ligaments: Tissues that connect bone to bone

The intricate design of the shoulder joint allows us to move our arms in several directions, throw balls, pick up heavy objects, and perform a variety of daily activities with ease and flexibility. However, this also means that the shoulder is prone to numerous issues and injuries. 

The main bones in the shoulder are the upper arm bone (humerus), shoulder blade (scapula), and collarbone (clavicle). The upper arm bone fits into a shallow socket in the shoulder blade, creating a ball-and-socket joint. The collarbone meets a part of the shoulder blade at the acromioclavicular joint. All of these bones are connected and supported by a network of muscles, tendons, and ligaments. The muscles around the shoulder also play a crucial role in keeping it stable and mobile. The rotator cuff is made up of four muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) and is especially important for maintaining shoulder function and movement. 

The anatomy of the shoulder joint. Image taken from emDOCs.net¹

Common causes of shoulder pain 

Muscular causes 

Muscle strains and overuse 

Muscle strain and overuse are frequent causes of shoulder pain. A muscle may become strained when a muscle or tendon is stretched or torn, often due to sudden twisting it pulling or lifting of heavy objects. This strain can cause localised pain, tenderness, and swelling and reduce your range of motion.

Overuse, on the other hand, arises from repetitive motions or prolonged stress on the shoulder muscles. This is often seen in jobs that require repetitive movements or heavy lifting and sports that demand consistent shoulder engagement (such as swimming). Overuse can lead to chronic muscle fatigue, micro-tears in the muscle fibres, and inflammation, which all contribute to persistent shoulder pain. 

Rotator cuff injuries 

Rotator cuff injuries usually develop over several years. They are most often caused by repeated wear and tear due to repetitive overhead movements, such as lifting weights, swimming, or throwing heavy objects.² However, tears or inflammation in the rotator cuff can also result from sudden trauma, such as a fall or a direct injury. Rotator cuff injuries often cause persistent shoulder pain, weakness, and difficulty in raising the arm. 

Frozen shoulder 

Frozen shoulder (or adhesive capsulitis) is a condition that causes persistent pain and stiffness and severely restricts shoulder movement. A frozen shoulder causes the shoulder capsule to thicken and tighten, limiting the space for the upper arm bone's movement. This leads to a significant reduction in the shoulder's range of motion and makes it difficult to perform everyday tasks. The development and resolution of frozen shoulder is typically slow and involves three distinct stages: freezing, frozen and thawing. 

While the exact cause of a frozen shoulder is unclear, certain factors like age, gender, diabetes, and prolonged immobility can increase your risk of developing it. 

Structural causes 

Osteoarthritis 

Osteoarthritis in the shoulder occurs when the protective cartilage at the ends of bones wears down over time. This may result from the normal ageing process or previous shoulder injuries. As the cartilage wears away, the exposed shoulder bones may rub against each other, causing pain, stiffness, and reduced mobility. Osteoarthritis is more common in older adults but can also occur in younger individuals, especially if they have had shoulder injuries or overuse. 

Rheumatoid arthritis 

Rheumatoid arthritis is an autoimmune condition in which the body's immune system mistakenly attacks the joints. This can cause the lining of the shoulder joint to become inflamed, leading to pain, swelling, and stiffness. Unlike osteoarthritis, rheumatoid arthritis can affect people of all ages and often affects both shoulders at the same time.  

Labral tears 

The labrum is a piece of cartilage that lines the shoulder socket and helps keep the ball of the upper arm bone in place. Tears in the labrum can be caused by sudden injury or repetitive shoulder motions. Athletes involved in sports with overhead movements (such as baseball pitchers) are particularly susceptible. Labral tears can cause pain, a catching or locking sensation, and instability in the shoulder. 

Fractures and dislocations 

Fractures or dislocations in the bones of the shoulder are commonly caused by accidents, falls, or trauma. Whilst fractures involve a break in a bone, dislocations happen when a bone is forced out of its normal position. Both types of injury cause severe pain, swelling, bruising, and limited mobility and require immediate medical attention to avoid any long-term complications. 

Nerve-related causes 

Pinched nerves (cervical radiculopathy) 

Cervical radiculopathy refers to the pinching or irritation of nerves in the neck (or cervical spine).³ This can cause pain that radiates into the shoulder, down the arm, and sometimes into the hand. Common causes of cervical radiculopathy include herniated discs or bone spurs in the neck, leading to pressure on the nerve roots, pain, and numbness. 

Brachial plexus injuries 

The brachial plexus is a network of nerves that control movements and sensations in the shoulder, arm, and hand.⁴ These injuries are often caused by trauma or excessive stretching and can result in shoulder pain, weakness, numbness, and impair the function of the affected limb. 

Other causes 

• Bursitis: Bursitis occurs when the bursa, a small fluid-filled sac that cushions and protects the shoulder joint, becomes inflamed.
• Tendinitis: Tendinitis refers to the inflammation or irritation of tendons around the shoulder joint and is often caused by overuse or repetitive motions. 
• Referred pain from neck or upper back: Sometimes, pain originating from the neck or upper back can radiate to the shoulder, giving the sensation of shoulder pain. This is usually due to underlying issues like muscle strain, nerve compression, or joint problems.
• Systemic illnesses: Rarely, systemic conditions such as ankylosing spondylitis or even diaphragm irritation can cause pain in the shoulder.⁵

Risk factors for shoulder pain 

• Age and degeneration: As individuals age, the risk of developing shoulder pain due to wear and tear on the joint and tissues increases.
• Physical activity and sports: Engagement in high-impact sports (for example, rugby) or activities that involve repetitive shoulder movements (for example, tennis) can strain the muscles and increase the risk of injuries.
• Occupation and repetitive movements: Certain jobs that require repetitive shoulder movements or heavy lifting can put excessive stress on the shoulder, leading to pain and injuries.
• Poor posture: Maintaining poor posture, especially while working or using electronic devices, can strain the muscles and ligaments in the shoulder area.
• Genetics and family history: Some individuals may be genetically predisposed to conditions like osteoarthritis that can contribute to shoulder pain.

Diagnosis of shoulder pain

A thorough medical history and physical examination by a healthcare professional are crucial in identifying the cause and location of shoulder pain. X-rays, MRI, and ultrasound imaging may be ordered to visualise the bones, soft tissues, and structures in the shoulder to diagnose fractures, tears, or other abnormalities.⁶ Further, electromyography (EMG) and nerve conduction studies are further tests that can be performed to evaluate nerve function and identify nerve-related issues contributing to shoulder pain. 

In some cases, blood tests may be conducted to rule out systemic conditions that could be causing your shoulder pain. 

Treating shoulder pain

Conservative approaches

• Resting, icing, or elevating the affected shoulder can provide immediate relief and reduce inflammation. 
• Physical therapy can help target muscle strength and flexibility, reducing pain and helping overall shoulder functionality.
• Pain medications and anti-inflammatories are often used to manage discomfort and inflammation. 
• Lifestyle modifications, such as adjusting activities and maintaining good posture, are essential for long-term relief.

Medical interventions

• Corticosteroid injections can provide targeted pain relief and reduce inflammation in the shoulder and are specifically useful for treating frozen shoulder and rotator cuff tendonitis. They tend to take around 5 days to start working, but the pain relief effects can last for several months.⁷
• Platelet-rich plasma (PRP) therapy is another medical option. It uses the patient's own platelets (blood cells) to promote healing and alleviate pain in the affected area.

Surgical options

In severe cases, surgical options may be considered for shoulder pain. Arthroscopic surgery involves using a minimally invasive approach to diagnose and treat shoulder conditions. However, open surgery may be necessary for more extensive repairs. In severe cases of joint damage, joint replacement surgery may be the best course of action. The choice of treatment depends on your individual condition, preferences, and your doctor's recommendations.

Preventative measures

Maintaining good posture and stretching

It is important to be mindful of how you sit and stand and to avoid slouching or hunching. By doing so, you minimise unnecessary stress on your shoulder muscles and help prevent pain or discomfort. Additionally, regularly performing exercises that strengthen and stretch your shoulder muscles is highly beneficial in enhancing muscle stability and flexibility.

Ergonomics at work and home

Prioritising ergonomics both at work and in your home environment is vital for your shoulder health. Ensure that your work station is set up in a way that supports a neutral shoulder position and minimises shoulder strain during daily activities. This includes adjusting the height of your chair, desk, and computer monitor to maintain a comfortable natural posture.

Avoiding shoulder overuse and repetitive motions

Whether it's during work, sports, or any physical activity, taking regular breaks and modifying activities can prevent excessive strain and ultimately lower your risk of developing shoulder pain. By listening to your body and not pushing it beyond its limits, you provide your shoulders the rest and recovery time they need to stay healthy.

Regular check-ups and early intervention

Regular check-ups with a healthcare professional, even when you're not experiencing noticeable shoulder issues, are highly advisable. These routine check-ups can help identify any potential shoulder problems early on before they escalate into severe issues. 

Summary

Understanding the causes of shoulder pain is essential for its effective treatment and prevention. By being aware of the potential causes of shoulder pain, we can take proactive steps to maintain our shoulder health and seek appropriate medical care when needed. Whether it's through lifestyle modifications, exercises, or medical interventions, there are ways to alleviate shoulder pain and improve our overall quality of life.