14 Most Common Shoulder Pain Causes

2. Tendinitis

Tendinitis refers to swelling or irritation of a tendon, the thick band of tissue that connects muscle to bone. In the shoulder, it most often involves the rotator cuff or the biceps tendon, both of which help guide and stabilize arm movement. Frequent lifting, throwing, or overhead reaching places ongoing stress on the tendon.

Over time, this repeated load causes small areas of tissue irritation. As the irritation builds, the tendon becomes inflamed and more sensitive to movement. Pain is the most common symptom. It often becomes noticeable when lifting the arm, reaching overhead, or lying on the affected side because these positions increase tension on the irritated tendon.

Risk increases with activities that involve repetitive shoulder use, such as certain sports or manual labor. Aging also plays a role. As tendons gradually lose flexibility and resilience over time, they become more vulnerable to irritation under stress.

3. Tendon Tears

Tendon tears occur when a tendon partially or completely separates from the bone. In the shoulder, this most often involves the rotator cuff, a group of tendons that stabilize the joint and help lift and rotate the arm. A tear can develop suddenly or gradually.

A fall, heavy lifting, or a forceful pull may place more tension on the tendon than it can tolerate, causing it to split or detach. In other cases, repeated strain over time leads to gradual tissue breakdown. As people age, tendons naturally lose strength and elasticity, which increases the risk of tearing even with routine movements.

The extent of damage can vary. A partial tear disrupts some tendon fibers but leaves the structure partly attached to the bone. A complete tear fully separates the tendon from the bone, often resulting in greater weakness and loss of function.

Pain and weakness are common signs. Discomfort often appears when lifting the arm, reaching overhead, or moving it away from the body because these actions require rotator cuff support. Some people notice pain along the outer upper arm, and symptoms may worsen at night, especially when lying on the affected side.

4. Impingement

Impingement occurs when a shoulder tendon becomes compressed and repeatedly rubs against nearby bone or surrounding tissue. This most often involves the rotator cuff, which helps stabilize the joint and control arm movement. When the arm lifts overhead, the space within the shoulder narrows.

If the tendon passes through this tight space, it can become pinched. Repeated compression leads to irritation and inflammation, which gradually increases pain. The discomfort is commonly felt on the top or outer part of the shoulder. It often becomes sharper when reaching upward, throwing, or performing activities such as swimming because these motions further narrow the space and increase tendon contact.

Impingement may begin after an injury that alters shoulder mechanics. It can also develop gradually from repeated overhead activity at work or in sports. Poor posture, such as rounded shoulders, can shift joint alignment and reduce the space available for the tendon.

5. Instability

Shoulder instability occurs when the ball at the top of the upper arm does not remain securely centered within its socket. The shoulder is designed for a wide range of motion, which allows flexible movement but also makes the joint more vulnerable to injury.

When the muscles, ligaments, or cartilage that support the joint become stretched or torn, the ball can shift excessively within the socket. Instability often begins after a fall or sports injury. In a full dislocation, the ball moves completely out of the socket. In a partial dislocation, or subluxation, it slips out and then returns to position on its own.

Once these structures lose tension or integrity, the joint becomes less secure during movement. As a result, people may experience pain, weakness, or a sensation that the shoulder might “give way.” Certain arm positions may feel unsafe, leading them to avoid overhead or outward movements.

6. Arthritis

Arthritis is a common cause of shoulder pain. It develops when a joint becomes inflamed or when the smooth cartilage covering the ends of the bones gradually wears down. Cartilage normally allows the joint to move with minimal friction. As it thins or breaks down, the protective cushion between the bones decreases.

This can cause the bones to rub against each other, leading to pain, stiffness, and reduced range of motion. Osteoarthritis is the most common type affecting the shoulder. It usually develops over time as the joint experiences age-related wear or repeated mechanical stress. Both the main shoulder joint and the joint at the top of the shoulder can be involved, which may gradually limit movement and increase discomfort during daily activities.

Other forms of arthritis can also affect the shoulder. In inflammatory types, the immune system targets the joint lining, triggering swelling, warmth, and stiffness that can interfere with normal movement. Septic arthritis occurs when an infection enters the joint space, leading to rapid inflammation and pain, although this form is less common.

7. Fracture

A shoulder fracture is a break in one of the bones that form the shoulder joint. Most injuries affect the upper part of the arm bone near the shoulder. This type of injury is known as a proximal humerus fracture. Fractures usually occur after a significant force is applied to the area. A fall onto an outstretched hand or directly onto the shoulder is a common cause.

Motor vehicle accidents and sports injuries can also generate enough impact to break the bone. When a person falls on the hand, the force travels upward through the arm and concentrates near the shoulder, which can cause the bone to crack or break. Symptoms often begin immediately after the injury.

The shoulder may become swollen or bruised as blood and fluid collect around the damaged tissue. Movement becomes painful because the broken bone can shift with motion. In more severe cases, the shoulder may appear deformed, or the person may be unable to lift the arm at all due to pain and structural instability.

8. Sporting Injury

Sports place repeated and sometimes sudden stress on the shoulder joint. Fast throwing motions, heavy lifting, and hard falls generate strong forces that travel through the muscles, tendons, ligaments, and bones. Contact sports like football and hockey increase the risk of joint injuries due to direct blows that can misalign the joint or strain nearby tissues.

A sprain occurs when ligaments, which connect bone to bone, are stretched or torn. A strain affects a muscle or tendon, which connects muscle to bone. In both cases, excessive force exceeds the tissue’s normal capacity, leading to microscopic or larger tears. This triggers inflammation, resulting in pain, swelling, and difficulty moving the arm.

Rotator cuff problems often develop from repeated overhead motion. Athletes such as baseball pitchers, swimmers, and tennis players perform the same high-range movements many times, which can irritate or overload the tendons. Ongoing stress may cause inflammation or partial tears, leading to weakness and pain when lifting or rotating the arm.

9. Rotator Cuff Tear

A rotator cuff tear is a common cause of shoulder pain. The rotator cuff is made up of muscles and tendons that stabilize the shoulder joint and keep the upper arm bone centered in the socket during movement. When one of these tendons becomes irritated, weakened, or overloaded, it can partially or completely tear.

Repeated overhead motion places ongoing stress on the tendons, which can lead to small areas of degeneration over time. As the tissue weakens, even routine movements may cause further damage. A tear can also occur suddenly after a fall or when lifting something heavy, especially if the tendon has already been worn down.

The risk increases with age, particularly after 40, because tendon elasticity and blood supply tend to decline. Pain often begins along the top of the shoulder or upper arm. Some people notice weakness because the damaged tendon cannot generate normal force. A clicking or catching sensation may occur if the tendon no longer glides smoothly.

10. Untreated Injuries

A minor shoulder injury can develop into a long-term problem when it does not receive proper care. Sprains, strains, and small tears may seem mild at first, and pain can decrease within a few days. However, reduced pain does not always mean the tissue has fully healed. Microscopic damage may still be present within muscles, tendons, or ligaments.

If a person continues to use the shoulder without adequate rest or rehabilitation, repeated stress can interfere with normal repair. Ongoing strain may enlarge a small tendon tear or prolong inflammation inside the joint. As swelling persists, joint space can become crowded, which limits smooth movement and gradually leads to stiffness.

For example, a minor tear in the Rotator cuff may widen over time if overhead activity continues without support or strengthening. As the tear enlarges, the shoulder may lose stability and strength, increasing discomfort with lifting or reaching. Untreated dislocations or separations can also lead to repeated instability.

The shoulder joint is naturally designed to allow a wide range of motion, which makes it more dependent on surrounding soft tissues for support. If these structures do not heal correctly, the upper arm bone may slip out of position more easily during future movements.

11. Lifting Overhead

Lifting the arm above shoulder level places significant stress on the shoulder joint. Although the shoulder allows a wide range of motion, it depends heavily on surrounding soft tissues for stability. When a person repeatedly performs overhead movements, these tissues are exposed to ongoing mechanical strain.

The Rotator cuff plays a central role in stabilizing the upper arm bone within the shoulder socket. During repeated overhead lifting, the tendons of the rotator cuff can become compressed beneath a small bony arch at the top of the shoulder. This repeated pinching narrows the available space and irritates the tendons. As irritation continues, inflammation may develop, leading to swelling and pain.

Early signs often include discomfort when reaching upward, brushing hair, or placing objects on a shelf. The pain is commonly felt along the front or side of the shoulder and may extend down the upper arm, usually stopping above the elbow.

12. Adhesive Capsulitis

Adhesive capsulitis, often called frozen shoulder, develops when the capsule that surrounds the shoulder joint becomes inflamed and progressively tight. As the capsule thickens and contracts, it restricts the normal gliding motion of the joint, which steadily limits how far the arm can move. The condition usually begins with a dull or aching pain in the shoulder.

As inflammation continues and the capsule tightens further, stiffness increases and range of motion declines. Over time, simple tasks such as reaching overhead, fastening a seatbelt, or placing a hand behind the back become difficult because the joint can no longer move freely in multiple directions. It most often affects adults between ages 40 and 70, and women develop it more often than men.

Risk factors include diabetes, thyroid problems, recent shoulder injury or surgery, and long periods of reduced shoulder movement. Limited use of the joint can contribute to further tightening of the capsule, which reinforces the cycle of stiffness.

13. Failing to Warm Up Before Exercise

Skipping a warm-up places sudden stress on the shoulder joint, which has a wide range of motion and relies on coordinated muscle support for stability. When a person begins exercise without preparation, the muscles and tendons that guide and protect the joint may not be ready to handle the load.

Cold muscles are less flexible and respond poorly to rapid or heavy movements. If force is applied too quickly, the rotator cuff muscles and tendons that hold the shoulder in place can become strained. This strain may lead to soreness, mild swelling, or small tissue injuries that accumulate over time. A proper warm-up gradually increases blood flow to the shoulder muscles and improves joint control.

As circulation rises, tissues become more pliable and better able to manage stress. Simple movements such as arm circles, light resistance band exercises, or slow shoulder rolls help activate the supporting muscles before more demanding activity begins. Risk increases when a person switches activities without a gradual buildup. Moving directly from walking to weight training can strain the shoulder if the muscles aren’t prepared for that level of stress.

14. Not Resting a Mild Injury

A mild shoulder injury may begin as a small strain, light sprain, or slight tendon irritation. At first, the discomfort can seem minor, and many people continue lifting, reaching, or playing sports, expecting the pain to resolve on its own. However, the shoulder’s muscles, tendons, and ligaments require time to repair.

When the joint is repeatedly stressed before healing occurs, the irritated tissue remains inflamed. Ongoing strain can increase swelling and prolong pain rather than allowing recovery to progress. As irritation continues, pain often becomes more noticeable with movement and may travel along the outside of the upper arm.

Some people also experience weakness or stiffness because the inflamed tissues cannot function smoothly. Soft tissue injuries commonly take several weeks to improve, and more significant damage may require even longer.