Shoulder tendonitis is inflammation of one or more tendons in the shoulder, most commonly in the rotator cuff. It causes pain that typically worsens when you lift your arm overhead or reach behind your back, and it’s one of the most frequent sources of shoulder pain in adults. The condition develops when repetitive motion or overuse irritates the tendons that connect your shoulder muscles to bone, triggering swelling and pain that can range from a mild ache to sharp, movement-stopping discomfort.
Which Tendons Are Involved
Your rotator cuff is a group of four muscles that come together as tendons to form a covering around the ball of your upper arm bone. These tendons work as a team to stabilize the shoulder joint and allow you to rotate your arm in all directions. When one of them becomes inflamed, that’s shoulder tendonitis.
The supraspinatus tendon, which runs along the top of the shoulder, is the one most commonly affected. It sits in a narrow space between two bones, so every time you raise your arm, it can get pinched or compressed. Over time, that repeated compression irritates the tendon and leads to inflammation. The biceps tendon, which attaches the front of your upper arm to the shoulder, is the other frequent culprit.
Tendonitis vs. Tendinosis
These two terms sound similar but describe different stages of tendon trouble. Tendonitis is an acute injury caused by inflammation. You have a swollen, painful tendon, but the tendon’s internal structure is still intact. It responds well to rest and treatment within weeks.
Tendinosis, on the other hand, is the result of degeneration over time. The collagen fibers inside the tendon break down, and the tissue becomes hard, thick, scarred, and rubbery. Some of this damage is only visible under a microscope. Tendinosis typically takes much longer to resolve because the tendon needs to rebuild, not just calm down. Many people who think they have chronic tendonitis actually have tendinosis, which matters because the treatment approach shifts from managing inflammation to encouraging tissue repair.
Common Causes and Risk Factors
Repetitive overhead motion is the primary driver. Sports that involve throwing, swinging, or reaching, like baseball, swimming, tennis, volleyball, and golf, place enormous stress on the rotator cuff with every repetition. Improper technique in any sport is one of the main causes of tissue overload, so it’s not just how often you move but how well you move that matters.
Work-related repetitive motion is just as common a trigger. Painters, movers, roofers, and anyone doing assembly work or operating overhead machinery face elevated risk. Even a single acute injury, like a direct blow to the shoulder or falling on an outstretched arm, can set off tendonitis.
Biology plays a role too. As you age, tendons naturally lose flexibility, making them more vulnerable to irritation and less efficient at recovering from strain. Existing conditions like arthritis add further stress. Skipping a warmup or stretching routine before physical activity also increases your chances, since cold, stiff tendons are more prone to microtrauma.
What Shoulder Tendonitis Feels Like
The hallmark symptom is pain at the front or top of the shoulder that flares when you lift your arm, especially above shoulder height. Reaching into a high cabinet, throwing a ball, or even putting on a jacket can trigger it. The pain often starts as a dull ache after activity and gradually becomes sharper or more persistent over days or weeks.
Night pain is particularly common. Many people notice the shoulder aches more when lying on the affected side, making it hard to find a comfortable sleeping position. You may also feel a clicking or mild catching sensation when moving the arm, along with localized tenderness when you press on the front or outer edge of the shoulder. As the condition progresses, stiffness can develop, and you may unconsciously limit how much you use that arm.
How It’s Diagnosed
Diagnosis usually starts with a physical exam. Your doctor will move your arm into specific positions to see which movements reproduce the pain. Two commonly used tests involve raising the arm forward while the shoulder blade is stabilized or rotating the arm inward at shoulder height. These maneuvers are better at ruling out tendonitis than confirming it. If the tests don’t cause pain, there’s a strong chance the problem lies elsewhere. A negative result on one standard test, for example, drops the probability of a rotator cuff problem from about 45% to just 14%.
If the physical exam is inconclusive or your symptoms suggest a tear rather than inflammation, imaging comes next. Both ultrasound and MRI are effective tools. Ultrasound picks up tendonitis with about 85% sensitivity and 90% overall accuracy compared to MRI. Since ultrasound is less expensive and more widely available, it’s often used as the first imaging step when the main question is whether the tendon is intact. MRI provides more detailed images of soft tissue and is typically reserved for cases where a partial or full tear is suspected.
Treatment and Recovery
Most shoulder tendonitis improves with conservative care. The first step is reducing the load on the tendon: cutting back on the overhead activity that triggered it, icing the shoulder for 15 to 20 minutes several times a day, and using over-the-counter anti-inflammatory medication to manage pain and swelling. Complete immobilization isn’t usually recommended because the shoulder can stiffen quickly, creating a secondary problem.
Physical therapy is the cornerstone of recovery. A structured program focuses on gradually strengthening the rotator cuff muscles and the muscles around the shoulder blade, improving flexibility, and correcting any movement patterns that contributed to the problem. Consistency matters more than intensity. Most people see meaningful improvement within six to eight weeks of regular therapy, though full recovery can take several months depending on severity.
Steroid Injections
Corticosteroid injections are sometimes offered when pain is severe enough to interfere with daily life or prevent you from participating in physical therapy. They work well in the short term. Within the first four to eight weeks, injections provide significantly more pain relief than either placebo or physical therapy alone. But the benefit fades. By 12 to 24 weeks, there’s no detectable difference in pain between people who received injections and those who didn’t. At longer follow-up, injections actually appear less effective for restoring function than other treatments.
Side effects are relatively mild: about 11% of people experience a temporary flare of pain after the injection, and roughly 4% develop minor skin changes at the injection site. The practical takeaway is that injections can be a useful bridge to get pain under control so you can do the rehab work, but they don’t replace the rehab itself.
Preventing Shoulder Tendonitis
If your risk comes from sports, the most effective prevention is technique correction. Working with a coach to refine your throwing mechanics, swim stroke, or overhead press form reduces the repetitive strain that wears tendons down. Warming up before activity and incorporating regular rotator cuff strengthening exercises into your routine keeps the tendons resilient.
For desk workers and anyone with a sedentary job, ergonomics matter more than you might expect. Position your keyboard so your wrists and forearms are in line and your shoulders stay relaxed rather than hunched. If your chair has armrests, set them so your elbows rest close to your body without your shoulders lifting. Keep frequently used items like your phone, stapler, or reference materials within easy reach to minimize repetitive reaching. Most importantly, get up and move throughout the day. Shifting positions, standing periodically, and stretching your arms and shoulders breaks the cycle of static tension that contributes to tendon irritation over time.
For people in physically demanding jobs, pacing overhead work, alternating between tasks that use different muscle groups, and building shoulder strength outside of work hours all help reduce the cumulative load on the rotator cuff.