Rotator cuff tears result from either a sudden injury or gradual wear on the tendons that hold your shoulder together. Most tears are degenerative, meaning they develop slowly over months or years as the tendon weakens from repetitive use, reduced blood supply, and age-related changes. Acute tears from a single event, like a fall, are less common but do happen.
How the Rotator Cuff Works
Your rotator cuff is a group of four tendons that wrap around the ball of your shoulder joint, keeping it centered in its socket. These tendons connect muscles in your shoulder blade to the top of your upper arm bone, and they work together every time you lift, reach, or rotate your arm. The supraspinatus tendon, which runs along the top of the shoulder, tears most often because it sits in a narrow gap between two bones where it’s vulnerable to compression.
Sudden Tears From Injury
An acute rotator cuff tear happens when a single force overwhelms the tendon. Falling on an outstretched arm is one of the most common causes. Lifting something heavy with a jerking motion, catching a falling object, or bracing yourself during a car accident can also rupture a tendon instantly. These traumatic tears often involve a sharp, immediate pain and sudden weakness in the arm.
That said, many “sudden” tears aren’t purely traumatic. A tendon that’s already weakened from years of wear may finally give way during a movement that wouldn’t damage a healthy tendon. A 60-year-old who tears a rotator cuff while lifting a suitcase likely had degeneration already underway. The injury was just the final event.
Degenerative Wear Over Time
The majority of rotator cuff tears develop gradually. This process starts with microscopic damage to collagen fibers in the tendon, often years before any symptoms appear. Two forces drive this degeneration: repetitive stress and declining blood supply.
The supraspinatus tendon has a “critical zone” near where it attaches to bone that receives relatively little blood flow. As you age, that blood supply decreases further, which means the tendon can’t repair everyday micro-damage as efficiently. Small areas of damage accumulate, the tendon thins, and eventually a partial tear forms. Over time, partial tears can progress to full-thickness tears, where the tendon pulls completely away from the bone.
Once a tendon tears and retracts, the muscle it’s attached to begins to deteriorate. Without the mechanical load of normal use, the muscle shrinks, fat infiltrates the tissue, and scar-like fibrosis develops. This stiffening of the muscle actually increases tension on the remaining tendon, which can inhibit healing and make repair more difficult the longer a tear goes untreated. The muscle fibers themselves shift from fast-twitch to slow-twitch types and lose significant size, changes that may not fully reverse even after surgical repair.
Why Age Is the Biggest Risk Factor
Rotator cuff tears are rare in people under 40 and increasingly common with each decade after that. By age 60, a substantial portion of the population has some degree of rotator cuff tearing, and many of those tears cause no symptoms at all. Imaging studies consistently show that the prevalence of tears rises steeply with age, even in people who’ve never had shoulder pain.
Not all of these tears stay painless. Research tracking asymptomatic tears over time found that larger tears are more likely to become painful in the short term. Among full-thickness tears that did become symptomatic, 18% had grown by more than 5 millimeters, and 40% of partial-thickness tears had progressed to full-thickness. In other words, a painless tear today can quietly enlarge and eventually start causing problems.
Overhead Work and Repetitive Use
Jobs that require overhead work carry two to three times the risk of shoulder injury compared to other occupations. Painters, electricians, carpenters, warehouse workers, and anyone regularly reaching above shoulder height is at elevated risk. The threshold is lower than many people expect: working with your arms at 90 degrees or higher for more than 10% of a work shift can double your risk of a shoulder injury.
The anatomy explains why. The space between the top of your arm bone and the bony arch above it (the subacromial space) gets smaller as you raise your arm. It’s narrowest between 60 and 90 degrees of elevation, and the tendon is most likely to get pinched between 95 and 106 degrees. Every overhead reach compresses the supraspinatus tendon in that tight gap. Over thousands of repetitions, this mechanical impingement frays the tendon fibers and accelerates degeneration. Ergonomic guidelines recommend keeping the upper arm below 60 degrees of elevation when possible and limiting overhead tool weight to under 1.25 kilograms during extended shifts.
Athletes face similar mechanics. Baseball pitchers, swimmers, tennis players, and volleyball players load their rotator cuffs with high-velocity, repetitive overhead motions. The combination of speed and repetition creates both impingement forces and tensile strain on the tendons.
Other Contributing Factors
Some people are structurally more prone to tears. A hooked or curved acromion (the bony ridge above the rotator cuff) narrows the subacromial space and increases impingement with normal arm movements. Bone spurs that develop on the underside of the acromion with age create the same problem, physically abrading the tendon during overhead motion.
Smoking reduces blood flow to tendons and impairs the body’s ability to repair tissue, which accelerates degeneration. Genetics also play a role. If a close family member has had a rotator cuff tear, your own risk is higher, likely due to inherited differences in tendon structure, collagen quality, or shoulder anatomy.
Your dominant arm is more frequently affected, which reinforces that cumulative use matters. A right-handed person puts more repetitive load on their right shoulder across a lifetime of daily tasks, and that shoulder is more likely to develop a tear.
Why Some Tears Hurt and Others Don’t
One of the more counterintuitive facts about rotator cuff tears is that tear size doesn’t always predict pain. Some people with large, full-thickness tears have minimal discomfort, while others with small partial tears experience significant pain. The difference likely involves inflammation around the tear, the speed at which the tear developed, and whether surrounding muscles can compensate for the damaged tendon.
Tears that develop very slowly give the body time to recruit other muscles to stabilize the shoulder. This is why so many degenerative tears are discovered incidentally on imaging done for another reason. Acute tears, by contrast, cause sudden pain because the shoulder hasn’t had time to adapt, and the inflammatory response is immediate.