I can’t count the number of times that I break the unfortunate news to a patient that they tore their rotator cuff and their response is, “How could this be? I didn’t do anything to hurt my shoulder!” They are not wrong. And yet there we are, staring at the torn tendon on an MRI of their shoulder in my office. Find out why.

This is because most rotator cuff tears diagnosed every year are degenerative, meaning they are caused by daily wear and tear, not a one-time injury. This might explain why 1 out of every 5 people over the age of 50 and 1 out of every 2 people over the age of 80 have a rotator cuff tear. Of the 200 or so rotator cuff repairs that I performed in 2023, fewer than 10% of those patients can describe or recall an actual injury to their shoulder.

So how do these degenerative rotator cuff tears happen? At the molecular level, this is a complicated process, but in broad strokes, it boils down to two major factors:

1. Mechanical “Impingement”: meaning that over the years, the undersurface of the bony ceiling of the shoulder, a part of the shoulder blade called the ‘acromion’ can rub against the top of the rotator cuff, causing it to tear off bone. The tendon often looks like a carpet in this area that has seen heavy foot traffic: torn or shredded fibers and irregular appearance.
2. Diminished blood supply to the tendon: as we reach mature adulthood, the blood supply to the rotator cuff tendons is not as robust. This means the tendons do not receive the oxygen and nutrition they require to withstand the strain placed on them throughout our daily activities. This causes the tendon to weaken, sometimes tearing off the bone to which it must be attached to lift the arm without pain and have strength and endurance for lifting and other activities.

It is rarely one or the other of these causes from person to person, rather a combination of the two. Some people may have a certain shape to the bony ceiling of the shoulder (acromion) that predisposes them to degenerative rotator cuff tears by mode #1, whereas certain diseases (high cholesterol), habits (smoking) or jobs (construction, electrician) can lead to rotator cuff tears by mode #2. Schedule a consultation to learn more about what you can do to keep your shoulder healthy or if you have symptoms of a rotator cuff tear.