I have come to situations where I finish exercising, or not even exercising , I lift my right arm, and within the shoulder muscle (Deltoid); the muscle cracks (inside the muscle).

My left shoulder does the same thing, only it doesn't do it that loudly.

Why does my muscles do this?

  • I've heard "muscle sore", "muscle tear", muscle strain", etc etc etc but "muscle cracks" is a new one!
    – Y12K
    Nov 1, 2017 at 4:43

2 Answers 2


Shoulder cracks or clicks are not from the shoulder muscles.

Rather, usually the tendons or a Labral tear are the causes for such noises.

Even if the cracks are not accompanied with pain you should, at the very least, have a competent personal trainer (or even a physical therapist) work with you on your shoulder training.

  • I have my clients do their shoulder presses, shoulder flies etc. at a bit of an anterior angle (slightly in front of them) as suggested by Jeff Cavaliere, PT. This generally gets rid of the clicking and even discomfort.

If you are feeling discomfort/pain with the cracking you should see your medical care provider about it to rule out any injuries.


Shoulder (Synovial Joint) "Cracking"

Until recently experts thought "cracking" had to do with the collapse of air bubbles in the synovial fluid that lubricates joints. New evidence suggests the sound is actually caused by precisely the opposite the formation of a gas-filled cavity when the bones in joints stretch apart.

There's actually a showing the process of joint cavitation -- what it looks like when a synovial joint is "cracking".

Real-Time Visualization of Joint Cavitation

As the bones in the joint separate, negative pressure means gas (likely nitrogen) in the synovial fluid gathers together, resulting in the sudden formation of bubbles along with the cracking noise.


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