Shoulder pain may be caused by different anatomical structures like the: tendons, ligaments [capsula], and joints.
The most common dx is the “rotator cuff”. I am not going to describe it here—see separate section.
The second most popular dx is “bursitis”. This condition is very vague. You can never know for sure that it is exactly the bursa that is inflamed [to differentiate it from tendinitis in real life is very difficult].
There are also labrum injuries, instability, true ostheoarthrosis [not an “itis”], etc.
But I want to bring your attention to another structure that can mimic anything, including all the mentioned above conditions That is the AC, [acromio-clavicular] joint. This structure is theoretically not movable, just like a sacro-iliac joint. In real life it is not the case.
I suggest you go to the rotator cuff sdm, where I shall describe this matter in further detail, and it may answer many of your questions.
