Rotator cuff (RC) tears nearly always start on the inside surface of the tendon at the top of the shoulder (the supraspinatus tendon or SSP): this is called a rim-rent or partial tear.
It is often ‘silent’ and very often does not need repair (the shoulder is really good at compensating for a torn tendon, up to a point). However partial tears do get bigger and deeper, so they can become complete or full tears respectively, at which time the shoulder starts to become painful, weak, and often stiff. This is where physiotherapy, injections, and surgery can help.
Related treatment information: