Muscles atrophy due to lack of use. When muscles atrophy, the load is taken by the tendons, which because of the strain then leads to inflammation, e.g. tunnel carpal, tennis elbow, shoulder pain, etc
My wife saw an acupuncturist who treated her for tunnel carpal and tennis elbow (she doesn't play tennis.) For treating the pain he used acupuncture, but she was told to exercise her forearms for tunnel carpal, and biceps and triceps for tennis elbow. Once the atrophied muscles are strong enough to take most of the load, there will be pain relief. So when my shoulders started hurting due to atrophy, I exercised the different muscles in my shoulders slowly though it was painful. The pain disappeared after a couple of months. It is counter intuitive but it works.
With a torn rotator cuff, you probably should see a doctor and get a referral to a physical therapist. Once you learn which exercises to do, you can implement them at home.
To sum it up: You may want to find help on healing frequencies and exercise very slowly and carefully, nothing intense, two to three minutes a few times a day. If you need a doctor, please see a doctor or sport therapist or physical therapist.
I am not a doctor or sports therapist. I am just sharing my personal experience that you may find useful and take personal responsibility in implementing it if you choose to.
If you want more details, please check the link: