hi thank you for asking your concern and welcome to hcm. there are 3-4 common conditions which can present like this. 1. frozen shoulder - this is the most common condition that we see if there is no history of recent trauma or some heavy work. 2. rotator cuff injury as you mentioned is generally precedes with some kind of trauma and it is painful as frozen shoulder 3. arthritis of shoulder joint 4. acute joint pain for any of this condition treatment is almost same. first i would suggest you to consult physiotherapyst to arrive at a diagnosis. in such conditions it is must to check for diabetes because frozen shoulder is the most common complication of diabetes. for immediate relief i would advice tablet ibuprofen of paracetamol one tab three times a day and hot compresses. i hope i answered your concern and feel free to ask any doubts thank you and regards dr. abhijit