You may have a large irreparable tear in the rotator cuff tendons in your shoulder.
Typically this leads to poor shoulder function. Difficulty with lifting the arm up, loss of strength and pain.
You may find that you can lift the arm with the other hand and then hold it up high but it collapses as you lower it.
This is because the Deltoid muscle is trying to work the shoulder but cannot do it effectively because the rotator cuff that usually holds the shoulder in the correct position whilst the deltoid lifts the arm is not functioning
The Solution?
One solution is the reverse shoulder replacement. this works by allowing the deltoid muscle to lift the arm around a ball joint that is now attached to the shoulder blade- The opposite to a natural shoulder
The effect is to allow comfortable movement, often allowing near full elevation (lifting the arm forward) and Abduction (lifting the arm sideways)
There is usually limitation to getting the hand behind the back but the movement should be sufficient to allow comfortable tucking in of a shirt or blouse
It should be stressed that this is NOT a new shoulder. It allows a very poorly functioning shoulder to work much better but can never be as good as a young shoulder with intact rotator cuff