To increase the range of movement available at the shoulder, specifically in lifting the arm sideways away from the body.
Stand sideways/perpendicular to a wall, roughly an arm's breadth away, with the afflicted arm closest to the wall. Feet slightly apart, shoulders relaxed head in a neutral position.
Starting as low on the wall as possible, slowly walk the fingers of the afflicted arm up the wall as far as is bearable with no great discomfort.
Avoid hitching the shoulder or bending the torso away from the wall.
At the limit of pain free movement up the wall, stop and hold this position for 30 seconds whilst breathing slowly and deeply, then slowly walk the fingers back down the wall.
Monitor progress by noting how far up the wall you can manage.
This exercise can also be performed facing the wall directly and lifting the arm directly out in front of the body rather than to the side to increase flexion range of movement at the shoulder.