This will be described in steps
1. chiro adjustments (thoracic disc, sacrum and once the pain is gone and motion restored scapula then glenohumeral)
2. ice and do broomstick or rope pull exercise.
Here's how: suspend rope overhead. Loop affected arm's wrist in one end. Pull that arm out to the side with the strength of your good arm only (drag the affected arm outward). Repeat reps up to 15 minutes daily for two weeks.
3. Do not sleep with arm raised toward head.
Gonstead chiropractors trained in this procedure are recommended to be sought for care in these cases.
for more info see my thread on rehab/prevention
Information above is not a prescription, not a substitute for a direct exam and care by a competent professional