Strengthen Shoulder from injury

rciszek

Years ago I dislocated my shoulder in a fall. Since then I have shoulder stiffness and pain periodically which doesn't bother me. I have had an increase in pain in the last week and a half. Didn't think about it but during my run my dog decided to go the other direction and jerked my arm. Evidently it popped my shoulder back out again. Had it popped back in but it seems to be popping out more frequently. What moves would be the best to strengthen up my shoulder to prevent it?