I was playing racquetball the other day and I went to hit an overhead shot and it felt like my shoulder popped out. When it was popped out, my shoulder was numb, I felt like I couldn't move my shoulder/arm. But, a couple of seconds after it popped out, it popped back in automatically. I did not do anything; I just held it trying not to cry in front of my opponent.
This is not the first time it happened, but it only happens once every 6 months or so. Every time it happens, the next couple of days are miserable. It hurts like hell to move my arm and it take at least a month or so for the pain to go away.
Any ideas on how to prevent this or why this is happening?