Hi my name is Brandon im 19 years old, i was working out about 3 months ago and i guess i was working to hard and near the end of my work out i noticed everytime i lift my right arm in the air my collar pops up (i believe its the ac joint) it doesnt hurt and i can push it back in when its out it is just scaring me that i might get arthritis later in the future and i dont feel like i should be working out anymore cause i might make it worse, i just want to get it fixxed so when i lift my arm in the air it doesn't pop out .... any help or suggestions would be great. someone please shed some light, cause i have been to the doctor and he said he doesnt know what it is and im going for a mri scan to get a better look.. and thoughts or anyone got the same problem, anything will help..thanks brandon.