There are several reasons why your arm may dislocate often. One reason could be because of a previous injury or surgery that has left your arm vulnerable. Another possibility is that you have loose joints which makes it easier for your arm to pop out of place. Genetics also plays a role in whether or not you're more prone to dislocating your arm. If you find that your arm is dislocating frequently, it's important to see a doctor (orthopedist) so they can determine the cause and help you find a solution.