patella dislocation

good morning, I am an active person and recently I had an accident during my martial arts class, my left kneecap was dislocated and I was put in a cast for a month, I think I have bad knees, im scared that it might happen again or might happen to my other knee, pls tell me what kind of knee protector that I need and if you have some exercises for streghten the muscles around the patella,pls tell me via email.my email is [email protected] for your time sircarlo