Hello!
Just to confirm, was that your knee cap or you actual knee joint you dislocated? I've taken care of many people with both, and not once was there any question when a person dislocated their actual knee joint, that they needed to go to the emergency room...Both are horribly painful, but generally, if you straighten your leg fully, a dislocated kneecap will go back in and only feel sore..A dislocated knee joint will be swollen, and you probably won't be able to bear weight on it without someone helping you walk...If it is just your kneecap, at the very least, I'd get a elastic knee brace until I could see an orthopedic doctor...
if you have actually dislocated your knee you really need to see someone. you could have aconnective tissue disorder. it is not normal to dislocate a knee without a significant injury.