How did you dislocate your knee cap? How old are you? I am assuming you mean you dislocated your knee cap?
The reason I ask: depending upon whether it was traumatic or otherwise, and dependent upon you age, the treatment will slightly vary.
Most importantly, you need to decrease the swelling. Use ice - 10 minutes on every hour. Do not use heat! It can take up to 2-3 weeks for the majority of the swelling to go down.
The swelling inside your knee will be stopping the knee bending. Until that fully goes down, you will have a limited knee bend. I had knee surgery when I was 14 and 15 years of age, and sometimes it swells up according to what I do or if I twist it the wrong way. That was 22 years ago!! Swelling inside the knee (even only a teaspoon of fluid) will also affect the strength of the thigh muscles, so decreasing the swelling in the knee is a real priority.
Returning to sports: that is a tough question - depends upon the type of sport. You need to strengthen the inner thigh muscles and stretch the outer thigh muscles. Tough to really describe and you should get a physical therapy evaluation to teach you this correctly. To be technical, you need to build up the vastus medialis oblique muscle and stretch out the iliotibial band. This is assuming that your knee cap (patella) dislocated inwards and not outwards.
Try to wean yourself off the brace slowly and only use for sporting activities or when you know you will be on it for long periods. Long term use of the brace will actually weaken the thigh muscles, making your problem worse.
I hope this helps.
15 years experience as a physical therapist and sports massage therapist