MY LEFT KNEE

HELLO, MY NAME IS MEGAN TAYLOR AND I HAVE HAD KNEE TROUBLE SINCE I WAS 11 AND NOW I AM 15. I WAS RUNNING DOWN SOME STEPS AND FELL AND TWISTED IT THE WRONG WAY I WAS ON CRUTCHES FOR ABOUT A MONTH BUT NOW WHEN I WALK OR DO ANY KIND OF SPORT OR AND STRENOUS ACTIVITY IT BOTHERS ME. I HATE IT WHAT CAN I HAVE DONE, SHOULD I WEAR A KNEE BRACE, I REALLY ENJOY SPORTS AND OTHER OUTDOOR ACTIVITY WELL I HOPE SOMEONE CAN HELP ME. THANKS VERY MUCH, MEGAN TAYLOR