I am 17 years old and i am a girl. I really want to be a good taekwondo fighter, but not only a fighter. I love doing it more than I can say even if i am not that good. My left knee is so weak and painful when I do things like sitting, running, and kicks. I am having a hard time. Can any one please tell me what to do rather than stop doing it? I am really scared I do not want to stop doing taekwondo please.
First off, I hear you. I was in your position once after my knee locked up in excruciating pain while running one day in my early 30's. I was training for a marathon. I went to see a medical doctor who specialized in sports medicine. I was really upset that I might be essentially cripple, and I really wanted to be able to run that marathon.
He diagnosed me with patellofemoral pain syndrome. And I was prescribed exercises to do at home to rehab and strengthen the knee. They really did help, but my knee will never be as good as it was in my teens. I'll never run a marathon, I don't think, but I can run a 10k just fine. There are limits.
The point is this: 1) See a medical doctor to get examined and diagnosed. 2) Get treatment and/or rehab. 3) You will probably realize that you will always have issues with your knees, but you'll be able to avoid the worst of the problems so long as you're careful and are aware of your limitations. Your doctor and/or rehab specialists will help you figure that out.
That being said, Taekwondo is particularly bad for knees. I have a black belt in TKD, by the way. And I actually blame my knee problems on my TKD training back in my teens. In particular, watch out for how far you extend your knees. You don't ever want to hyper-extend the knees (going further than lock position).
Pay attention to any slight pain your knees are feeling, and if you feel any, that's when you need to take a break immediately and have ice packs standing by (bring an insulated freezer bag with ice packs in it to every class). Your instructor will need to be told of your condition, and he/she has to be okay with you stepping out immediately.
I also recommend taking a week or two off whenever you feel pain, even if it's small, starting immediately after you feel it. Ice it up immediately. Give it rest. Don't go back the next day. Don't go back for at least one whole week. And don't practice kicks at home when you're supposed to be resting.
Your doctor and/or physical therapist will likely prescribe exercises you need to do at home. These will help strengthen your knee. You're going to need to do these exercises religiously, every day or every other day as is prescribed. And do them right before class. They'll provide a certain degree of immunity to most problems.
The exercises won't work perfectly. You'll still get knee problems if you go too hard or too long. That's okay. It's just about knowing your limitations, that's all. And at first, you won't know, so you're going to feel pain again. That's normal. That's just finding your limits. It takes time to figure those limits out.
There are so many conditions of the knee that you can have, by the way. Some are treatable with strengthening exercises like I mentioned. Others may require surgery. Others may require certain medications. You won't know until you're diagnosed. So you need to see an actual medical doctor who specializes in this.
Usually this would be under Sports Medicine or orthopedic medicine. You can also find doctors who specialize as knee surgeons. Any of those 3 specializations will work fine. Your family doctor can also do some basic tests, x-rays, and so forth, before referring you to a specialist. Ask your parents to set up an appointment as soon as possible.
Don't be scared. Worst thing that will happen is you find out what is going on and how it can be treated. You get to decide what to do after that.
Back to Taekwondo... After treatment, you'll be able to test your limits at home, practicing your kicks and such. And you can return to class and see how it goes. You'll know after that whether or not you can really keep on doing TKD or not. If you find that you're still feeling pain in TKD, my recommendation is to find another martial art to do, or find another sport or physical activity to do. It's not the end of the world, and you'll probably be just as into whatever you decide to do.
Hope that helps.