I would not try to strengthen an injured knee if you don't even know what you have done. First off, even if you did something to the knee, a doctor would not have you doing strengthening exercises right off the bat. You must get the swelling, etc. out of the knee before you would ever do strenghthening things.

So, rest, ice, elevation, anti-inflammatories if your stomach can tolerate them, try not use as much as possible; no exercises!

Then once you know if you have injured something. You need to find out if it is serious or not. If it is really requires surgery, then you have the surgery. And, then any exercises to strengthen would be done well after surgery.

If no surgery is necessary and it is just a minor injury, once the inflammation, etc. is gone, you could slowly begin strengthening exercises which probably should be supervised by a PT or some such professional.

spoke