my knees hurt when i play basketball?

Go see a doctor asap. Talk to an orthopaedic doctor. Knee injuries are very common when playing sports. If your knees hurt a lot you need to see a doctor before it gets worse because it will get worse. To relieve the pain, put hot packs on it (if it's not swollen) if it gets swollen put ice packs because hot packs will make it more swollen. Wear a knee brace too! good luck!

Maybe you need to look into the shoes you have. Make sure they are really good ones for the stress your putting on your knees.

if you put your hand on it and press down on it a little and you feel it crackling inside without bending your knee it is probably spained

if it just tightins up and is hard to bend its cramping

get a knee brace that has velcro straps

maybe you tore something in your knee, that happened to me once