There are many factors that causes knee pain. From your message,
I can't deduce what is wrong as there are no symtoms mentioned.
However, to relieve your pain in your knees, you can try using a
hotpack and apply it on your painful knee for 10 mins a few times a
day. If there is a swelling, apply coldpack instead of hotpack for
10 mins a few times a day. Note, 10 mins per application is the
optimal time. Applying more than 10 mins may be detrimental to your
knee.