My knees are killing me why?

Many possibilities: You should seek out a physician especially if the symptoms persist or are associated with other symptoms such as fever. Have you done excessive or unusual activity recently which may have precipitated the pain?

Many possibilities: Knee pain can be due to many things such as gout, infection, inflammation of the bursa, or due to tendon, cartilage, or bone abnormalities. Have it evaluated by a professional and get the appropriate treatment.

Knee pain: There is simply not adequate info to tell you why. History, examination and possibly radiographic studies are required to give you an accurate reason.