My wife has leg pain around het knee an headaches an her eye hurts all on the same side. What could it be? Please help

It is possible she. Some problem called multiple sclorsis were this kind symptoms could be present, take her to docotr to check it out. Good luck.
See a doctor. Your description does not fit any specific diagnosis. The knee pain may or may not be related to the headache and eye pain. Headache and eye pain may be signs of serious eye disease so go see an eye doctor.