Almost everytime I bend my knees I hear a cracking noise w no pain. This has been going on for 4-5 years. I think im bow legged. What is causing this?

Crepitus. Crunching or cracking sounds in the knee is known as crepitus. This is usually due to roughness of the cartilage behind the knee cap. This roughened cartilage of the knee cap slides up and down when walking or bending causing the crepitus. See your family doctor, internist or orthopedic surgeon if you have pain.
Arthritis. You most likely have some wear of the joint surfaces of your knee. This can be called arthritis or chondromalacia. As long as you do not have pain or swelling there is nothing to do about the noise.
Sign of arthitis. Cracking noise mean the cartilage which cover the end of the bone started to have problem in it. This the firset stage of arthitis called degnertive arthitis, should be looked at and may be start some treatment.