Why does my knee make a grinding noise when i walk?

Possible arthritis : This may be due to osteoarthritis. In osteoarthritis a term call 'crepitus' often occurs. This is a noise that is due to the friction of bone. It is often due to arthritis and other causes are also possible . I would recommend you see your PCP and have them perform a physical exam where they can diagnose you. If it is arthritis weight loss and physical therapy can often help. Take care.