By knuckles I am considering a cracking or popping sound it makes in movement. It is known as crepitus and which is quite common due to friction.
If there is no pain, then you should not worry.
It could be because of repetitive movement of joints.
Next Steps
crepitus is an early indication of arthritis. If any of your parents have arthritis, then get your self checked as there is a probability then you may also have it.