The grinding sound, also called crackling, rubbing, snapping, etc, is what is called benign crepitus. The actual cause of this type of crepitus in the knee is not known. It is sort of like the sound made when you crack you knuckles. Yes, there is a sound, but it does not cause any problems.
Many people have crepitus in their knees. It can range from so loud that other people can hear it, to so soft it can actually only be "heard" by placing the hand on the knee and feeling for it. There is no correlation between sound and pain in the knee.
The only reason to have a total knee arthroplasty done, is for pain severe enough to interfere with daily activities, that cannot be controlled by any other means. So, if you have severe knee pain, which keeps you from doing things that you need to do each day, and you can't control the pain with medication, therapy, use of a cane, etc. then, you might want to speak with a total joint surgeon.