Shelby, it may be spondylolisthesis which is basically a vertebrae slipping around, probably in the lower back but possibly the knees (which affects your lower back). It's fairly common, affecting about 1 in 20 people. The reason why you hear it in your ears is because bones are very good at carrying sound internally through vibrations, and we have tiny little bones in our ears that pick up those vibrations. In young people, it is usually caused by a stress injury from anything like sports, falling down, or even wearing high heels too much. In aged people, it can be from a degenerative bone disease like osteoarthritis.
If this is not causing you serious pain or disability, you probably don't need treatment (which can be worse than the disease). I would advise to avoid anything that might further injure your knees or back like heavy lifting, bike riding (if you exercise, switch to an elliptical machine), and NO HIGH HEELS. A great way to alleviate minor lower back pain is to stretch your hamstrings (the muscle in the back of your thighs) by starting from a standing position and bending at the hips, reaching as far to the ground as you can.
I hope this helps, but if you are still concerned, your physician and/or chiropractor can go over possible treatments with you.