If you're noticing stiffness and pain in one knee, you may worry that, at some point, your other knee will develop the same symptoms. Arthritis doesn't work that way. You may develop arthritis in only one knee. The development of joint degradation in the opposite leg can be avoided by acting quickly on arthritis you have already developed. Talk to your doctor about the various conservative ways that you can slow down the breakdown of cartilage in your joints and how you can take optimal care of both of your knees at once.