Sprained ankle

A year ago, I sprained my right ankle and had to use an air cast for a few weeks.  It subsided and got better.  I hadn't felt any pain until recently.  Now I feel the same pain, but maybe not as severe around the whole ankle.  Discomfort along the outer ankle bone and tendon pain in the front and back of the ankle.  Could there be an underlying problem here from walking a lot during the summer.  To mention, I have had a partial knee replacement on both knees and felt pain in the back of the right knee, but that is gone now.  Therefore, my problem is my right ankle now and right knee is now fine.