Where. The most important indicator in helping you with this would be where you are having pain. Is it on the outer (lateral), inside (medial), front (anterior) or back (posterior) of the ankle. Or, is the feeling of pain deep in the joint itself. There are multiple structures that we evaluate with ankle pain and more information is needed.
Back of ankle. If the pain is in the back of the ankle then it could be a tendon there causing pain. There are also other tendons around the ankle that can cause pain. Have it checked out by a physician.
Ankle pain. It could be joint or arthritis, tendonitis. Need examination to be sure. There are so many possible causes without examination it's difficult to answer.