I know this dude who has ankle arthritis. What is that?

Painful ankle. Many causes of arthritis in ankle or any joint. Can be the result of wear and tear, njury or various diseases. The treatment depends on the cause and the severity of symptoms.
The Dude. If the dude in question has ankle arthritis, it is loss of cartilage, usually accompanied by bone spurring. If the joint is painful, stiff, and swollen for long periods of time, it is usually a result of arthritis. It can be caused by normal wear and tear (just like arthritis in the knee or hip). The leading cause of arthritis in the ankle is previous trauma.
Loss of cartilage. Arthritis is loss of articular (joint) cartilage and the inflammation that accompanies it.