I had an MRI on ankle, showed I have marked degenerative change associated wit bone marrow bruising @ medial articulation between talus and calcaneus?

Subtalar arthritis. What you are describing in a form of subtalar arthritis (the joint below your ankle that allows foot to go inward or outwards. This can be due to trauma, a fibrous coalition of the tale/heel bones or an early sign of an inflammatory arthritis like rheumatoid or psoriatic. Bracing and or injections can help, but if very severe and painful a subtler fusion is necessary.
Unusual. That is unusual for a 29 year to basically have severe arthritis on the inside of your ankle. It is probably postraumatic, ie from an injury or injuries. Don't hesitate to be seen for treatment options.