The medial malleolus is the end of the Tibia. This is the large long bone in the lower leg and the main ‘weight bearing’ bone. The tibia doesn’t extend as far down the ankle as the fibula (lateral malleolus), but rather it ‘sits’ more on top of the ankle. This is why the lateral malleolus has to glide out of the way as the ankle moves, especially during dorsi-flexion, to allow the talus to slide/glide under the tibia.
This means that the medial malleolus doesn’t move anywhere near as much to allow this gliding of the talus. It’s the fibula that moves to create the room for the dorsi flexion. This is why the mulligan/banded distraction works so well, as it essentially pulls the tibia over the talus and forces that movement (which is a classic physical therapy manipulation done passively as they drive the talus down and back under the tibia)
Interestingly enough, manipulation of the fibula head can also help the range at the ankle. If you’re an MWod Pro user then you’ll see a manipulation in this video:
I have around 8 degrees more dorsi-flexion in my left ankle than my right. This is because I have more of a ‘bony block’ in my right caused by stiffness in my tarsals and lateral malleolus. Again, this is a mob that is done by many physical therapists to help improve ankle function.
Hope that’s all made sense.