A medial collateral injury to the tarsus is diagnosed by placing the tarsus in extension and then applying pressure to the LATERAL side of the tarsus.
I usually place my hands on the distal tibia and the metatarsals, with my thumbs meeting on the lateral aspect of the tarsus. I then apply pressure with my thumbs to the tarsus effectively trying to “crack open” the medial side of the tarsus. This can only be accomplished if the tarsus is placed in extension first.
If it actually does ‘crack open’ then the medial collateral ligament has been disrupted. It may be useful to compare to the contralateral limb. The lateral collateral ligament is tested in the same way but now your hands/thumbs are on the medial aspect of the tarsus.
