The MEDIAL collateral ligament of the stifle is tested by placing the stifle in extension and then applying pressure to the LATERAL aspect of the joint.
I usually place one hand on the distal femur and the other on the proximal tibia and my thumbs meet on the lateral aspect of the stifle joint. I apply pressure to the joint with my thumbs, effectively trying to “crack open” the medial side of the joint. This can only be accomplished if the stifle 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 stifle.
