The medial malleolus is an anatomical region of the tibia bone, which is the larger of the two lower leg bones. You can feel this area as the bump on the inner side of your ankle joint. It bears 90% of the weight-bearing load, so this is a common fracture. Medial malleolar fractures involve the articular surface of the ankle joint, which is where the bones meet in the joint.
Source: Verywell Health