SUSTENTACULUM TALI:- Medial surface of calcaneum bone is concave from above downwards. The concavity is attenuated by the presence of a shelf like projection of bone, called the sustentaculum tali. The groove on the lower surface of sustentaculum tali is occupied by tendon of FHL. Medial margin is related to tendon of flexor digitorum longus. Attachments:-1. Spring ligament.2. Tibialis posterior 3. Superficial fibres of deltoid ligament.4. Medial talocalcanean ligament. Origin to medial head of flexor digitorum accessorius. {Reference: BDC 6E pg no.33}