The stability of the ankle joint is maintained by all of the following, except -
Plantar calcaneonavicular (spring) ligament
Deltoid ligament
Lateral ligament
Shape of the superior talar articular surface
Calcaneonavicular ligament or spring ligament is a powerful ligament attahced posteriorly to the calcaneum and anteriorly to the navicular bone. So it is obvious that it will not participate in the formation of ankle joint.