Which ligament specifically helps support the medial side of the ankle?

The deltoid ligament is the correct choice as it plays a crucial role in supporting the medial side of the ankle. This ligament is a strong, broad ligament that stabilizes the joint by connecting the tibia to the bones of the foot on the medial aspect, namely the talus and calcaneus. Its primary function is to prevent excessive eversion of the foot, which is crucial for maintaining stability during weight-bearing activities.

The deltoid ligament's structure enables it to resist the forces that may push the foot outward, thus providing protection against injuries that can occur from uneven surfaces or during certain athletic activities. This structural support is vital as it helps in maintaining proper foot alignment and function during movement.

The other ligaments listed, while they have important functions in ankle stability, do not provide support to the medial side. The anterior tibiofibular ligament primarily stabilizes the syndesmosis between the tibia and fibula, the calcaneofibular ligament supports the lateral aspect of the ankle, and the lateral collateral ligament complex also contributes to lateral stability. Each of these ligaments has a specific role in ankle mechanics, but none serve the medial side support function that the deltoid ligament does.