Final answer:
The plantar calcaneonavicular ligament, also known as the spring ligament, connects the calcaneus to the navicular bone and supports the foot's arch.
Step-by-step explanation:
The plantar calcaneonavicular ligament is also called the spring ligament. It is an important ligament that is located on the medial side of the foot and supports the arch of the foot. It connects the calcaneus (heel bone) to the navicular bone, which is key in maintaining the medial longitudinal arch of the foot. This ligament aids in supporting the head of the talus and is thus crucial for proper foot mechanics during movements such as plantar flexion.