Final answer:
The close-packed position of the midtarsal joint occurs when the foot is fully plantarflexed, which causes its ligaments to be taut, providing stability to the joint.
Step-by-step explanation:
The midtarsal joint, also known as the Chopart's joint, is the articulation between the hindfoot and the midfoot, involving the talonavicular and calcaneocuboid joints. The close-packed position of the midtarsal joint is achieved when the foot is fully plantarflexed. In this position, the ligaments of the foot are taut, adding to the joint's stability. The midtarsal joint enables important movements such as eversion and inversion of the foot, which are essential for adapting to uneven ground and participating in activities that involve side-to-side movements.