When is an ankle in open pack?

• A. Plantarflexed
• B. Dorsiflexed
• C. Neutral
• D. Slight plantarflexion with inversion

Answer: (A)

Open packed (loose-packed) means the joint capsule is most lax and the articular surfaces have the least contact, allowing the greatest freedom for accessory motions. For the ankle joint (the talocrural joint), this occurs in plantarflexion. In plantarflexion, the talus sits less snugly between the tibia and fibula, the ligaments are relatively slack, and the joint is easier to distract or glide—which is why many exam and manual therapy guidelines use this position for open-pack access. By contrast, dorsiflexion wedges the wider part of the talus into the mortise, tightening the ligaments and achieving the closed-pack state. Neutral is a mid-range position and not the loose-packed state, and adding inversion with slight plantarflexion isn’t necessary for the loose-pack position. Therefore, plantarflexion is the open-pack position for the ankle.