Issue link: https://www.massageandbodyworkdigital.com/i/72103
WORKING WITH ANKLE MOBILITY, PART 2 For us bipeds, upright movement demands a delicate balance of joint mobility and stability. Ankles provide both. Their mobility allows us to walk, run, jump, skip, and hop; and their inherent stability supports and balances the considerable weight of the rest of the body through all the movements the ankles allow. The bones of the ankles have the qualities of mobility and stability built in. The solidly built tibia transmits the body's weight to the talus, the uppermost bone of the foot (Image 1). The smaller fibula rides alongside the tibia like an outrigger, providing an added dimension of stability by wrapping around the talus in a fork- like mortise-and-tenon joint—except that unlike a cabinetmaker's hardwood mortise, this living joint walks, runs, dances, skateboards, stands on tiptoe, plays tennis, etc. It is the talus' unique shape that allows the ankle's solidity and mobility to coexist. Examining the talus, we see that its upper articular surface (the trochlea or tibial plafond) is slightly wedge-shaped (Image 2). This wedge is the tenon that fits inside the mortise formed by the distal ends of the tibia and fibula. The talus (orange) has a superior articular surface (darker orange) which is 5–6 millimeters wider anteriorly, giving it a wedged shape. The widest part of the wedge moves between the tibia and fibula in dorsiflexion. Source image courtesy Primal Pictures. Used with permission. The narrowest part of the wedge is the posterior plafond1 —the portion that lies between the tibia and fibula in plantarflexion. This narrowness gives the articulation more play and mobility in plantarflexion, allowing the foot to adapt to uneven surfaces when landing with the midfoot.2 Conversely, in dorsiflexion, the widest part of the wedge-shaped talus completely fills the gap between the tibia and fibula, snugging up the ankle joint and giving boney solidity to the push-off phase, when stability is most needed. Even when completely dorsiflexed, this form-closed joint is not rigid—at least ideally. In normal function, the connective tissues joining tibia and fibula actually allow some springiness between these two bones, creating When adaptability between the tibia and fibula is lost, the widest part of the talus gets squeezed during dorsiflexion. Image courtesy Eric Franklin, originator of the Franklin Method (www.franklinmethod.com). Used with permission. earn CE hours at your convenience: abmp's online education center, www.abmp.com 111