We defined foot and ankle motion with respect to the neutral position. Thirteen normal fresh-frozen specimens of the human foot were used. The foot was placed in the extreme positions of pronation, supination, dorsiflexion, and plantar flexion, and positions of multiple bones were monitored simultaneously with a magnetic tracking device to determine rotation of the talocrural, subtalar, metatarsal-navicular, and talonavicular joints under the various conditions. In pronation, the most rotation occurred at the metatarsal-navicular level, followed by the navicular-talar, talar-tibial, and calcaneal-talar levels. In supination, most rotation occurred at the navicular-talar level, followed by the calcaneal-talar, talar-tibial, and metatarsal-navicular levels. In dorsiflexion, most rotation occurred at the talar-tibial level, followed by the navicular-talar, calcaneal-talar, and metatarsal-navicular levels. In plantar flexion, most rotation occurred at the talar-tibial level, but there was considerable motion at the navicular-talar, metatarsal-navicular, and calcaneal-talar levels. Understanding the specific joint motions that occur with various positions of the foot and ankle is important because measurements of joint mobility may assist in establishing diagnoses, monitoring clinical conditions, determining indications for operative treatment, assessing results of treatment, and following the progress of rehabilitation.
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