Alignment and joint motion in the normal foot.

Biomechanical evaluation of the foot is based on the assumption that a vertical stance position of the calf and the calcaneus in subtalar neutral (the "ideal foot") provides optimal function with minimal risk of injury. The purpose of this study was to discuss the concept of the "ideal foot" with reference to a set of normative goniometric data. One-hundred and twenty-one healthy subjects (59 men and 62 women; mean age = 35 years; range = 20-50 years) participated in a standardized clinical assessment of ankle and subtalar joint motion, subtalar neutral, forefoot alignment, calcaneal stance, and the tibia to vertical angle. All subtalar measurements were referred to the neutral position. A majority had a subtalar neutral in slight valgus (overall mean = 2 degrees), a forefoot in moderate varus (overall mean = 6 degrees), and a calcaneal stance in valgus (overall mean = 7 degrees). The mean tibia to vertical angle was 6 degrees in varus. Women had a greater range of ankle and subtalar joint motion than men but age had little influence. None of the subjects conformed to the "ideal foot," which appears to be rare and should be abandoned in favor of a reference based on clinical observation rather than on theoretical considerations.