Motion of the Foot: Joints, Muscles, and Sensorimotor Control

Abstract

1. Kinematic studies show that many joints in the foot move during the stance phase of gait in multiple planes. Some joints move more than previously recognized: The talonavicular joint and the calcaneocuboid joints move more than the subtalar joint. The midfoot joints contribute more sagittal plane motion than the ankle. The medial column moves more than the ankle. The lateral metatarsals move more than the medial metatarsals. The navicular-cuneiform joints move more than the midtarsal joint. The ankle is not a pure mitered hinge joint. It moves in the transverse and frontal planes. There is more frontal plane motion in the ankle than the subtalar joint. 2. The torque-producing capacity of a muscle is dependent upon cross-sectional area and moment arm. 3. Moment arms for the lower extremity muscles change as foot position changes. 4. The tibialis posterior has a longer moment arm for transverse plane adduction of the foot than for inversion of the foot. 5. The plantar intrinsic muscles along with the plantar aponeurosis and the plantar ligaments store and release elastic energy in response to deformation of the longitudinal arch of the foot. 6. Healthy feet display considerable compliance and variability of motion across multiple joints. There is no distinct pattern of motion which defines a “normal” foot. 7. The sensorimotor system has ultimate control over motion of the skeletal segments of the lower extremity during ambulation. The timing of muscular contraction, the force of contraction, the activation of antagonist muscles, and the pre-activation of muscles, all of which contribute to stiffness across joints creates multiple options for wide variation among the general population.