FOOT MOTION BACK PAIN

HOW ABNORMAL FOOT MOTION CAN BE A MAJOR CONTRIBUTOR TO LOWER BACK AND PELVIC PROBLEMS

OF ENGINEERING AND A WORK OF ART (Leonardo da Vinci)

BY NICK DINSDALE, BSc

INTRODUCTION The foot combines mechanical complexity and structural strength. The human foot makes up an eighth (26 bones) of all the bones in the body, more than 30 joints, and 10 major extrinsic muscle tendons. These musculoskeletal structures work together with the neurovascular elements to provide support, balance and locomotion during gait. The foot has three very demanding roles: 1) it must be a loose adaptor to accommodate uneven terrain 2) it must be able to absorb shock on impact

3) it has to form a rigid lever during push-off (1). If the foot fails to function correctly,

problems can arise anywhere along the kinetic chain and in the lower back. Both low-arched and high-arched

feet have been reported to be major factors in making an individual more prone to injury (2,3). People involved in increased levels of physical activity, such as athletes, tend to be more susceptible to gait-related injuries (2,4).

NORMAL FOOT MECHANICS DURING GAIT Pronation and supination are normal

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THE FOOT IS A MASTERPIECE

The foot contains many bones, joints and tendons that work together to enable gait. Dysfunction of any of these aspects of the foot may cause problems anywhere along the kinetic chain and in the lower back (Fig.1). This article reviews the basic anatomy of the foot and discusses some of the lower-back problems associated with abnormal foot motion.

spinal scoloiosis

abnormal pelvic tilt

imbalance of pelvic muscles

malalignment of hip

malalignment of knee internal rotation of thigh

internal rotation of leg

subtalar pronation (flat everted foot)

Figure 1: The kinetic chain - foot dysfunction predisposes the kinetic chain to abnormal repetitive stresses

movements of the foot that occur at the subtalar joint with every step. At the beginning of the gait cycle, the foot is in a supinated position. As the heel strikes the ground, the foot immediately begins to pronate: the foot rolls inwards in order to gain ground contact, the tibia rotates internally, the heel everts, the arches tend to flatten, and the mid- foot “unlocks” and becomes slightly unstable (Fig. 2). Pronation allows the foot to become a flexible mobile adaptor to absorb ground impact and accommodate uneven terrain. As the body weight moves forward over the forefoot, resupination should occur (Fig. 3). Supination converts the foot from a flexible mobile adaptor into a rigid lever in preparation for the propulsive phase of gait. The tibia starts to externally rotate, the medial arch lifts along with the navicular bone, the heel starts to invert, the first ray drops, and the peroneal longus contracts to “lock” the cuboid bone, making the foot stable and thus creating a secure platform. This is important because the other foot is now swinging forward for the next step and the pelvis must remain level and stable throughout the mid- stance phase. Once this has occurred, the heel can lift and the big toe joint extends (windlass mechanism) to

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