The demands placed on the foot and toes require a delicate balance between the need to provide a rigid platform and the ability to remold itself to adapt to uneven terrain. The foot acts as a rigid lever during the preswing phase of gait and as a shock absorber during the initial contact and loading response phases (Fig. 8-1). When running, the foot is required to absorb and dissipate about three times the person's body weight.1
Phases of gait for the right foot as defined by the Los Ranchos Medical Center system of gait analysis. This system, described in Chapter 7, divides the gait into weight-bearing and non–weight-bearing phases
Biomechanically, the functions of the foot, toes, and ankle are highly interrelated, as is the examination of these areas. This chapter describes the diagnostic techniques for the foot and toes. Chapter 9 covers the examination of the ankle and leg. Additionally, impairments and biomechanical abnormalities proximal to the foot and ankle may also influence the mechanics of the foot, a concept known as regional interdependence.2 An examination of the foot and toes should also include the trunk, hip, and knee. The functional assessment frequently includes a gait analysis, described in Chapter 7.
The foot relies on intimate and precise relationships with the various surrounding structures. True one-on-one articulation between its bones is rare, tending to be limited to the joints of the toes. The majority of the remaining bones have multiple articulations with their contiguous structures. The muscles originating off the bones of the foot (intrinsic muscles) and the extrinsic muscles originating from the lower leg provide motion and support.
Formed by 26 structural bones, the foot has three regions: the rearfoot, the midfoot, and the forefoot (Fig. 8-2). The tarsals consist of the calcaneus, talus, navicular, cuboid, and three cuneiforms. Articulating with the distal tarsals, each of the five metatarsals (MTs) leads to the proximal phalanges. Each toe consists of three phalanges (proximal, middle, and distal), with the exception of the great toe, which has only two bones (proximal and distal). Two sesamoid bones are found in the flexor hallucis brevis tendon beneath the first metatarsophalangeal (MTP) joint.
Anatomical zones of the foot. The talus and calcaneus form the rearfoot; the 3 cuneiforms, the navicular, and the cuboid form the midfoot; and the 5 metatarsals, 14 phalanges, and 2 sesamoid bones form the forefoot.
The rearfoot, formed by the calcaneus and talus, provides stability and shock absorption during the early stance phase of gait and ...