Arches of the Foot
The arches of the foot are formed by the tarsal and metatarsal bones. Strengthened by ligaments and tendons, the elastic properties of arches allow the foot to act as a spring, dissipating impact forces and storing energy to be transfered into the subsequent step improving locomotion.
The two longitudinal arches and a transverse arch are maintained by the interlocking shapes of the foot bones, strong ligaments, and pulling muscles during activity. The slight mobility of these arches when weight is applied to and removed from the foot makes walking and running more economical in terms of energy.
Excessive strain on the tendons and ligaments of the feet can result in fallen arches or flat feet.
Arches of the Foot
Skeleton of foot. Lateral aspect.
Arches of Foot
Skeleton of foot. Medial aspect.
Longitudinal Arches
The longitudinal arch of the foot can be broken down into several smaller arches. The main arches are the antero-posterior arches, which may, for descriptive purposes, be regarded as divisible into two types—a medial and a lateral.
Medial Arch
As can be examined in a footprint, the medial longitudinal arch curves above the ground. It is made by the calcaneus, the talus, the navicular, the three cuneiforms, and the first, second, and third metatarsals.
Its summit is at the superior articular surface of the talus. Its two extremities or piers, on which it rests in standing, are the tuberosity on the plantar surface of the calcaneus posteriorly, and the heads of the first, second, and third metatarsal bones anteriorly.
The chief characteristic of this arch is its elasticity, due to its height and to the number of small joints between its component parts. Its weakest part (i.e., the part most liable to yield from too much pressure) is the joint between the talus and navicular, but this portion is braced by the plantar calcaneonavicular ligament, also called the spring ligament, which is elastic and is thus able to quickly restore the arch to its original condition when the disturbing force is removed.
The ligament is strengthened medially by blending with the deltoid ligament of the ankle joint, and is supported inferiorly by the tendon of the tibialis posterior, which is spread out in a fan-shaped insertion and prevents undue tension of the ligament or such an amount of stretching as would permanently elongate it.
The arch is further supported by the plantar aponeurosis, by the small muscles in the sole of the foot, by the tendons of the peroneus longus and the tibialis anterior and posterior, and by the ligaments of all the articulations involved.
Lateral Arch
In contrast, the lateral longitudinal arch is very low. It is composed of the calcaneus, the cuboid, and the fourth and fifth metatarsals.
Its summit is at the talocalcaneal articulation, and its chief joint is the calcaneocuboid, which possesses a special mechanism for locking and allows only a limited movement. The most marked features of this arch are its solidity and its slight elevation.
Two strong ligaments—the long plantar and the plantar calcaneocuboid—the extensor tendons, and the short muscles of the little toe preserve its integrity.
Fundamental Longitudinal Arch
While these medial and lateral arches may be readily demonstrated as the component antero-posterior arches of the foot, the fundamental longitudinal arch is contributed to by both, and consists of the calcaneus, cuboid, third cuneiform, and third metatarsal: all the other bones of the foot may be removed without destroying this arch.
Transversal Arches
In addition to the longitudinal arches, the foot presents a series of transverse arches. The arches are complete at the posterior part of the metatarsus and the anterior part of the tarsus, but in the middle of the tarsus they present more of the characteristics of concavities.
These are directed downward and medially, so that when the medial borders of the feet are placed in apposition, a complete tarsal dome is formed. The transverse arches are strengthened by the interosseous, plantar, and dorsal ligaments; by the short muscles of the first and fifth toes (especially the transverse head of the adductor hallucis), and by the peroneus longus, whose tendon stretches between the piers of the arches.