The Human Foot
"The human foot is a masterpiece of engineering and a work of art."
~ Leonardo da Vinci
The foot is one of the most fascinating parts of the body. Three of the most interesting things about your feet are the arches in each foot. Arches are shock absorbers and springs. Yes! You literally have a spring in your step! And arches are 100% unique to humans.
There are 56 bones in your feet - fully 25% of all the bones in your body are beneath your ankles. There are 30 muscles that operate your foot; ten extrinsic muscles found in the leg and 20 intrinsic muscles found in the foot itself. Watch the video to explore a dissection of the human foot.
The foot is divided into three regions: the forefoot (which includes the phalanges and metatarsals), the midfoot (includes the cuboid, navicular, and cuneiform bones), and the hindfoot (the calcaneus and talus bones). All three regions (depicted in Figure 1) participate in the formation and function of the foot arches. The many bones (and joints between them) allow significant amount of subtle movement in the foot. The most extensive movement in the foot happens between the first metatarsal and proximal phalanx of the big toe. This joint is called the first metatarsophalangeal joint (MTP). The range-of-motion (ROM) for this joint is about 40 degrees of flexion and up to 90 degrees of extension. The plantar fascia extends from the heel to the toes and, most importantly, crosses the first MTP joint. This joint and the plantar fascia play a crucial role in foot biomechanics, as described below.
The Windlass Mechanism
One of the neatest things about foot biomechanics is the windlass mechanism. A windlass is a type of lever system. It is most famously used in old water wells and sometimes to lift heavy boat anchors. The device consists of a rope that is wound around a spool using a crank (Figure 2).The plantar fascia serves as the rope, the first MTP joint serves as the spool, and the calf muscles serve as the crank. When you walk, your foot alternates between a supple landing platform that can accommodate various terrain to a stiff propulsion rod that can lift your entire body weight. The supple landing foot occurs because the windlass mechanism is disengaged when you step down and the bones of the foot are loose and movable. The rigid propulsion foot is created when the windlass is engaged by winding the plantar fascia around the first MTP joint. This puts tension on the fascia that lifts the medial longitudinal arch and shortens the foot by about 1 cm. This shortening locks the bones of the foot tightly together making the foot rigid. You should be able to see this effect on your own foot by simply flexing and extending your big toe while watching your arch.
Footwear & Feet
It is widely recognized that shoes cause harm to our feet, but most podiatrists are still unlikely to suggest ditching your shoes. Hallux valgus, bunions, corns, ingrown toenails, toenail fungus, athlete's foot, fallen arches, Morton's neuroma, and plantar fasciistis are just some of the foot ailments created by shoes. Although going barefoot is largely safe, it does also come with risks, but the health benefits of walking barefoot far out way those risks for healthy people in most (civilized) environments.
The main problem with footwear is that shoes are designed for fashion not function. The vast majority of shoes on the market are horrible for your feet. They reshape the foot over time to change both the anatomy of the foot and the biomechanics of walking (Figure 4).
Most damage done to our feet by shoes is permanent. The big exception to this rule may be fallen arches. If you have flat feet, which about 25% of the population does due to footwear, then walking barefoot may strengthen and raise your arches according to studies performed by several researchers. In my own study, I followed the arch height of a volunteer for several years after he ditched his shoes and adopted a mostly barefoot lifestyle. This individual's arches went from obviously low to higher than average (Figure 5).
Walking barefoot might be the single best thing you can do for the health of your feet (and knees and hips and back). So kick off your shoes and take a barefoot stroll.