The human foot is a complex structure that manages the entire body’s weight, absorbing forces and adapting to uneven terrain with every step. This capacity for balance and movement relies on a dense network of nerves that constantly transmit information to and from the brain. These pathways enable a person to sense the ground, adjust muscle tension, and execute sophisticated motor functions necessary for activities like walking and running. This continuous feedback loop governs posture and locomotion.
Primary Nerve Sources Entering the Foot
The nervous system of the foot originates from two main nerves that descend from the thigh as terminal branches of the larger sciatic nerve. The Common Peroneal nerve, also known as the Common Fibular nerve, courses around the outside of the knee before dividing into its two main branches. This nerve is responsible for much of the motor control and surface sensation on the top of the foot.
The Posterior Tibial nerve travels down the back of the leg alongside the blood vessels. It passes behind the medial malleolus (the bony prominence on the inside of the ankle) and enters the foot through the tarsal tunnel, where it immediately splits to supply the sole.
Mapping Sensory Nerves of the Foot’s Surface
The feeling of touch, temperature, and pain on the foot’s exterior is handled by nerves that are primarily sensory in function. The Superficial Peroneal nerve supplies the majority of the skin across the top, or dorsum, of the foot. It branches out to provide sensation to the skin over the toes.
The Sural nerve runs along the outer side of the ankle and provides sensory input to the lateral edge of the foot, including the fifth toe. On the opposite side, the Saphenous nerve, a branch of the femoral nerve, covers the skin over the inner ankle and the medial side of the foot’s arch. These nerves are responsible for most of the foot’s protective sensation.
The Deep Peroneal nerve, primarily responsible for motor control, also provides sensation to a small area. It sends a sensory branch to the skin covering the web space between the first and second toes. This is the only area on the dorsum of the foot not supplied by the Superficial Peroneal nerve. Mapping these specific areas is important for diagnosing nerve compression or injury.
Nerves Controlling Movement and the Sole
Beneath the surface, the Deep Peroneal nerve manages intricate motor functions. This motor nerve controls the muscles responsible for dorsiflexion, which involves lifting the foot and toes toward the shin. This movement keeps the toes from dragging while walking. Damage to this nerve results in foot drop, where a person cannot properly lift the front of their foot.
The Posterior Tibial nerve, upon entering the sole, divides into the Medial Plantar nerve and the Lateral Plantar nerve. The Medial Plantar nerve is the larger of the two and provides motor control to a group of four intrinsic foot muscles, including the muscle that flexes the great toe. For sensation, it covers the medial two-thirds of the sole and the three and a half toes closest to the big toe.
The Lateral Plantar nerve is the counterpart, supplying motor control to most of the remaining small muscles within the sole. Its sensory function covers the lateral one-third of the sole and the skin of the remaining one and a half toes. These plantar nerves are responsible for the fine motor adjustments necessary for maintaining stability and pushing off the ground.
Common Nerve-Related Foot Conditions
Tarsal Tunnel Syndrome occurs when the Posterior Tibial nerve is compressed as it passes through the narrow tunnel on the inside of the ankle. This compression leads to symptoms felt along the nerve’s distribution, often described as burning or tingling pain across the sole and arch of the foot.
Another frequent issue is Morton’s Neuroma, which involves irritation and thickening of an interdigital nerve, most commonly occurring between the third and fourth toes. The condition is characterized by sharp, shooting pain in the forefoot, often accompanied by a sensation of standing on a small pebble inside the shoe. This irritation is typically caused by compression of the nerve as it runs between the metatarsal bones.
A more generalized condition affecting the feet is peripheral neuropathy, frequently seen in people with diabetes. High blood sugar levels can damage the small blood vessels that nourish the nerves, causing them to malfunction. Because the longest nerves in the body are affected first, symptoms usually begin in the feet, presenting as numbness, tingling, or a pins-and-needles sensation. This loss of protective sensation can allow minor injuries to go unnoticed, potentially leading to severe complications.