The medial plantar nerve runs through the inner arch of each foot, providing sensation and allowing movement of certain joints and muscles. This nerve runs alongside the medial plantar artery, which supplies blood flow to three-and-a half toes, starting with the big toe on each foot. The medial plantar nerve originates in the lower back as the sciatic nerve before it branches off to run down the buttocks and alongside the large tibia bone in the thigh. It then crosses the inside part of the ankle to the heel of the foot. From the heel, smaller nerve endings travel to toes on the inside, or medial, part of each foot.
Three major muscles in the arch of the foot are controlled by the medial plantar nerve, along with skin on the sole of the foot. The abductor hallucis regulates flexing of the big toe and provides arch support. The flexor digitorum brevis represents a muscle in the center of the arch, which controls movement of four toes and also supports the arch. Both of these muscles exist in the first of three muscular layers in the foot.
In the third layer of muscle, the medial plantar nerve branches to the flexor hallucis brevis. This muscle permits flexing the big toe at the joint near the base of the digit. The lateral plantar nerve, on the outer part of the arch, controls muscles used to move and flex one-and-a-half toes on the outside of the foot. An artery adjacent to this nerve sends blood supply to these digits.
A condition affecting the medial plantar nerve known as medial plantar neuropraxia might affect athletes who participate in long-distance running or endurance sports. If the nerve becomes compressed in an adjacent tunnel-like structure, it could cause swelling and pain. Runners with flat feet are more prone to problems with this nerve because poor arch support might damage the nerve when the foot hits the ground.
If the nerve gets pinched, it might cause chronic pain at the inner part of the arch. A burning sensation in the heel of the foot might also occur when the plantar nerve becomes trapped or damaged. If tenderness occurs when the arch is palpated, it might indicate problems with the nerve. Some doctors x-ray bones of the foot that support the arch to diagnose medial plantar neuropraxia. Injections of anesthetics might also be used to see if pain disappears.
Athletes suffering from the condition might be advised to rest to prevent further irritation of the nerve. Physical therapists typically recommend additional arch support in running shoes or using a different type of shoe in training and competition. Therapists might also work with runners to revise their gaits to relieve pressure on the plantar nerve. Cortisone injections might also help, along with surgery to alter the position of ligaments, giving the nerve more room.