What is Foot Pronation

During the early phase of strain upon the foot, the muscles acting across the foot attempt to allay the strain upon the ligaments. They may react to this stress with pain. The posterior tibial tendon, as the prime invertor of the foot, opposes the eversion of the foot, and its tendon may become inflamed and tender. On examination, tenderness of the posterior tibial tendon can be elicited by palpation along its course under and behind the medial malleolus. The long flexor of the big toe, which has a function similar to the posterior tibial and also presses the toe to the ground, also becomes strained and painfully inflamed.

As the foot and forefoot go more into pronation, the lateral evertors must shorten to take up the slack. The peronei muscles and toe extensors, the evertors, go into “spasm” as they undergo adaptive shortening, and they too become painful and tender.

The interosseous talocalcaneal ligament which binds the talus to the calcaneus is normally taut when the foot is supinated and slack when the foot is pronated. As the strained foot pronates, the tarsal canal deforms and the talocalcaneal joint becomes abnormally mobile. Although slack, the interosseous ligament undergoes strain with ultimate inflammation. This tender ligament can be palpated at the lateral orifice of the sinus canal just anterior to the lateral malleolus. Tenderness of this ligament occurs late in the sequence as the foot undergoes pronation deformity.

Early ligamentous symptoms are felt on the plantar surface of the foot with the areas of tenderness palpable in the plantar fascia, the medial ligaments of the ankle at their attachment to the sustentaculum talus, and the posterior tibial tendon passing under the medial malleolus.

The early signs and symptoms in the soft tissues that relate to structural surface anatomy are pointed to by the patient and ascertained by the examiner. Functional anatomy gives a mechanical explanation by which abnormal function results in pain and disability. It is evident that pronation is a major cause of pain, and that deconditioning as well as excessive stress initiates a process of decompensation. This emphasizes the need for a long-range program of treatment for children with markedly pronated feet to allay ultimate pain and disability in adulthood.

The toe flexors, as well as the supinators of the foot, play a vital role in the maintenance of the longitudinal and transverse arches. Balance between the toe flexors and extensors must exist for proper foot function. Normally, the extensor digitorum longus and the lumbricals extend the distal interphalangeal joints and the toe flexors press the straightened toes against the floor. This action elevates the transverse arch. If the intrinsics are weak, the phalanges are permitted to flex, and the action of the toe flexors causes a “claw” position of the toes. The metatarsal heads become more prominent and weight-bearing. With weakness of the toe flexors, the downward pressure upon tee floor is also weakened.

The excessive joint "play” resulting from ligamentous laxity causes pain due to articular strain. The calcaneocuboid are the talonavicular joints sustain this stress primarily by virtue of the foot pronating and the forefoot everting.

Pain originating from articular strain does not subside with rest as does pain from ligamentous, tendinous, or muscular origin, No “trigger” areas are palpable, and the patient points to a region overlying the joint involved. Pain can be reproduced by forcefully everting the forefoot while immobilizing the heel.

Talonavicular arthrosis resulting from chronic foot strain causes tenderness over the dorsum of the foot at the talon avicular joint, and because the navicular is depressed in the pronated foot, there is also tenderness on the plantar surface of the foot at the calcaneonavicular ligament.