Injury of the tibialis posterior tendon: a cause of acquired valgus foot in childhood.

Accidental division of the tibialis posterior tendon near the medial malleolus is easily overlooked and can, if left untreated, cause a painful planovalgus deformity of the foot. Two such patients are described, who had small wounds near the medial malleolus and in whom the tendon's damage was not initially diagnosed. Both patients came later with a painful valgus flat foot. Diagnosis of the lesion may be difficult because the inversion and supination action of the tibialis posterior tendon can be mimicked by the long flexor tendons of the toes. A patient with an intact tibialis posterior tendon can invert and supinate the foot and then plantarflex and dorsiflex the toes with the foot held in that position. Damage to the tendon should be suspected in all penetrating wounds near the medical malleolus.