Painful Os Peroneum Syndrome: A Spectrum of Conditions Responsible for Plantar Lateral Foot Pain

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Abstract
Plantar lateral foot pain may be caused by various entities and the painful os peroneum syndrome (a term coined by the authors) should be included in the differential diagnosis. Painful os peroneum syndrome results from a spectrum of conditions that includes one or more of the following: (1) an acute os peroneum fracture or a diastasis of a multipartite os peroneum, either of which may result in a discontinuity of the peroneus longus tendon; (2) chronic (healing or healed) os peroneum fracture or diastasis of a multipartite os peroneum with callus formation, either of which results in a stenosing peroneus longus tenosynovitis; (3) attrition or partial rupture of the peroneus longus tendon, proximal or distal to the os peroneum; (4) frank rupture of the peroneus longus tendon with discontinuity proximal or distal to the os peroneum; and/or (5) the presence of a gigantic peroneal tubercle on the lateral aspect of the calcaneus which entraps the peroneus longus tendon and/or the os peroneum during tendon excursion. Familiarity with the various clinical and radiographic findings and the spectrum of conditions represented by the painful os peroneum syndrome can prevent prolonged undiagnosed plantar lateral foot pain. Clinical diagnosis of the painful os peroneum syndrome can be facilitated by the single stance heel rise and varus inversion stress test as well as by resisted plantarflexion of the first ray, which can localize tenderness along the distal course of the peroneus longus tendon at the cuboid tunnel. Radiographic diagnosis should include an oblique radiograph of the foot for visualization of the os peroneum and, if indicated, other imaging studies. Recommended treatment ranges from conservative cast immobilization to surgical approaches including: (1) excision of the os peroneum and repair of the peroneus longus tendon, and (2) excision of the os peroneum and degenerated peroneus longus tendon with tenodesis of the remaining remnant of peroneus longus to the peroneus brevis tendon.