Os peroneum syndrome; a term coined by Sobel M et al is a cause of plantar lateral foot pain. 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.
Suggestion for clinical diagnosis:
Clinical diagnosis of the painful Os peroneum syndrome can be facilitated by localization of tenderness along the distal course of the peroneus longus tendon at the cuboid tunnel by the following two tests.
1. Single stance heel rise and varus inversion stress test
2. Resisted plantarflexion of the first ray