Avulsions may occur and some authors have surmised that nonunion of these avulsions may be the source of os fibulare. (10) Calcaneofibular ligament tears are second to those of the ATFL and most commonly occur in combination with ATFL injuries; they are rarely seen as isolated injuries.
(10.) Berg EE: The symptomatic os fibulare. J Bone Joint Surg 73A:1251-1254, 1991.