Symptomatic Accessory Ossicles of the Foot and Ankle

Accessory ossicles are small noncalcified, calcified or ossified structures found throughout the body, often noted as incidental findings. Specifically in the foot and ankle, there are at least 24 different ossicles described the majority of which are incidental. However, there are accessory ossicles that can be symptomatic, leading to significant pain and discomfort. While many of the symptomatic ossicles have been described in the literature, there are several that are under-recognized or under-reported for example, os interphalangeus and os calcaneus secundarius syndromes. This manuscript will review common and uncommon accessory ossicles including painful os peroneum, os naviculare, os calcaneus secundarius, os trigonum and os interphalangeus syndromes as well as medial sesamoiditis, with attention to the clinical and imaging findings and with an outline of the current management.