Table 1.

Prevalence, clinical significance, and differential diagnosis of the most common types of variants and accessory ossicles in the midfoot

Ossicle		Prevalence			Clinical significance	Differential diagnosis
Accessory navicular		4–21%	I	~ 30%	Asymptomatic	–
			II	50% bilateral 50–90%	Disruption of the synchondrosis Chronic tendinosis or tear Flat-foot deformity Osteonecrosis	Avulsion fractures of the tuberosity
			III	~ 30%	Irritation of the surrounding tissues Adventitial bursa formation Flat foot deformity	–
Os supranaviculare		1%			Asymptomatic	Avulsion fractures of the capsule of the talonavicular joint
Os peroneum		3–26% (ossified form) multipartite – 30% bilateral – 60%			Painful os peroneum syndrome Peroneus longus tear	Fracture (os trigonum—os subfibulare if migrated, multipartite if not)
Rare	Bipartite medial cuneiform	0.3–2.4%			Degeneration and overuse syndromes	Fracture
	Os cuboideum secundarium	–			Asymptomatic	Potential to mimic a mass on MR
	Os intercuneiforme	0.026%			Asymptomatic	Fracture