Calcaneal apophysitis also known as Sever disease is mostly seen in physically active children. It is usually self-limiting. 

Fragmentation of the secondary nucleus may play an important factor in the diagnosis of Sever disease, although this remains controversial in radiographic studies ¹. Children may show considerable variation in the radiographic appearance of the secondary ossification center of the calcaneus at different ages ².

One study showed that symptomatic heels of 14 children showed fragmentation of the secondary nucleus on both conventional radiographs and sonograms proving that ultrasonography may be valuable in the diagnosis of Sever disease with clinical correlation ¹.  

Another study showed that the difference in a normal cohort and apophysitis cohort was the degree of fragmentation of the secondary nucleus on conventional radiographs, which was greater in the apophysitis group ². This suggests that a mechanical etiology contributes to the condition. 

Both radiography and ultrasonography may prove valuable in the clinical diagnosis of calcaneal apophysitis also known as Sever disease, eponymously named after, an American orthopedic surgeon, James Sever in 1912 ².