Tarsal coalition occurs in approximately 1%. It typically presents in adolescence. 50% are bilateral (even if symptomatic on only one side). Frequently pes planus (flat foot) is a feature. Coalition may be bony, fibrous (this case) or cartilaginous.

The commonest coalition is calcaneonavicular. This is best seen on an oblique projection.

In a bony coalition, a ‘bony bar’ is observed. In a fibrous coalition, irregularity and narrowing of the bony interfaces with sclerosis is identified (this case). If further imaging is required, CT is the investigation of choice.

Case courtesy of: Dr Ian Bickle