The calcaneonavicular bar locates to the anterolateral aspect of the foot in the region of the sinus tarsi. Pes planus and heel valgus may b e present. A misnomer of peroneal spastic flatfoot has been used to describe the flat foot associated with tarsal coalitions. True muscle spasm is not present according to EMG studies. Rather, the peroneal muscles are shortened and attempted foot inversion causes pain b y stretching these muscles.
Subtalar motion is decreased.
The ankle joint may have increased laxity and give the false impression of greater subtalar motion. Radiographs - AP, lateral, oblique at 45 degrees, and Harris view. A coalition may be difficult to pick up on the AP and lateral views due to the overlap of bones but there may be some subtle clues. Beaking of the talus or narrowing of the subtalar joint may be present. Harris view may be helpful to evaluate the subtalar joint but a CT is often obtained to rule out subtalar coalition.