The talar declination angle is used to assess the longitudinal arch height including in Charcot foot.
Measurement
The talar declination angle is drawn on the weight-bearing lateral foot radiograph between the mid-talar axis and the supporting surface.
Interpretation
It should usually measure ~21°.
If the first metatarsal axis is steep, the mid-talar axis approaches the horizontal and is projected above the first metatarsal. This indicates that the longitudinal arch is relatively high and there is pes cavus.
Conversely, where there is pes planus and a low arch, the first metatarsal axis is flattened and the mid-talar angle increases such that the mid-talar axis passes inferior to the first metatarsal.