The transparent circle represents the position of the subtalar joint (20) when the foot is supinated, pronated and in a neutral position (e.g., joint congruity). This position is approximately one finger width below and proximal to the medial malleolus.
Using a microwedge to measure the Primus Metatarsus Supinatus value in the PreClinical Clubfoot Deformity (readings are in millimeters).The inter and intra-rater reliability of this measuring technique has been tested and confirmed in a double blind study (Cummings, 1997).
PMSv 30-59 mm is pathognomic of the PreClinical Clubfoot Deformity (See Interpreting PMSv)
Reference:
Prof/Dr Brian A Rothbart