Recently, the traditional classification of Adult Acquired Flatfoot Deformity (AAFD) based on Posterior Tibial Tendon Dysfunction (PTTD) has been questioned. The expert consensus published in 2020 proposed a new classification and recommended that the designation Progressive Collapsing Foot Deformity (PCFD) be used instead of the previous PTTD. The new classification system classifies PCFD based on flexibility, location and type of deformity, which can more comprehensively elucidate the status of such deformity. This paper will interpret the new classification consensus.