Recently, the traditional classification of adult acquired flatfoot deformity (AAFD) based on posterior tibial tendon dysfunc-tion (PTTD) has been questioned. The expert consensus published in 2020 proposed a new classification and recommended that the progres-sive collapsing foot deformity (PCFD) be used instead of the previous PTTD. The new classification system classifies PCFD based on flexibili-ty, location and type of deformity, which can more comprehensively elucidate the status of such deformity. This paper will interpret the newclassification consensus.