Treatment of a Progressive Collapsing Foot Deformity Abstract. The so-called "flat foot" can be more accurately described in German as "Knick-Senkfuss" or "kinking-flatfoot". The "kink" refers to the hindfoot axis as such, which can be identified by the intersection of the longitudinal axes of the Achilles tendon and the tuber calcanei. The designation "flat foot" marks the appearance of the longitudinal axis, that is, the medial longitudinal arch, which is easy to determine clinically. Nowadays, a new terminology has been added: Progressive collapsing foot deformity (PCFD). The forms of a PCFD are manifold, as are the possible causes. For this reason, the forms of therapy to be used are often not very simple and must be carefully considered and applied. Not always are PCFD in need of treatment. That means that there are people who have always had such deformities but never develop symptoms. For this reason, only symptomatic patients suffering from a PCFD need treatment. The degree of treatment and its success depends on the careful examination and interpretation of the findings by the orthopedic surgeon. This article deals with treatment of PCFD and attempts to provide a logical overview.