This chapter provides detail description of Pes Planus Deformity. Chapter has 15 well illustrated diagrams and pictures. Flat foot deformity, stages of posterior tibial tendon dysfunction, tenosynovitis without deformity, ruptured tibial tendon and flexible pes planus, rigid hindfoot vulgus, ankle valgus, surgical treatment of pes planus deformity, triple arthrodesis, deltoid ligament reconstruction are described in detail covering etiopathogenesis, clinical presentation, diagnosis and management. 1 table is included to highlight clinical staging of posterior tibial tendon dysfunction. One flow chart is added to depict minimal invasive deltoid ligament reconstruction. 18 references are included at the end of the chapter to facilitate further reading.