The　primary　objective　of　this　paper　is　to　study　the　use　of　medical　image-based　finite　element　(FE)　modelling　in　subject-specific　midsole　design　and　optimisation　for　heel　pressure　reduction　using　a　midsole　plug　under　the　calcaneus　area　(UCA).　Plugs　with　different　relative　dimensions　to　the　size　of　the　calcaneus　of　the　subject　have　been　incorporated　in　the　heel　region　of　the　midsole.　The　FE　foot　model　was　validated　by　comparing　the　numerically　predicted　plantar　pressure　with　biomechanical　tests　conducted　on　the　same　subject.　For　each　UCA　midsole　plug　design,　the　effect　of　material　properties　and　plug　thicknesses　on　the　plantar　pressure　distribution　and　peak　pressure　level　during　the　heel　strike　phase　of　normal　walking　was　systematically　studied.　The　results　showed　that　the　UCA　midsole　insert　could　effectively　modify　the　pressure　distribution,　and　its　effect　is　directly　associated　with　the　ratio　of　the　plug　dimension　to　the　size　of　the　calcaneus　bone　of　the　subject.　A　medium　hardness　plug　with　a　size　of　95%　of　the　calcaneus　has　achieved　the　best　performance　for　relieving　the　peak　pressure　in　comparison　with　the　pressure　level　for　a　solid　midsole　without　a　plug,　whereas　a　smaller　plug　with　a　size　of　65%　of　the　calcaneus　insert　with　a　very　soft　material　showed　minimum　beneficial　effect　for　the　pressure　relief.