An ankle prosthesis comprising: - a tibial component comprising a substantially plate-like tibial main body having a tibial top surface adapted to engage with one end of a tibia, and a tibial bottom surface adapted to engage with other components of said prosthesis, said tibial main body having a substantially quadrilateral profile in a top view, which is delimited by a tibial front side, a tibial rear side and a pair of tibial flanks (112, 113), said tibial top surface being curved extending from said front side to said rear side, its concavity facing towards said tibial bottom surface, and - a talar component comprising a talar main body with a talar top surface and a talar bottom surface, wherein the talar bottom surface is of quadrilateral shape and is delimited by a talar front side, a talar rear side and a first and a second talar flanks (212, 213), wherein said talar top surface is curved extending from said talar front side to said talar rear side with its concavity facing towards said talar bottom surface, wherein said talar top surface is curved extending from said first talar flank to said second talar flank with its convexity facing towards said talar bottom surface; characterised in that said tibial main body has several spikes extending from said tibial top surface without coming into contact with any one of said tibial sides or tibial flanks of said tibial main body and wherein at each talar side and at each talar flank of said quadrilateral shape, the talar main body includes an expansion extending from said talar bottom surface adapted to directly engage with a patient's talus. - a tibial component comprising a substantially plate-like tibial main body having a tibial top surface adapted to engage with one end of a tibia, and a tibial bottom surface adapted to engage with other components of said prosthesis, said tibial main body having a substantially quadrilateral profile in a top view, which is delimited by a tibial front side, a tibial rear side and a pair of tibial flanks (112, 113), said tibial top surface being curved extending from said front side to said rear side, its concavity facing towards said tibial bottom surface, and - a talar component comprising a talar main body with a talar top surface and a talar bottom surface, wherein the talar bottom surface is of quadrilateral shape and is delimited by a talar front side, a talar rear side and a first and a second talar flanks (212, 213), wherein said talar top surface is curved extending from said talar front side to said talar rear side with its concavity facing towards said talar bottom surface, wherein said talar top surface is curved extending from said first talar flank to said second talar flank with its convexity facing towards said talar bottom surface; characterised in that said tibial main body has several spikes extending from said tibial top surface without coming into contact with any one of said tibial sides or tibial flanks of said tibial main body and wherein at each talar side and at each talar flank of said quadrilateral shape, the talar main body includes an expansion extending from said talar bottom surface adapted to directly engage with a patient's talus.