An implant for replacing a portion of an articulation surface of a joint, the implant comprising: a main portion configured for inserting into a joint, wherein the main portion comprises: a porous material portion having a first bone-engaging surface; and a hydrogel portion that is bonded to the porous material portion and forming an articulation surface opposite from the first bone-engaging surface; and a bone plate portion configured for securing the implant to a bone that forms the joint; wherein the main portion has a leading end and a trailing end, wherein the leading end is configured for being inserted into the joint, and wherein the bone plate portion extends from the trailing end; wherein the bone plate portion comprises a solid metal portion that forms all exterior surfaces of the bone plate portion except for the second bone-engaging surface; and wherein the bone plate portion has at least one screw hole for receiving a bone screw; characterized in that the porous material portion has an extension piece that extends from the first bone-engaging surface and forms a second bone-engaging surface that is also formed of the porous material and extends from the first bone-engaging surface in a direction opposite from the articulation surface at an angle (Θ) with respect to the first bone-engaging surface, whereby a space is formed between the porous material portion and the extension piece at the trailing end; and in that the solid metal portion fills the space. a main portion configured for inserting into a joint, wherein the main portion comprises: a porous material portion having a first bone-engaging surface; and a hydrogel portion that is bonded to the porous material portion and forming an articulation surface opposite from the first bone-engaging surface; and a porous material portion having a first bone-engaging surface; and a hydrogel portion that is bonded to the porous material portion and forming an articulation surface opposite from the first bone-engaging surface; and a bone plate portion configured for securing the implant to a bone that forms the joint; wherein the main portion has a leading end and a trailing end, wherein the leading end is configured for being inserted into the joint, and wherein the bone plate portion extends from the trailing end; wherein the bone plate portion comprises a solid metal portion that forms all exterior surfaces of the bone plate portion except for the second bone-engaging surface; and wherein the bone plate portion has at least one screw hole for receiving a bone screw; characterized in that the porous material portion has an extension piece that extends from the first bone-engaging surface and forms a second bone-engaging surface that is also formed of the porous material and extends from the first bone-engaging surface in a direction opposite from the articulation surface at an angle (Θ) with respect to the first bone-engaging surface, whereby a space is formed between the porous material portion and the extension piece at the trailing end; and in that the solid metal portion fills the space. wherein the main portion has a leading end and a trailing end, wherein the leading end is configured for being inserted into the joint, and wherein the bone plate portion extends from the trailing end; wherein the bone plate portion comprises a solid metal portion that forms all exterior surfaces of the bone plate portion except for the second bone-engaging surface; and wherein the bone plate portion has at least one screw hole for receiving a bone screw; characterized in that the porous material portion has an extension piece that extends from the first bone-engaging surface and forms a second bone-engaging surface that is also formed of the porous material and extends from the first bone-engaging surface in a direction opposite from the articulation surface at an angle (Θ) with respect to the first bone-engaging surface, whereby a space is formed between the porous material portion and the extension piece at the trailing end; and in that the solid metal portion fills the space.