. An assembly for conducting arthroplasty on a knee joint, the assembly comprising: (a) a fundamental instrument configured to be secured with respect to a proximal tibia of the knee joint, and (b) an adjustment instrument configured to be coupled to the fundamental instrument, characterised in that the fundamental instrument includes a bench having a bench connector that includes a substantially planar superior surface and configured to be oriented with the substantially planar superior surface at a neutral anterior / posterior slope and a neutral varus / valgus angle relative to the proximal tibia when the fundamental instrument is secured with respect to the proximal tibia; and the adjustment instrument comprises: (i) a receiver structure configured to connect to the bench connector of the fundamental instrument and defining an alignment axis, wherein the receiver structure is further configured to permit, when the bench connector is connected to the receiver structure, an angular adjustment of the adjustment instrument relative to the fundamental instrument about an axis substantially perpendicular to the substantially planar superior surface of the bench connector, and a medial / lateral translational adjustment of the adjustment instrument relative to the fundamental instrument along the substantially planar superior surface of the bench connector; and (ii) a cutting guide connector oriented at a predetermined slope angle relative to the alignment axis of the receiver structure, the cutting guide connector configured to connect to a cutting guide. (a) a fundamental instrument configured to be secured with respect to a proximal tibia of the knee joint, and (b) an adjustment instrument configured to be coupled to the fundamental instrument, characterised in that the fundamental instrument includes a bench having a bench connector that includes a substantially planar superior surface and configured to be oriented with the substantially planar superior surface at a neutral anterior / posterior slope and a neutral varus / valgus angle relative to the proximal tibia when the fundamental instrument is secured with respect to the proximal tibia; and the adjustment instrument comprises: (i) a receiver structure configured to connect to the bench connector of the fundamental instrument and defining an alignment axis, wherein the receiver structure is further configured to permit, when the bench connector is connected to the receiver structure, an angular adjustment of the adjustment instrument relative to the fundamental instrument about an axis substantially perpendicular to the substantially planar superior surface of the bench connector, and a medial / lateral translational adjustment of the adjustment instrument relative to the fundamental instrument along the substantially planar superior surface of the bench connector; and (ii) a cutting guide connector oriented at a predetermined slope angle relative to the alignment axis of the receiver structure, the cutting guide connector configured to connect to a cutting guide. (i) a receiver structure configured to connect to the bench connector of the fundamental instrument and defining an alignment axis, wherein the receiver structure is further configured to permit, when the bench connector is connected to the receiver structure, an angular adjustment of the adjustment instrument relative to the fundamental instrument about an axis substantially perpendicular to the substantially planar superior surface of the bench connector, and a medial / lateral translational adjustment of the adjustment instrument relative to the fundamental instrument along the substantially planar superior surface of the bench connector; and (ii) a cutting guide connector oriented at a predetermined slope angle relative to the alignment axis of the receiver structure, the cutting guide connector configured to connect to a cutting guide.