Disclosed herein are unicompartmental femoral and tibial arthroplasty jigs for respectively assisting in the performance of unicompartmental femoral and tibial arthroplasty procedures on femoral and tibial arthroplasty target regions. The femoral and tibial unicompartmental arthroplasty jigs each include a first side, a second side and a mating surface. Each second side is generally opposite its respective first side. For the femoral jig, the mating surface is in the first side of the femoral jig and configured to matingly receive and contact a generally planar area of an anterior side of a femoral shaft generally proximal of the patellar facet boarder and generally distal an articularis genu. The first side of the femoral jig is configured to be oriented towards the femoral arthroplasty target region surface when the mating surface of the femoral jig matingly receives and contacts the planar area. For the tibial jig, the mating surface of the tibial jig is in the first side and configured to matingly receive and contact a generally planar area of an anterior side of a tibial shaft distal of the tibial plateau edge and generally proximal of the tibial tuberosity. The first side of the tibial jig is configured to be oriented towards the tibial arthroplasty target region surface when the mating surface of the tibial jig matingly receives and contacts the planar area.