A system for repairing a defect on a patient's articular surface comprising a guide, a guide pin, a reamer, and an implant. The guide is configured to be disposed about the defect and includes a passageway configured to establish a reference axis extending generally outwardly from the articular surface. The guide pin is configured to be received through the guide passageway along the reference axis and into bone beneath the articular surface. The reamer comprises a cannulated shaft configured to be advanced over the guide pin along the reference axis and further comprises a cutting surface configured to be rotated about the guide pin to form an excision site. The implant comprises a bone facing surface configured to be received in the excision site and a load bearing surface having a contour approximating a contour of the patient's articular surface.