Described are computer-based methods and apparatuses, including computer program products, for implant planning using areas representing cartilage. A predetermined number of control points for generating a predetermined number of areas representing cartilage are determined, wherein the predetermined number of control points are based on an implant component. Measurements corresponding to a plurality of measured cartilage points are received, wherein each cartilage point is based on an associated control point from the predetermined number of control points. A plurality of areas representing cartilage are generated, wherein each area representing cartilage is larger than and projects to an associated control point from the plurality of control points. A representation of the implant component is positioned based on a representation of a bone, the representation of the bone comprising representations of the plurality of areas representing cartilage.