Systems, devices, and methods are described for locating and identifying anatomical landmarks, such as ligament attachment points, in image data. These systems, devices, and methods may provide an oblique plane that contains an anatomical landmark such as a ligament attachment point to the tibia. For example, the position at which the anterior cruciate ligament (ACL), medial collateral ligament (MCL) posterior cruciate ligament (PCL), or patellar tendon attaches to the tibia may be identified. The systems, devices, and methods allow for tracing of an anatomical landmark to generate a 3-D marking on a 3-D surface model of a patient's bone. The attachment points may be useful landmarks for patient-matched instrumentation.