This reference is for surgeons and clinical teams reviewing Total Knee Replacement (TKR) plans in CustoMED. It defines each landmark and measurement used in preoperative planning and in the surgical plan.
Knee: Total Knee Replacement (TKR) (Mechanical/Anatomical)
All landmarks and measurements are derived from patient imaging and are intended to support planning, verification, and communication. They do not replace clinical judgment.
Note: In CustoMED, preoperative measurements appear in the Landmarks step and postoperative (surgical plan) measurements appear in the Surgery Planning step. Labels in the app can be shorter than the names in this guide.
Preoperative Landmarks: Femur
Femoral Anatomical Axis
Stage: Pre
Type: Landmark
Bone: Femur
Description: A line passing through the center of the femoral shaft, extending from distal to proximal, representing the femoral anatomical reference axis.
Femoral Mechanical Axis
Stage: Pre
Type: Landmark
Bone: Femur
Description: A line defined from the center of the femoral head to the center of the distal femoral notch, representing the load-bearing axis of the femur.
Knee Joint Line
Stage: Pre
Type: Landmark
Bone: Femur
Description: A line connecting the distal medial and lateral femoral condyles, representing the native knee joint line.
Transepicondylar Axis (TEA)
Stage: Pre
Type: Landmark
Bone: Femur
Description: A line connecting the medial and lateral femoral epicondyles, commonly used as a reference for femoral rotational alignment.
Posterior Lateral Condyle
Stage: Pre
Type: Landmark
Bone: Femur
Description: The most posterior point of the lateral femoral condyle, used to define the posterior condylar axis.
Posterior Medial Condyle
Stage: Pre
Type: Landmark
Bone: Femur
Description: The most posterior point of the medial femoral condyle, used to define the posterior condylar axis.
Preoperative Measurements: Femur
Femoral Mechanical-Anatomical Angle (FMAA)
Stage: Pre
Type: Measurement
Bone: Femur
Description: The angle between the femoral anatomical axis and the femoral mechanical axis.
Varus / Valgus (Femur)
Stage: Pre
Type: Measurement
Bone: Femur
Description: The angle between the femoral mechanical axis and the knee joint line, measured in the coronal plane.
Femoral Rotation
Stage: Pre
Type: Measurement
Bone: Femur
Description: The angular difference between the posterior condylar axis (PCA) and the transepicondylar axis (TEA).
TEA to AP Axis
Stage: Pre
Type: Measurement
Bone: Femur
Description: The angle between the transepicondylar axis (TEA) and the anteroposterior (AP) axis, defined from the femoral notch center to the trochlear center.
PCA to AP Axis
Stage: Pre
Type: Measurement
Bone: Femur
Description: The angle between the posterior condylar axis (PCA) and the anteroposterior (AP) axis.
Postoperative / Surgical Plan Measurements: Femur
Planned Varus / Valgus
Stage: Post
Type: Measurement
Bone: Femur
Description: The angle between the femoral mechanical axis and the distal femoral cutting plane, measured in the coronal plane.
Planned Flexion / Extension
Stage: Post
Type: Measurement
Bone: Femur
Description: The angle between the femoral mechanical axis and the distal femoral cutting plane, measured in the sagittal plane.
Planned Femoral Rotation
Stage: Post
Type: Measurement
Bone: Femur
Description: The angular difference between the posterior cutting plane and the selected rotational reference axis (PCA or TEA).
Femoral Distal Resection
Stage: Post
Type: Measurement
Bone: Femur
Description: The distance from the distal femoral cutting plane to the native knee joint line reference points.
Femoral Posterior Resection
Stage: Post
Type: Measurement
Bone: Femur
Description: The distance from the posterior femoral cutting plane to the posterior condylar axis (PCA) reference points.
Preoperative Landmarks: Tibia
Tibial Anatomical Axis
Stage: Pre
Type: Landmark
Bone: Tibia
Description: A line passing through the center of the tibial shaft, extending from distal to proximal, representing the tibial anatomical reference axis.
Lateral Tibial Plateau Center
Stage: Pre
Type: Landmark
Bone: Tibia
Description: The geometric center of the lateral tibial plateau surface.
Medial Tibial Plateau Center
Stage: Pre
Type: Landmark
Bone: Tibia
Description: The geometric center of the medial tibial plateau surface.
Tibial Plateau Plane
Stage: Pre
Type: Landmark
Bone: Tibia
Description: A plane defined by the medial and lateral tibial plateau surfaces, representing the native tibial articular surface.
Preoperative Measurements: Tibia
Varus / Valgus (Tibia)
Stage: Pre
Type: Measurement
Bone: Tibia
Description: The angle between the tibial mechanical axis and the tibial plateau plane, measured in the coronal plane.
Tibial Slope
Stage: Pre
Type: Measurement
Bone: Tibia
Description: The angle between the tibial mechanical axis and the tibial plateau plane, measured in the sagittal plane.
Postoperative / Surgical Plan Measurements: Tibia
Planned Varus / Valgus
Stage: Post
Type: Measurement
Bone: Tibia
Description: The angle between the tibial mechanical axis and the proximal tibial cutting plane, measured in the coronal plane.
Planned Tibial Slope
Stage: Post
Type: Measurement
Bone: Tibia
Description: The angle between the tibial mechanical axis and the proximal tibial cutting plane, measured in the sagittal plane.
Tibial Proximal Resection
Stage: Post
Type: Measurement
Bone: Tibia
Description: The distance from the medial and lateral tibial plateau centers to the proximal tibial cutting plane.
Tibial Rotation
Stage: Post
Type: Measurement
Bone: Tibia
Description: The angular alignment between the planned tibial insert orientation and the tibial anteroposterior (AP) axis.
Notes & Best Practices
All landmarks and measurements must be reviewed and approved by the clinician before final plan approval.
Osteophytes should be excluded when defining native articular surfaces and axes.
Measurements are provided for planning and verification purposes only and must be clinically validated by the surgeon.