Contact force imbalance and contact kinematics (i.e. motion of the contact location in each compartment during flexion) of the tibiofemoral joint are both important predictors of a patient's outcome following total knee arthroplasty (TKA). Previous tibial force sensors (TFS) have limitations in that they either did not determine contact force and contact location independently in the medial and lateral compartments or only did so within restricted areas of the tibial insert, which prevented them from thoroughly evaluating contact force imbalance and contact kinematics in vitro. Accordingly, the primary objective of this study was to present the design and verification of an improved TFS which overcomes these limitations. The improved TFS consists of a modified tibial baseplate which houses independent medial and lateral arrays of three custom tension-compression transducers each. This TFS is interchangeable with a standard tibial component because it accommodates tibial articular surface inserts with a range of sizes and thicknesses. This TFS was verified by applying known loads at known locations over the entire surface of the tibial insert to determine the errors in the computed contact force and contact location in each compartment. The root-mean-square errors (RMSE) in contact force are =6.1N which is 1.4% of the 450N full scale. The RMSEs in contact location are =1.6mm. This improved TFS overcomes the limitations of previous sensors and therefore should be useful for in vitro evaluation of new alignment goals, new surgical techniques, and new component designs in TKA.