An orthopaedic surgical device for measuring a joint force of a patient's knee joint, the orthopaedic surgical device comprising: a tibial paddle shaped to be positioned between the proximal end of a patient's tibia and the distal end of a patient's femur, the tibial paddle having a substantially planar upper surface and a substantially planar bottom surface, a sensor array positioned in the tibial paddle and configured to generate sensor signals indicative of a joint force between the patient's tibia and femur, an elongated handle secured to the tibial paddle and defining a longitudinal axis that is offset from an anterior-to-posterior bisecting axis of the tibial paddle, a first display secured to an end of the handle distal from the tibial paddle, and a circuit positioned in the handle, the circuit being configured to receive the sensor signals from the sensor array and to control the first display to provide a visual indication of the medial-lateral balance of the joint force, characterised in that the sensor array comprises a plurality of medial-anterior capacitive sensors to measure a medial-anterior force component of the joint force, a plurality of medial-posterior capacitive sensors to measure a medial-posterior force component of the joint force, a plurality of lateral-anterior capacitive sensors to measure a lateral-anterior force component of the joint force, and a plurality of lateral-posterior capacitive sensors to measure a lateral-posterior force component of the joint force, wherein each of the medial-anterior sensors has a surface area which is approximately equal to the surface area of each of the lateral-anterior sensors, and each of the medial-posterior sensors has a surface area which is approximately equal to the surface area of the lateral-posterior sensors. a tibial paddle shaped to be positioned between the proximal end of a patient's tibia and the distal end of a patient's femur, the tibial paddle having a substantially planar upper surface and a substantially planar bottom surface, a sensor array positioned in the tibial paddle and configured to generate sensor signals indicative of a joint force between the patient's tibia and femur, an elongated handle secured to the tibial paddle and defining a longitudinal axis that is offset from an anterior-to-posterior bisecting axis of the tibial paddle, a first display secured to an end of the handle distal from the tibial paddle, and a circuit positioned in the handle, the circuit being configured to receive the sensor signals from the sensor array and to control the first display to provide a visual indication of the medial-lateral balance of the joint force, characterised in that the sensor array comprises a plurality of medial-anterior capacitive sensors to measure a medial-anterior force component of the joint force, a plurality of medial-posterior capacitive sensors to measure a medial-posterior force component of the joint force, a plurality of lateral-anterior capacitive sensors to measure a lateral-anterior force component of the joint force, and a plurality of lateral-posterior capacitive sensors to measure a lateral-posterior force component of the joint force, wherein each of the medial-anterior sensors has a surface area which is approximately equal to the surface area of each of the lateral-anterior sensors, and each of the medial-posterior sensors has a surface area which is approximately equal to the surface area of the lateral-posterior sensors.