Abstract: The present invention provides methods and apparatus that permit one to accurately measure range of motion of a joint for joint stability testing and other purposes. In accordance with one aspect of the invention, a marker that can be tracked by a surgical navigation system is rigidly fixed to each of the bones forming a joint and the joint is placed within the field of view of the surgical navigation system. The surgical navigation system tracks the bones in all six degrees of freedom by tracking the markers attached thereto. The navigation system can be programmed to measure and display to the surgeon all information relevant to such joint stability testing, including, but not limited to, starting position, maximum joint translation, maximum joint rotation, instantaneous joint translation, instantaneous joint rotation, and instantaneous joint flexion angle. The system may be set up to show a comparison of pre- and post-operative data.

Abstract: In order to conduct navigation-assisted knee operations in a simple and optimum manner, a patella reference device is proposed for the determination of the spatial position of a patella of a human knee joint during a navigation-assisted surgical procedure, comprising a base unit that can be secured on the patella, a reference element that can be detected by a detection device and a connecting device for the detachable connection of the base unit and the reference element in a first reference position and in at least one further second reference position differing from the first reference position.