Precision Assessment of B-Mode Ultrasound for Non-Invasive Motion Analysis of Knee Joints

Measurement of the motion of the components in normal and artificial knee joints is a major goal of the orthopaedic research community. Abnormal motion in knee joints is a major cause of pain and often leads to chronic injury. Currently the standard way to measure the motion with enough accuracy is by implanting tantalum beads in the bones prior to imaging using X-ray equipment. However this technique is invasive and exposure to ionizing radiation imposes a significant cancer risk. Moreover, during the procedure the patient cannot perform normal everyday activities due to their confinement to the limited field of view of the X-ray equipment. In this paper we propose a novel non-invasive approach to measure knee motion using 2D B-mode ultrasound and image registration. Our results show that this approach has the required precision for reliable motion analysis without the need for implanting beads and can be used while the patient performs normal activities.