The most widely accepted method to measure kneekinematics is using external movement registration with the aid of skin-mounted markers. However, a large error component appears due to skin movement relative to the underlying bone. The goal of this study is to use fluoroscopy to quantify skin movement artefacts in patients with a total knee prosthesis during a step-up task.

The most widely accepted method to measure knee kinematics is using external movement registration with the aid of skin-mounted markers. However, a large error component appears due to skin movement relative to the underlying bone. The goal of this study is to use fluoroscopy to quantify skin movement artefacts in patients with a total knee prosthesis during a step-up task.

Translational and rotational errors attributed to soft tissue movement were three times larger for the femur than for the tibia about allaxes. The mean of the absolute rotational differences for the femur were2.6, 3.3 and 1.7 degrees about the X, Y and Z axes respectively. Absolute peak differences for individual subjects were 9.1, 12.9 and 10.5 mm along the X, Y and Z axes respectively.

This is the first study examining the 3D relative motion between surface-mounted and bone-anchored markers without the use of cortical pins anchored to the tibia and/or the femur. The results revealed no regular pattern of soft tissue error between subjects indicating the unlikely success of numerical methods for modeling and removing soft tissue motion artifacts when using standard motion capture methods.