A harness for attachment about a knee femur and comprised of a rigid and non-flexible frame support two resiliently mounted clamping means and sensors is described for the non-invasive measurement of knee motion and its analysis in 3-D is described. The clamping means elements are urged under pressure outwardly for application against a skin outer surface at predetermined medial and lateral sites relative to a femur. A non-resilient adjustable stabilizing element is connected to the rigid frame and disposed at a predetermined location with respect to the medial clamping element in spaced relationship therewith and adjustable for clamping contact on a skin outer surface and in alignment with the center of a medial condyle of the femur whereby to stabilize the rigid frame about a knee. An attachment rod is secured to the harness and has straps for securing the rod above the knee.