Electroarthrography: a novel method to assess articular cartilage and diagnose osteoarthritis by non-invasive measurement of load-induced electrical potentials at the surface of the knee  A.-M. Préville, P. Lavigne, M.D. Buschmann, J. Hardin, Q. Han, L. Djerroud, P. Savard  Osteoarthritis and Cartilage  Volume 21, Issue 11, Pages 1731-1737 (November 2013) DOI: 10.1016/j.joca.2013.07.003 Copyright © 2013 Terms and Conditions

Fig. 1 Positioning of the eight electrodes: on the medial side, two electrodes (#2 and 3) were placed over the joint line determined by palpation, another electrode was placed above (#1) and a final (#4) below these first two electrodes; electrode placement was similar on the lateral side (note that the lateral joint line may not be at the same height as that on the medial side). Osteoarthritis and Cartilage 2013 21, 1731-1737DOI: (10.1016/j.joca.2013.07.003) Copyright © 2013 Terms and Conditions

Fig. 2 Example low-pass filtered (5 Hz) EAG signals recorded at the eight electrode sites along with the inclinometer signal (bottom) from a Control subject who repeatedly shifted his weight from one leg to the other. A positive displacement for the inclinometer signal corresponds to the loading of the knee. During a 60 s interval, six compression cycles produced six positive rectangular pulses for all electrode sites, with the highest potential shifts at site 2 (0.3–0.4 mV). The vertical scale is 0.75 mV for the EAG. Osteoarthritis and Cartilage 2013 21, 1731-1737DOI: (10.1016/j.joca.2013.07.003) Copyright © 2013 Terms and Conditions

Fig. 3 Mean potential values (±95% confidence interval) at the eight electrode sites for the Control group (N = 20), the intact knee of the osteoarthritis group (N = 20) and over the knee prosthesis of the same OA patients. P-values: ** for P < 0.01, * for P < 0.05. Osteoarthritis and Cartilage 2013 21, 1731-1737DOI: (10.1016/j.joca.2013.07.003) Copyright © 2013 Terms and Conditions

Fig. 4 Finite element mesh for an electrostatic knee model (left) and simulated electric potential distribution over the knee surface (right). The simulated potential distribution is represented with an isopotential map: regions with the same color have the same potential with respect to the reference electrode, with increasing potential from blue (minimum: −0.09 mV) to red (maximum: +0.29 mV), which shows the same site of maximum potential (arrow) over the joint line as that measured in the Control subjects (electrode #2). Osteoarthritis and Cartilage 2013 21, 1731-1737DOI: (10.1016/j.joca.2013.07.003) Copyright © 2013 Terms and Conditions