A new technique called electroarthrography (EAG) measures electrical potentials on the surface of the knee during joint loading. The objective of this study was to evaluate the effectiveness of EAG to assess joint cartilage degeneration.
EAG recordings were performed on 20 asymptomatic subjects (Control group) and on 20 patients with bilateral knee osteoarthritis (OA) who had had a unilateral total knee replacement (TKR), both the TKR knee and the remaining knee were analyzed. EAG signals were recorded at eight electrode sites over one knee as the subjects shifted their weight from one leg to the other to achieve joint loading. The EAG signals were filtered, baseline-corrected and time-averaged.
EAG repeatability was assessed with a test-retest protocol which showed statistically significant high intraclass correlation coefficients (ICC) for four electrode sites near the joint line. These sites also showed the highest mean EAG values. The mean EAG potentials of the Control group were significantly higher compared with the OA group for three sites overlying the joint line. The potentials overlying the TKR were statistically nul. In the Control group, no statistically significant correlation was found between the EAG amplitude and age, weight, height or body mass index (BMI); no statistical difference was found in mean EAG potentials between women and men.
This study indicates that EAG signals arise from the streaming potentials in compressed articular cartilage which are known sensitive indicators of joint cartilage health. EAG is a promising new technique for the non-invasive assessment of cartilage degeneration and arthritis.