TRPA1 and Arthritis: Semiquantitative scoring of composite arthritic changes in CFA-injected tibiotarsal joints found the severity of arthritis was significantly decreased in KO animals (WT ipsilateral joint: 4.4 ± 0.19 vs. TRPA1 KO ipsilateral joint: 2.63 ± 0.43) (Fig. 3b).