CTSK and rheumatoid arthritis: CTSK, P SKAT.corr = 0.0062 and Pburden.test.corr = 0.0034, ORburden.test = 0.28 and CI95%.burden.test = (0.1, 0.68), is highly expressed by rheumatoid synovial fibroblasts (RSF) that are activated by toll-like receptor signaling pathways in rheumatoid arthritis and is known to play a key role in the degradation of type Iand type II collagen.