Biochemical markers of arthritis are molecules detectable in synovial fluid, serum, or urine that may reflect an underlying degenerative joint disease. They also have the potential to be highly sensitive and specific to the degree of arthritis. There are 2 major categories of molecules used as biochemical markers of arthritis: molecules of the extracellular matrix and proteolytic enzyme or cytokines. Pyridinoline is a collagen crosslink synthesized in mature collagen and, belongs to the molecules of the extracellular matrix. Urinary pyridinoline has generally been used as a bone resorption marker. However, as pyridinoline is more abundant in cartilage and synovium than in other tissue, there is extensive literature describing the levels of urinary pyridinoline as a biochemical marker for cartilage destruction and metabolism, or arthritis. This paper will review the use of urinary pyridinoline as a marker for arthritis.