Osteoarthritis is a highly prevalent disease, age being the main risk factor. The age-related accumulation of advancedglycation-endproducts (AGEs) adversely affects the mechanical and biochemical properties of cartilage. The hypothesis that accumulation of cartilage AGEs in combination with surgically induced damage predisposes to the development of osteoarthritis was tested in vivo in a canine model. To artificially increase cartilage AGEs, right knee joints of eight dogs were repeatedly injected with ribose/ threose (AGEd-joints). Left joints with vehicle alone served as control. Subsequently, minimal surgically applied cartilage damage was induced and loading restrained as much as possible. Thirty weeks after surgery, joint tissues of all dogs were analyzed for biochemical and histological features of OA. Cartilage pentosidine levels were $5-fold enhanced (p ¼ 0.001 vs. control-joints). On average, no statistically significant differences in joint degeneration were found between AGEd and control-joints. Enhanced cartilage pentosidine levels did correlate with less cartilage proteoglycan release (R ¼ À0.762 and R ¼ À0.810 for total and newly-formed proteoglycans, respectively; p ¼ 0.028 and 0.015 for both). The current data support the diminished cartilage turnover, but only a tendency towards enhanced cartilage damage in AGEd articular cartilage was observed. As such, elevated AGEs do not unambiguously accelerate the development of early canine OA upon minimal surgical damage. Keywords: osteoarthritis; non-enzymatic glycation; canine; pentosidine; proteoglycan Osteoarthritis (OA), with a high prevalence and increasing incidence due to the aging population, having a large impact on the patient's quality of life, is characterized by progressive cartilage damage, bone changes, and secondary synovial inflammation. 1 As yet, the pathogenesis of OA is largely unknown. Several factors have been reported to predispose to the development of OA, such as genetic background, overweight, joint laxity, and muscle weakness. 2 However, undisputedly, the most important risk factor for development of OA is age. 3 The incidence of OA increases strongly with age: >50% of the population over 60 years of age is affected. 4,5 However, there are still many uncertainties how age contributes to the onset and progression of OA. Age-related changes in the articular cartilage are suggested to play an important role in the susceptibility of cartilage to OA.One of the major age-related changes in articular cartilage is the spontaneous modification of proteins by non-enzymatic glycation resulting in the accumulation of advanced glycation endproducts (AGEs). Nonenzymatic glycation is a post-translational modification of proteins by reducing sugars. The spontaneous condensation of reducing sugars with free amino groups in lysine or arginine residues on proteins leads to the formation of AGEs. 6 Pentosidine, a fluorescent AGE formed between lysine and arginine residues, is frequently used as marker for AGEs. AGEs are formed in all pr...