Lack of association between serum keratan sulfate concentrations and cartilage changes of osteoarthritis after transection of the anterior cruciate ligament in the dog

To determine whether the serum keratan sulfate (KS) concentration reflected the status of degenerating articular cartilage in a commonly used model of osteoarthritis (OA), serum KS levels were measured in 9 dogs prior to transection of the anterior cruciate ligament, 4 weeks later, and when the dogs were killed 8–14 weeks after surgery, at which time mild OA was present. In all cases, the serum KS levels were within the normal range. Values were not related to the cartilage uronic acid concentration, the rate of net 35 SO 4 glycosaminoglycan synthesis, or the histopathologic changes of OA. Although the serum KS concentration was not helpful as an indicator of the current status of the articular cartilage abnormality in the OA knee, serial samples from 6 dogs showed an increase of at least 10% over the baseline KS level at both timepoints following surgery ( P = 0.031 and 0.027). This presumably reflects changes in proteoglycan metabolism in the unstable knee, although the possibility of a systemic change in proteoglycan metabolism following cruicate ligament transection can not be excluded.