Synovial fluid glycosaminoglycan concentration does not correlate with severity of chondropathy or predict progression of osteoarthritis in a canine cruciate deficiency model.

OBJECTIVE

Considerable interest exists today in biochemical or immunochemical tests for monitoring the progression of osteoarthritis (OA). It has been suggested that measurements made on synovial fluid (SF) will more accurately reflect the magnitude of cartilage destruction in an index joint than those performed on serum. However, we have shown that the synovitis that occurs in OA affects the rate of protein clearance from the joint. We tested the hypothesis that if adjusted for clearance rate, the SF concentration of cartilage proteoglycans (PG) estimates severity of chondropathy and predicts progression of cartilage damage more accurately than if clearance is not taken into account.

METHODS

Clearance of radioiodinated serum albumin (RISA), a surrogate for the clearance of PG, was measured in 19 adult dogs at baseline and again 16 weeks and 32 weeks after anterior cruciate ligament transection (ACLT). Severity of chondropathy was determined arthroscopically after 16 weeks of instability and at postmortem 32 weeks after ACLT.

RESULTS

Adjustment for the RISA clearance rate showed that the SF PG concentration markedly underestimated the quantity of PG released from the OA cartilage. Regardless of whether the concentration was adjusted for clearance, no correlation existed between the SF PG level and the severity of chondropathy. Further, the SF concentration of PG 16 weeks after ACLT failed to predict severity of cartilage damage at postmortem.

CONCLUSIONS

SF concentration of a cartilage derived molecule is unlikely to predict the course of cartilage damage in an OA joint over time or in response to treatment with a potential disease modifying OA drug.