The association between changes in synovial fluid levels of ARGS-aggrecan fragments, progression of radiographic osteoarthritis and self-reported outcomes: a cohort study

Objective: To investigate whether change in concentrations over time of aggrecanase generated ARGS-aggrecan in synovial fluid (SF ARCS) associates with progression of radiographic knee osteoarthritis (OA) and patient-reported outcome in subjects with previous meniscectomy. Methods: We studied 141 subjects at two time points after meniscectomy. Time point A was on average 18 years after meniscectomy, time point B was on average 7.5 years later; 74 subjects had SF available from both examinations. We measured SF ARCS by an electrochemiluminescence immunoassay, graded radiographic features of tibiofemoral or patellofemoral OA according to the Osteoarthritis Research Society International (OARS!) atlas, and scored patient-reported outcomes using the Knee Injury and Osteoarthritis Outcome Score (KOOS). Using logistic regression (adjusted for age, gender, body mass index, time between examinations, and SF ARCS at first examination) we assessed associations between change in SF ARCS between first and second examinations and progression of radiographic OA and KOOS. Results: In subjects with decreasing SF ARCS between examinations, the likelihood of loss of joint space and worsening of KOOS pain between examinations was increased 6- and 4-fold respectively compared to those increasing in SF ARCS (odds ratio (OR) 5.72; 95% confidence interval (CI) 1.53-21.4 and 3.66; 1.01-13.2, respectively). No significant associations were seen between decreasing SF ARCS and progression of osteophytes (OR 0.88; 0.28-2.78), or for patient-reported outcomes other than KOOS pain. Conclusion: Having decreasing levels of SF ARCS over time was associated with an increased risk of loss of joint space and pain worsening, but showed no association with other patient-reported outcomes or osteophyte progression. (C) 2012 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.