Osteoarthritis and Cartilage Vol. 15, Supplement C C75 from 52 joints of 16 normal Thoroughbred horses, collected bi- laterally from carpal joints of 10 horses (n=40), and MP joints of 6 horses (n=12). A previously validated commercially available immunoassay was used to determine equine SF BAP concen- trations. Results: SF BAP concentrations from the carpal joints of normal horses were 2.2 times higher than SF BAP concentrations from the MP joints of normal horses (P<0.05; Figure 1). SF BAP concentrations from OC injured carpal joints were 2.7 times higher than concentrations from OC injured MP joints (P<0.001). In addition, SF BAP concentrations from the OC injured carpal joints were significantly higher than from normal carpal joints (P<0.001). However, there was no significant difference between SF BAP concentrations from normal and OC injured MP joints. When combining the OC injured carpal and MP samples, SF BAP concentrations were positively correlated to the joint that was affected (R=0.554, P=0.0001). Figure 1. Scatter plot with mean synovial fluid BAP concentrations from nor- mal and osteochondral (OC) injured carpal joints (triangles) and metacarpo- /metatarsophalangeal (MP) joints (circles). Significant differences between groups are represented as *P<0.05 and ***P<0.001. Conclusions: Synovial fluid analysis of a bone biomarker such as BAP can be used to demonstrate joint specific differences in normal and OC injured joints. Acknowledgements: Study supported by the University of Florida Pari-mutuel Wagering Trust Fund 119 RELATIONSHIPS AMONG AND DISCRIMINATORY ABILITY OF INFLAMMATORY MEDIATORS IN SERUM AND SYNOVIAL FLUID IN A CROSS-SECTIONAL OSTEOARTHRITIS COHORT K. Ma 1 , F. Baribaud 1 , P.A. Marsters 1 , S. Visvanathan 1 , M. Mascelli 1 , X-y. Song 2 , S. Lohmander 3 , S. Blake 1 1 Centocor R&D Inc, Radnor, PA; 2 Ethicon R&D Inc, Somerville, NJ; 3 Department of Orthopedics, Clinical Sciences Lund, Lund, Sweden Purpose: Examine the relationships between inflammatory me- diators measured in serum and synovial fluid in a cross-sectional osteoarthritis cohort. Explore the ability of a marker or group of markers to distinguish among sub-groups in this cohort. Methods: A cross-sectional cohort composed of 6 different sub- groups including healthy volunteers (REF n=23), patients with either acute pyrophosphate arthritis (APA n=17), anterior cruci- ate ligament rupture isolated or combined with another ligament (LI n=146), meniscal tear (MT n=70), osteochondral fracture (OC n=19), primary knee osteoarthritis (OA n=46) for a total of 321 pa- tients. One sample of knee synovial fluid (SF) and serum (S) at 1 time point, varying between 0 days and 26 years after knee injury or onset of symptoms, were analyzed. Analytes measured using the Luminex platform included cytokines/chemokines, adipokines and acute phase proteins (LINCOplex assays, Millipore). Hierar- chical clustering was performed in the R statistical programming environment on the matrix of Hoeffding’s D statistics from serum and synovial fluid markers. Canonical discriminant analyses were performed on selected diagnostic categories using SAS. The fi- nal model arbitrarily selected the most predictive 10 markers from a stepwise procedure. All analyses used logarithmic-transformed values of the marker data. Results: Comparison of the 6 patient groups for all analytes in S showed that CRP and SAA levels were elevated in the APA group compared to all other groups (p<0.05). IL-6, CCL3/MIP-1α and GM-CSF levels were elevated in the OC group when compared to the LI, MT and OA groups (p<0.05) but not when compared to the REF or APA groups. The median level of CXCL8/IL-8 was also elevated in the APA and OC groups compared to all other groups (p < 0.05). Resistin concentration was elevated in the APA and OC groups compared to the LI, MT and OA groups (p<0.05) but not when compared to the REF group. Finally, CCL2/MCP-1 was significantly higher in the OA group when compared to the REF, LI and MT groups (p<0.05). Comparisons of the 6 patient groups for all measured analytes in SF showed that IL-6, Resistin and SAA levels were elevated in the APA group compared to all other groups (p<0.05). IL-8, IL-10, act-PAI-1 and CRP were elevated in the APA group (p<0.05) compared to all other groups except of the OC group. CXCL10/IP-10 was also elevated in the APA group when compared to all other groups (p<0.05) with the exception of the REF group. Finally, SAP was elevated in all groups (p<0.05) when compared to the REF group. Hierarchical variable clustering allowed identifying related pairs or groups of markers in both matrices but none was specific to any of the subgroups, nor did any cluster allow reclassifying the patients in their respective subgroups. However, when a discriminant analysis was performed using data for each marker in S and SF as well as their ratios, a set of 10 markers was capable of discriminating the patients belonging to the REF, APA and OA subgroups. Conclusions: While several individual, pairs or groups of mark- ers were found to be elevated within one or more subgroups or found to correlate in S, SF or both, no significant correlation could be established with any clinical parameter analyzed. However, a ten-marker set discriminated three subgroups (i.e. REF, APA and OA). 120 CARTILAGE BIOMARKERS IN URINE - ANALYSIS AFTER ANTERIOR CRUCIATE LIGAMENT TRANSECTION E. Lindhorst 1 , R.X. Raiss 2 , J. DeGroot 3 , N. Charni 4 , F. Juillet 4 , P. Garnero 4 , L. Wachsmuth 2 1 University of Marburg, Eppstein, Germany; 2 University of Frankfurt/Main, Frankfurt/Main, Germany; 3 TNO Quality of Life, Leiden, The Netherlands; 4 Synarc, Lyon, France Purpose: Cartilage biomarkers are expected to monitor changes of inheritable or spontaneous cartilage disease, after surgery or drug treatment. A frequently used animal model of osteoarthri- tis is transection of the anterior cruciate ligament (ACLT) of the rabbit which leads to osteoarthritis (OA) - like changes of the cartilage structure. In this study, different types of collagen degra- dation were examined in this ACLT - model. Collagenous degra- dation biomarkers were measured in urine: hydroxylysylpyridi- noline(HP), lysylpyridinoline(LP) and the C-terminal crosslinked telopeptide of type II collagen (CTX-II). Methods: New Zealand White rabbits were treated in two groups: transection of the anterior cruciate ligament (ACLT) and sham surgery. Each group consisted of 32 rabbits, 8 rabbits per group were sacrificed at 2, 4, 8 and 12 weeks respectively. A medial parapatellar approach was used to transect the ACL under complete visualisation. Sham surgery consisted of a com-