Fig 3. Relationships between diagnostic variables in complete and partial cruciate rupture stifles to evaluate patterns of correlation between markers.

(A) In the complete CR stifle, correlations formed three clusters. Several inflammation markers were positively correlated with Synovial and Serum CRP concentrations, suggesting that inflammation promotes collagen degradation within affected stifles. Serum CRP was also positively correlated with histologic inflammation. In a second cluster, Radiographic effusion and OA were positively correlated with arthroscopic synovitis variables. In a third cluster, numbers of CD3⁺ lymphocytes were positively correlated with numbers of TRAP⁺ macrophages and neutrophils. (B) In the partial CR stifle, a larger number of positive correlations were identified that formed four clusters. Suppurative inflammation was positively correlated with CrCL ligament volume, assessed by MR imaging, and functional length of the ligament, suggesting that acute inflammation is related to ligament edema and loss of mechanical properties. In a second cluster, synovial and serum CRP concentrations were correlated with stifle TNCC, indicating that biochemical markers of inflammation correlate with inflammatory cell counts. In a third cluster, the synovial to serum CRP ratio was positively correlated several histologic markers of inflammation, suggesting that the synovial to serum CRP ratio is likely a clinically useful marker of stifle synovitis. In a fourth cluster, arthroscopic variables of inflammation were correlated with MR imaging measures of ligament fluid content, as measured by grayscale value, suggesting that early in the CR condition, synovitis may result in increased ligament fluid content. Abbreviations: TAS, Total Arthroscopic Score; ACVAS, Arthroscopic CrCL Fiber Damage Visual Analog Scale (VAS) score; AVAS, Arthroscopic Synovitis VAS score; CD3, CD3⁺ T Lymphocyte Grade; CrCLD, Radiographic length of CrCL normalized to patellar length; CRPR, C-reactive Protein (CRP) serum to synovial fluid ratio; FSEG, MR imaging CrCL FSE Grayscale; FSEV, MR imaging CrCL FSE Volume; FVIII, Synovial Factor VIII⁺ Vessel Grade; FVIIIVAS, Synovial Factor VIII⁺ Vessel VAS; Hgrade, Histologic Synovitis Grade; HVAS, Histologic Synovitis VAS Score; ICTPR, pyridinoline cross-lined carboxy-terminal telopeptide of type I collagen (ICTP) serum to synovial fluid ratio; JCRP, Synovial fluid CRP; JICTP, Synovial fluid ICTP; RADE, Radiographic Effusion score; RADOA, Radiographic OA score; SCRP, Serum C-Reactive Protein; SICTP, Serum ICTP; Supp, Suppurative Inflammation Grade; T1, MR imaging CrCL T1 Enhancement; TNCC, Synovial fluid total nucleated cell count; TPA, Tibial Plateau Angle; TRAP, TRAP⁺ Macrophage Grade; VIPRV, MR imaging CrCL VIPR Volume; VIPRG, MR imaging CrCL VIPR Grayscale.