Fig. 1

Lameness scores and total protein (TP), white blood cell (WBC), and prostaglandin E₂ (PGE₂) concentrations in the synovial fluid of middle carpal joints (MCJ) and tarsocrural joints (TCJ) following IL-1β-induced synovitis or intra-articular lavage. Forelimb lameness, as measured by mean vector sum using an inertial motion sensor system, increased markedly from baseline for 12 h post-induction of synovitis on the synovitis limb (a). Hind limb lameness as measured by pushoff factor showed that horses started the study with a trend toward mild lameness of the contralateral hindlimb (negative values) in the first week but became sound (− 2 to + 2) in the last 4 weeks of the study (b). TP increased from baseline for 72 h following synovitis induction and was greater in synovitis MCJ as compared to contralateral MCJ for 4 weeks post-synovitis induction. TP decreased from baseline at 5 weeks post-induction (c). TP increased from baseline for 72 h following lavage with no differences from contralateral TCJ. TP decreased from baseline at 3 and 4 weeks post-lavage (d). WBC counts increased from baseline and were greater in synovitis MCJ as compared to contralateral MCJ for 1 week post-synovitis induction (e). WBC counts increased from baseline for 72 h following lavage with no differences from contralateral TCJ (f). PGE₂ increased from baseline for 24 h following synovitis and was greater in synovitis MCJ as compared to contralateral MCJ for the majority of 2 weeks post-synovitis induction (g). Following lavage, PGE₂ increased from baseline at 6 h and was greater in lavage TCJ as compared to contralateral TCJ at 6 and 24 h post-lavage (h). An asterisk indicates a difference from baseline, and a triangle indicates a difference from the contralateral limb at the same time point. Graphed values are marginal means +/− SEM