Effect of Repeated Arthrocentesis on Cytology of Synovial Fluid

Repeated arthrocentesis is necessary to diagnose and monitor the evolution of joint diseases, but the procedure may worsen any inflammation and lead to an alteration in synovial fluid. The aim of this study was to determine the effect of repeated arthrocentesis on synovial fluid cytology in healthy horses with normal joints. The experimental study was approved by Ethics Committee (University of Pisa, Italy). Four horses were enrolled in this study on the basis of inclusion criteria and underwent repeated arthrocentesis of the intercarpal joint of both left and right forelimbs. The synovial fluid samples were processed for total protein concentration, total nucleated cell count, and differential leukocyte count. Data distribution was performed with the Komolgorov–Smirnov test, and a Friedman test for repeated measures and Dunn's test as post hoc were performed in order to verify differences related to sampling times comparing each time point. Significance was set at P <.05. All horses remained free of lameness throughout the study period. Statistical differences were found for macrophage and lymphocyte related to sampling time. Our results support the finding that repeated arthrocentesis does not induce detectable synovial fluid alterations. Although mild statistically significant changes in macrophage and lymphocyte populations were found, the values were always within normal ranges, suggesting that these changes were not clinically significant. Moreover, the cytologic alterations rapidly solved. In conclusion, repeated arthrocentesis does not cause long term and clinically relevant alterations in synovial fluid cytology in healthy horses with normal joints.