Abnormalities of respiratory gases in synovial fluid of patients with juvenile rheumatoid arthritis

Synovial fluids from 26 knees of patients with juvenile rheumatoid arthritis were analyzed for partial pressure of oxygen (pO2) and carbon dioxide (pCO2), pH, and for lactate. As in adult rheumatoid arthritis, a low Po2 level was associated with a high concentration of lactate (r = −0.81), and inverse relationships were demonstrated between levels of lactate and pH (r = −0.87), and pCO2 and pH (r = −0.86). These physiologic abnormalities were unrelated to the clinical severity of local joint disease or to the spread of joint involvement.