Plasma kinins in synovial exudates.

Kinin levels equivalent to 1-30 × 10 m bradykinin were found in 33 out of 82 exudates from rheumatoid joints. Only 2 of 27 fluids from joint effusions caused by osteoarthrosis or trauma, contained detectable levels of kinin (1-5 × 10 m bradykinin). The kinin concentrations showed little or no correlation with the white blood cell counts, protein concentrations and lactate dehydrogenase and acid phosphatase activities, in synovial fluids. Data on the pain felt in joints suggested that in higher concentrations kinins contribute to arthritic pain, but that other pain-producing factors are undoubtedly involved.