Colloid osmotic and hydrostatic pressures and energy metabolism in high-protein joint swelling. A preliminary study of traumatic effusions of the knee.

In 10 patients referred to arthroscopy with traumatic effusions of the knee, the protein concentration of the synovial fluid (SF) correlated to its colloid osmotic pressure (pi SF). The pi SF did not correlate to the poorly determined hydrostatic pressure (PSF) in extended or slightly flexed joints or to the SF volume (VSF). SF hypoxia correlated to pi SF and to the number of intra-articular erythrocytes, but not to the determined PSF or VSF. SF hypoxia correlated to increase in lactate and decrease in pH, fitting enhanced anaerobic glycolysis. In addition, SF erythrocyte counts correlated to lactate increase. During a 5-min period of high PSF induced by flexion, the PSF decreased, and even more markedly so after the joints had been rinsed with saline. The results suggest that rinsing of joints in order to lower the pi SF and to remove erythrocytes is of benefit in cases of traumatic effusion.