Microcirculation of the juvenile knee in chronic arthritis.

In order to investigate pathogenetic factors in growth abnormalities of the knee in hemophilic arthropathy and juvenile rheumatoid arthritis, the hemodynamic changes of the knee following chronic synovial inflammation and elevated joint pressure were studied in puppies. Unilateral arthritis was induced by intraarticular injections of carrageenan solution. Regional blood flow (RBF) was measured by tracer microsphere technique. Microvascular volume (VV) was estimated from the distribution volumes of Cr51-labelled erythrocytes and I125 fibrinogen. Mean transit times (TT) of blood components were calculated from volume/flow ratios. The arthritic joint capsules were characterized by high RBF rates, increased VV, low tissue hematocrit (HCT) and short TT of blood. In the juxtaarticular epiphyses and the patella, RBF was largely unchanged, whereas VV was significantly elevated and TT of blood prolonged. The growth plates formed borders for the extension of these changes. The increased permeability and surface area between blood and bone in arthritis may accelerate the resorption and subsequent destruction of subchondral bone in chronic arthropathies of the juvenile knee.