Microendoscopy of the synovial vasculature in the rabbit knee joint.

The functional morphology of the synovial vasculature in the rabbit knee joint was investigated using our technique of microendoscopy, which involves an in vivo microscopy via a 1.9-mm endoscope. In the vessels of the fibrous tissue of the joint capsule it was found that after intraarticular administration of epinephrine the blood flow and the vascular diameters decrease for 3-5 min. In the areolar part of the synovial tissue, an external elevation of the intraarticular pressure causes collapse of the capillaries at 10-15 mm Hg, whereas the collapse pressure of the arterioles is 30-40 mm Hg. Intraarticular application of Neuropeptide Y (NPY) leads to a marked vasoconstriction including the arteriovenous anastomoses, whereas after epinephrine the arteriovenous anastomoses remain patent or dilate during the arteriolar constriction phase. It is concluded that the technique of microendoscopy allows a valuable in vivo investigation of the synovial microvasculature.