There are few reports in the literature about measurement of intraosseous venous pressure in bone. Necrosis of the femoral head was found to be related to higher intraosseous venous pressure. Values varied widely. Pain is thought to result when an individual critical intraosseous venous pressure is exceeded. From June 1986 to May 1987, 16 full-grown male rabbits were tested at the histological laboratory at the University of Innsbruck. The purpose of the study was to assess the intraosseous venous pressure of the patella and the revascularization and regeneration of cartilage following patella drilling. When animals were killed 3 months later, their patellas were filled with ink/gelatin. Histologically, there were numerous capillaries and new vessels in the drill-holes. The defect was filled with collagenous tissue. At the surface it differentiated into cartilage, similar to hyaline cartilage. Measurements of intraosseous venous pressure and phlebographies were also performed in four patellas in sheep at the research laboratory for experimental surgery in Davos, Switzerland. Intraosseous veins were filled with Biodur for further histological investigation.