Venous congestion in bone is a common early feature of inflammatory and degenerative joint diseases. An experimental study was performed of the relationship between the scintigraphic appearance of joints and the intraosseous hemodynamics during venous congestion caused by obstruction of the osseous venous drainage by increased intra-articular pressure. Intra-articular pressure was raised to 75% of mean arterial pressure in one knee each of 8 immature dogs. This caused elevated intraosseous pressure in the distal femoral epiphysis but not in the metaphysis. The elevated intraosseous pressure in the affected femoral epiphysis was associated with decreased technetium 99m diphosphonate uptake and blood flow, unaltered vascular volume and tissue hematocrit, and prolonged transit time of blood in the central cancellous bone. The decreased radionuclide uptake during intraosseous venous congestion thus appeared to reflect a decreased blood supply. However, by multiple regression analysis, the diphosphonate uptake in bone generally varied positively with blood flow and plasma volume and inversely with red cell volume in a nonlinear, multifactorial relationship.