Mechanically sensitive Aδ nociceptors that innervate bone marrow respond to changes in intra-osseous pressure.
Twenty-five patients with pain in the knee or hip were examined by means of bilateral intraosseous phlebography, intraosseous pressure measurements and 99mTechnetium polyphosphate scintigraphy. All patients with typical rest pain--either due to osteoarthritis or to the intraosseous engorgement-pain syndrome--showed venous stasis and increased pressure in the bone marrow near the painful joint and abnormally high uptake of the radiotracer. In patients with other types of pain this correlation was absent. The results indicate that 99mTechnetium polyphosphate scintigraphy can be used as a screening method in the diagnosis of the intraosseous engorgement-pain syndrome in patients with a typical history. However, increased isotope uptake in a joint region may be due to a variety of other causes. The identical findings with all three methods of investigation in patients with the intraosseous engorgement-pain syndrome and osteoarthritis suggest a common pathomechanism.