Effect of simulated joint effusion on subchondral haemodynamics and metabolism.

The purpose of the present study was to investigate the effect of simulated joint effusion on pO2, pCO2, the regional blood flow and intraosseous bone marrow pressure in the subchondral bone of rabbit. Mass spectrometry was used for simultaneous and continuous registration of subchondral pO2 and pCO2, while the relative argon signal was used for qualitative estimation of regional bone blood flow. The bone marrow pressure was recorded continuously by pressure transducers. Isotonic sodium chloride infusion at a constant pressure of 75 mmHg into the knee joint cavity constituted the basis for joint effusion. An instant increase in the subchondral bone marrow pressure followed the joint effusion (P less than 0.001). This resulted in a significant (P less than 0.01) decrease in the qualitative bone blood flow, significant (P less than 0.01) hypoxia and significant (P less than 0.01) hypercapnia in the subchondral bone. Joint effusion always lasted 30 minutes. Following its release all changes were reversed to normal values within 15 minutes. Within the period of observation no nervous or humoral factors seem to be brought into action. It was concluded that regional venous stasis was responsible for all changes, and that joint effusion should not be left untreated for long periods.