Anatomie et physiologie : recherches en cours
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Concepts of Etiologies and Effects of Normal Human Knee Pressure Variations

William O Irvine

Background: Etiologies of pressure variations in the human knee have not been established. Most contend that condylar cartilage nutrition is primarily achieved through diffusion. This remains unsettled. Methods: Proposed etiologies are revealed through studies by others on knees of rabbits, dogs, and humans, as well as clinical examination and evaluation of magnetic resonance imaging. Results: Volume studies of the normal knee infra-patellar fat pad reveal that when moving from 0° to 35°, substantial volumes of gross loculated mostly peri-patellar-femoral synovial fluid is discovered. Accordingly, the volume of infra-patellar fat pad plus its associated synovial fluid increases 22.6%. Conclusion: Knee pressure variations during motion are fundamental. They are caused by macro-anatomic changes of the knee while functioning as a bellows. The knee is closed except that arterial blood enters and venous blood as well as lymph exit in response to intrinsic pressure-volume changes with motion. In addition to experiencing motion and load transfer, the knee is a hydraulic pump that by moving fluids in and out as well as within itself is primary in condylar cartilage nutrition. Proposed physiologic benefits of knee pressure variation in addition to condylar cartilage nutrition include joint stability and vascular flow. Clinical relevance: Given active trans-synovial hydrodynamic solute loaded fluid flow is primary in anabolic and catabolic condylar cartilage nutrition, new considerations may be offered while investigating enigmatic auto-immune synovitides.