RHEOLOGICAL BEHAVIOR : the key parameter to articulation supplements
The synovial fluid is a biological fluid highly concentrated in hyaluronic acid. This liquid is physiologically present in the joint and assumes both biological and physical functions essential for the joints. Depending on the mechanical stresses on the joints, the synovial fluid limits the friction between the bone parts thanks to its lubricating power and absorbs shocks thanks to its cushioning power. The synovial fluid's viscoelastic properties are due to the high concentration of hyaluronic acid. From a biological point of view, synovial fluid provides the nutrients and oxygen necessary for chondrocytes. In case of osteoarthritis, the biological and physical characteristics of the synovial fluid decline (2)(3)(4).
The rheological study of the synovial fluid analyzes its deformation and its flow under the effect of applied stresses. This study shows that the synovial fluid is a viscoelastic fluid. At low frequency, for example when walking, the synovial fluid behaves like a viscous and lubricating fluid whereas, at high frequency, its absorbs shocks.
Viscosupplementation is a therapeutic approach in case of osteoarthritis that consists in supplementing the deficient synovial fluid by injecting into the affected joint a hyaluronic acid gel with similar properties to that of the healthy synovial fluid. The clinical bibiography on viscosupplementation shows that this therapeutic approach reduces pain and stiffness, helps to restore joint mobility and may delay the need for surgery (1)(5)(6).