Hyaluron

The mechanical properties of hyaluronic acid

Water retention

Hyaluronic acid has the ability, relative to its mass, to bind large quantities of water, up to six liters per gram.
For example, the vitreous body of the eye consists of 98 % water bound by only 2% hyaluronic acid.

Pressure resistance
Water is not compressible and this property is maintained in hyaluronic acid tissue, within which, as mentioned above, considerable quantities of water can be retained. This is generally true for much connective tissue and of special significance during fetal development, when stable structures have not yet developed. A further well-known example is the nucleus pulposus, the gelatin-like core of the spinal cord, which is able to support a large proportion of the body’s weight.

Lubricity
Hyaluronic acid is the main component of synovia (joint fluid) and serves as a lubricant in movements of the joints. It is further characterized by structural viscous properties: Its viscosity reacts to applied mechanical forces; specifically, its viscosity is reduced with increased shearing force. Further, it remains fluid but due to its high-molecular shape is sufficiently viscous to prevent it being extruded from the joint. Also, it “adheres” to the cartilage in the joint especially effectively due to chemical interactions and the external shape.
If, in the initial stages of a movement, for example when strong pressure is applied to the knee joint when jumping or standing, the molecules form balls and are suspended at the cartilage surface as in a ball bearing.