In degenerative changes of the joints such as osteoarthritis, we observe a change in the quantity of hyaluronic acid (HA). Therefore, the cartilage is not protected adequately, which results in a gradual degradation of the cartilage and leads to symptoms of pain and restricted mobility. Normally, there is an exact balance between the breakdown of old hyaluronic acid and the production of new hyaluronic acid. In osteoarthritis, however, breakdown happens faster than production. As a result, the synovial fluid becomes more watery and stops working properly.
The hyaluronic acid gives the synovial fluid its characteristic physical properties. It plays an important role in shock absorption and acts as a filter, controlling the movement of cells and large molecules within the joint.
Under gradual shear stress, HA acts as a lubricant.
Under sudden loading, HA acts as a shock absorber.
HA forms a coating over the entire inner surface of the joint. This coating acts as a viscoelastic shield over the articular cartilage and synovium, protecting these structures from mechanical damage, as well as from free radical and other inflammatory factors.
In addition, HA forms the backbone of the proteoglycan aggregates that are essential for the structural and functional integrity of the articular cartilage (below is a diagram of the cartilage).
Hyaluronic acid plays a vital role in the healthy synovial joint.
