What is hyaluronic acid?
What is the function of hyaluronic acid in joints?
What is the medical use of hyaluronic acid in osteoarthritis?
Is hyaluronic acid useful?
Is it safe to use hyaluronic acid?
Hyaluronic acid is a glycosaminoglycan, a substance that is naturally present in human body. Its molecule can hold over 500 times of water. It is widely distributed, with especially high concentration in synovial fluid (joint fluid). It is also present in various connective tissues, skin and nerves.
Hyaluronic acid is a major component of synovial fluid. It increases fluid viscosity, and is responsible for its lubricating function.
It is also an important component of articular cartilage. It helps to maintain water inside cartilage, and is responsible for its resistance to compression.
In osteoarthritis, the components inside synovial fluid degenerate, losing their viscosity and lubricating function. As hyaluronic acid is a major component of synovial fluid, it is used as viscosupplementation by intra-articular injection, in an attempt to improve lubrication and decrease pain. Intra-articular injection of knee joint has been approved by FDA in USA. Hyaluronic acid is also available in an oral supplement form, but the effect is less direct.
Results of researches are mixed. While some researches support the efficacy of intra-articular hyaluronic acid injection in reducing pain for weeks to months, other researches show no difference. In general, it is believed that it may provide a temporary pain relief in early stage of osteoarthritis. However, it cannot halt or reverse the progress of osteoarthritis. In advanced stage of osteoarthritis with significant loss of cartilage, the effect is probably minimal.
In general there are not much severe side effects. There maybe pain at the site of injection. There may also be allergic reaction especially with oral forms. More severe side effects include joint infection after an injection or cardiovascular events, but these are quite rare.