Viscosupplementation for osteoarthritis of the knee
Osteoarthritis is the most common form of arthritis in the world, affecting huge numbers of people and is a major cause of disability. As industrialized populations become older and live longer, the effects of osteoarthritis (OA) will become more marked.
New treatments are continually being developed as the understanding of OA moves forward rapidly.
Introduction to viscosupplementation
The synovial fluid is the fluid secreted by the lining of the knee and other synovial joints (most of our joints are of the synovial type). This fluid provides a useful function in the life of our knees.
One of the main constituents of synovial fluid, hyaluronic acid, gives viscosity and elasticity to the fluid, allowing it to improve the way joints function.
In OA this viscosity and elasticity is reduced, and this may contribute to the abnormal functioning of the joint.
Viscosupplementation has been developed to replenish the hyaluronic acid part of the synovial fluid. This has shown some promise in improving the pain and abnormal function of osteoarthritic knees.
Experiments have shown that adding hyaluronic acid to the cells in human synovial membrane stimulates them to produce hyaluronic acid themselves.
Hyaluronic acid as a lubricant and shock absorber in the synovial fluid. It is not toxic when injected, has few side effects and has a rapid onset of action.
Reason for using this technique
The concentration and molecular weight of hyaluronic acid in osteoarthritic joint fluid is reduced. Normal viscosity of the synovial fluid is vital to joint lubrication and is thought to have protective effects on the joint cartilage.
It is suggested that the changes in the synovial fluid in OA joints makes the joint cartilage more likely to be injured by physical or chemical stresses.
The aim of treatment
Injecting the materials into the joint is intended to increase the concentration and molecular weight of the hyaluronic acid towards the normal. The aim is to make the joint chemistry resemble more closely that of normal synovial fluid.
How does it work?
The mechanism of action of this therapy is not clear. A substance introduced into the knee may have a cushioning effect, but is thought not to last very long in the knee. However, its effect of stimulating normal production of hyaluronic acid from the joint lining could have longer term effects, including inhibiting the joint’s pain nerves from firing.
Hyaluronic acid may increase joint lubrication, control swelling and may encourage the production of cartilage.
Injection of hyaluran preparations has shown significantly greater pain relief than injection of a placebo, the effect is as good as taking anti-inflammatory medications. There is better pain relief than injection of steroids, and although this takes longer to develop it also lasts much longer.
Arthritis cost of treatment
Bobic (2003) showed the price of a course of injections costs £200-300 sterling, the average time of pain relief was seven months and 10% of people did not get any real pain relief. There were no significant complications.
Is the procedure safe?
Infection risk is very low if normal sterile technique is used. The treatment has no overall body effects so is an attractive treatment option for osteoarthritic knees. Overall the substances used are non-allergenic, non-toxic and do not cause inflammation.
Only Hyalgan TM has shown instances of anaphylactic shock-like reactions. Treatment can be followed by a few days of redness, pain, warmth and swelling, with occasional more severe inflammatory reactions needed steroid injection.
It may be unwise to inject patients who are sensitive to hyaluran materials or bird proteins, who have an infected area around the injection site, have circulatory problems in the leg or if there is strong inflammation present.
OA costs enormous amounts of money and if this treatment reduces or puts off the need for arthroscopic surgery or total knee replacement, there could be a considerable cost saving. This treatment seems to be developing into an important treatment for OA joints.
V Bobic: Viscosupplementation for the osteoarthritis of the knee