Osteoarthritis is a degenerative joint disease that can affect the knee. It causes the surface layer of cartilage to break down and wear away, and the joint's synovial fluid to lose its ability to lubricate. This combination causes pain, stiffness, limited joint motion, and inflammation in the knee. Osteoarthritis of the knee is often initially treated with pain relievers such as acetaminophen, nonsteroidal anti-inflammatory drugs and corticosteroid injections. However, these methods are not always effective, and can have adverse effects such as gastrointestinal problems, allergic reactions or kidney damage.
Viscosupplementation, in which injections of hyaluronic acid are used to improve knee function, is an alternative to pain medication for treatment of osteoarthritis of the knee. Those with osteoarthritis often have a low level of hyaluronic acid in their joints. Hyaluronic acid, which is a naturally occurring substance found in joint fluid, acts as a lubricant so that bones move smoothly, and as a shock absorber so that joints can bear weight. During viscosupplementation, hyaluronic acid is injected directly into the knee joint; it is typically administered in a series of 1 to 5 injections over several weeks' time. Benefits of viscosupplementation include the following:
- Reduction in pain
- Improved mobility
- Reduction in swelling and inflammation
- Effects that last for several months
It can take several weeks for patients to experience full symptom relief after hyaluronic-acid injections. Side effects associated with viscosupplementation are temporary, and include injection-site pain, swelling, redness and rash; bruising around the joint, or fluid accumulation in the knee. If these reactions occur, they are usually mild and do not last long. Viscosupplementation is most effective for mild-to-moderate cases of osteoarthritis, and may be a good option when osteoarthritis has not responded to conservative treatment with pain medication.