We bend our knees a million times in a year. The lubricating fluid, called synovial fluid, helps this process acting like a lubricant and shock absorber to protect your knee. To understand viscosupplemention and its benefits, let's take a look at the normal knee and osteoarthritis (OA).

   The knee joint is where the femur (thigh bone) and tibia (shin bone) come together. A third bone, the triangular-shaped patella (kneecap), lies across the front of the joint to protect it. As in our other joints, a layer of protective cartilage covers the ends of the bones to allow smooth movement. Special to the knee are two pads of protective tissue called menisci. The entire joint is encased is a capsule lined with a membrane called the synovium which generates a fluid that acts as both a lubricant and a shock absorber. This fluid is called synovial fluid. Various ligaments and muscles support, stabilize and power the joint.

   Although there are many problems associated with knee pain, the most prevalent joint disorder is osteoarthritis. Osteoarthritis can be due to a predisposition to its development but also often is a result of repetitive micro traumas over many years, an injury left untreated such as a torn meniscus and being overweight. The end result of osteoarthritis of the knee is often severe cartilage loss resulting in significant pain particularly while weight bearing (walking), getting up from a chair and sometimes at night.

   Through this process of progressive osteoarthritis, the components of the synovial fluid often breakdown, resulting in diminished shock absorbing characteristics. This loss of shock absorption results in less protection of the knee during movement. One such component of the synovial fluid is hyaluronic acid (HA), which is responsible for the synovial fluid's ability to lubricate and act as a shock absorber in the knee. When one has knee OA, the concentration of HA in the synovial fluid is reduced causing a loss of shock absorbing and lubricating properties. This results in increased joint pain, stiffness and possibly an onset or worsening of osteoarthritis.

What is Hyaluronic Acid?
   Hyaluronic acid (HA) is a substance natural in the body and is present not only in the synovial fluid but also in the eyeballs, skin and cartilage. When isolated, it is a thick, viscous solution. Viscosupplements, which are designed to replace osteoarthritic synovial fluid with a more normal prosthetic synovial fluid, use purified HA derived from either rooster combs or genetically engineered cells to add to the natural HA in the knee joint.

The Role of Viscosupplementation
   Viscosupplementation is an option of treatment for those with moderate to moderately severe osteoarthritis of the knee. Through a series of injections, supplemental HA can be added to the knee joint. It is believed that by replacing the osteoarthritic synovial fluid with a product made of HA that is closer to normal synovial fluid, the patient experiences pain relief due to the presence of a new "lubricant" in the knee that is also acting as a shock absorber. The result is increased protection of the knee joint itself and a soothing of the nerve endings exposed by the degraded cartilage of the osteoarthritic knee.

Could You Benefit?
   Viscosupplementation is given to people with knee osteoarthritis who have not responded to traditional therapies, such as oral anti-inflammatory or analgesic medications or exercise. It is also can be considered for those who are trying to delay or simply are not candidates for total knee replacement surgery. This treatment has not been approved for other joints, although there are studies underway for hip arthritis.

How Is It Administered?
   Viscosupplementation therapy is only available through injection into the knee. The injection is given directly into the knee from a point on the side and under the kneecap. Synvisc is a viscosupplementation product that is specifically designed to be closest to healthy young synovial fluid and provides relief that can last for months. It is given in a series of three injections, one each week. It can take up to 12 weeks to take full effect.

Is There Any Risk?
   If you have had any allergic reaction to any hyaluronate preparations or are allergic to poultry products, you are not a candidate for these injections. You also should not receive these injections if you have an infection or skin disease around the injection area. Sometimes one can experience some swelling, heat, redness or itching around the joint, but this is temporary. Any reaction is usually mild and short-lived.

Does Viscosupplemention Work?
   HA viscosupplemention is a safe and effective treatment for osteoarthritis of the knee. Depending on the severity of the knee arthritis, these injections can be 72-75% effective for six months to a year.

   If you wonder whether you are a candidate or could benefit from viscosupplemention, see your orthopaedic surgeon or rheumatologist for an evaluation of your options.

About the Author:
   Arizona orthopaedic surgeon, Dennis Armstrong, M.D., is board certified in orthopaedic surgery and specializes in arthritis reconstructive surgery. He received his medical degree from the Wayne State School of Medicine and completed his orthopaedic residency at Henry Ford Hospital in Detroit, Michigan. Dr. Armstrong has been involved in several clinical investigative studies researching the surgery and care of those undergoing total joint replacement, and has authored numerous talks/papers on options for knee and hip pain.

© Copyright 2005. Arthritis Education by Professionals, Inc.