Know Your Joints And Glucosamine

By Dr Harold Gunatillake
Health Writer

When two adjoining bones in our body need function to move, nature gives us a perfect 'joint mechanism' for such action. Without such a mechanism, movement of limbs and other parts of the body will be not possible. The bone surfaces that form this mechanism rub against each other, leading to wear and tear. To minimize such friction, the joint surfaces need to be smooth and resistance free.

So, the surfaces are capped with smooth cartilages, a specialized form of connective tissue that has a cushioning effect between the joint surfaces. When you enjoy crunching your chicken bone ends, it is this cartilage that you crunch – so relish without damaging your teeth. When you look at it even in the cooked form, the cartilage has a white glistening glassy appearance. Microscopically, it is composed of water, collagen, proteoglycans, chondrocytes and other matrix protein and lipids.

It has no blood supply (avascular) and has no lymphatic system, thus being sheltered from the immune system. In short, the cartilage does not react to allergies as most other soft tissues in the body. This also means that foreign chemicals, even medication, may not influence the cartilage.

Most of the weight bearing joints like the hip, knee and ankle are synovial joints. A synovial membrane (showed in the diagram) is a thin tissue that lines the joint capsule on the inner aspect. This moist membrane or lining does not cover the cartilage surfaces. Synovial fluid is secreted from this membrane to lubricate the joints for smooth functioning. Hence, the articular cartilage gives synovial joints the ability to provide low-friction and pain-free motion.

Due to reduction in synovial fluid secretion with age, drying of the cartilage surfaces occur leading to early destruction.

More common would be over secretion of fluid due to chronic inflammation and degeneration of joint surfaces. This is most commonly seen in osteoarthritic knees where doctors would suggest tapping this lemon coloured jelly-like fluid.

These joints have no nerve supply and are, therefore, not sensitive to early injuries. The healing process after damage or degeneration is very slow. It has poor repair properties, because there are relatively few cells that facilitate healing in the tissue. The metabolic rate is low and the capacity of chondrocytes to divide and migrate in the articular cartilage is restricted by the matrix fibres. It is accepted that the articular cartilage does not repair significantly after injury or with degenerative changes.

Under these circumstances, it is difficult to believe that, by taking glucosamine and chondroitin orally, chemicals inherently available in the articular cartilages can repair the damaged or degenerating cartilage surfaces.

Osteoarthritic pain
For pain, paracetamol and aspirin have stood the test of time. Non-steroid anti-inflammatory drugs are contraindicated for patients taking blood pressure tablets, and platelet thinning tablets for heart disease, and those having kidney disease. Lastly, after suffering for years from osteo-arthritis, you may qualify to undergo surgery. Hips and knees are replaced with prosthesis that function well for at least ten years. This would give the ultimate pain-free night's sleep which you have been longing for.

This is a gradual disease characterized by a continual wearing of the articular cartilage, leading to exposure of the underlying subchondral bone. Rubbing of these damaged surfaces on weight bearing leads to severe aches and pains due to irritation of the nerves in the exposed subchondral bone. Management includes weight reduction, physical therapy like heat, ultra-sound, microwave therapy, and the use of non-steroidal anti-inflammatory drugs. Over-use of these drugs also cause much damage to the body including kidneys. Those with high blood pressure should avoid these drugs.

Chondroitin sulphate, belonging s to the carbohydrate family, is an essential component of articular cartilage. It comes from natural sources, such as shark or bovine cartilage, or it can be made in the lab. Chondroitin suphate is a combination of chondroitin and mineral salt. Glucosamine and chondroitin are normal components of the articular cartilage and claimed to promote the formation and repair of cartilage. Chondroitin is hypothesized as promoting cartilage repair due to water retention and elasticity it may cause.

This substance attracts fluid into the cartilage like a liquid magnet. Without this fluid, cartilage would become malnourished, thinner and more fragile. The resulting ample presence of water within chondroitin rich cartilage is supposed to increase the elasticity of the cartilage and, thereby, facilitates resistance to friction and the forces of impact. This hypothesis of water retention and its benefits have still not been proved. When chondroitin sulphate, being a large molecule taken orally, is degraded in the digestive system, it is most unlikely that chondroitin, per se, will be absorbed and dart straight to the joints to facilitate healing of the articular cartilage.

There are no studies that categorically answer the question of how glucosamine or chondroitin actually works in the body. The supporters of these chemicals claim a reduction in pain and swelling and faster soft-tissue healing but it is unclear how this is achieved.

Many people take both glucosamine and chondroitin for arthritic pains of the knee joint and swear by them, stating that both these chemicals do reduce the pain. Some studies show chondroitin alone may relieve pain and improve function of the affected knees.

There are also some studies that indicate glucosamine may help as much as ibuprofen (non-steroid anti-inflammatory drug) in relieving symptoms of osteoarthritis, particularly in the knee, with fewer side effects. Most studies have shown that both or either medication has no effect on rheumatoid arthritis and Lupus – an autoimmune condition. Rheumatoid arthritis affects the synovial membrane in the joints and the soft tissues around, causing deformities in the long term.

Though millions of people around the world take these medications, the prices are increasing and never come down with such large sales, unlike most other commodities.

The U S Food and Drug Administration does not regulate dietary supplements in the same way it regulates medication. Glucosamine and chondroitin, being classified as dietary supplements, need not be researched on their efficacy.

A major five year study by Clegg et al of over 1500 patients with osteoarthritis of the knee was completed in 2005. This was a randomized double-blind trial for patients taking glucosamine hydrochloride alone, chondroitin alone, a combination of both, an anti-inflammatory painkiller and a placebo.

This study was viewed by some as being one of the first rigorous trials of glucosamine and chondroitin. It found no overall benefit from taking glucosamine or only chondroitin or in combination in reduction of knee pain.

It is conclusively shown that glucosamine, chondroitin and their combination do not reduce joint pain or have an impact on narrowing of joint space. Health authorities and health insurers should not cover the costs of these preparations, and new prescriptions to patients who have not received treatment should be discouraged (BMJ Upgrades).

Side effects: It appears that glucosamine and chondroitin, in combination or separately, have few side effects. But people with osteoarthritis who have diabetes should talk with a doctor before they take glucosamine, because it is thought that glucosamine may influence blood sugar.

If you are allergic to shellfish, do not take glucosamine unless you have discussed it with your doctor.

Any dietary supplement may cause reactions with your conventional medicine you take. Discuss this with your doctor before starting on these supplements.

Pregnant women should not take a glucosamine supplement until more is known about interaction. Fortunately, most pregnant women are not at an age where they would be suffering from osteoarthritis.

On discussions with people both men and women at social gatherings, on questioning those who take both or either drug for osteoarthritis, the consensus of opinion would be that a third would say that there is some significant improvement, meaning less pain and swelling. A third would say, "We take it because our friends are on it". The rest would say that they are disappointed.

Some reference to & WebMD Medical Reference from Healthwise – June 27, 2007

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