Joints And Glucosamine Chondroitin

Your joints are dynamic structures, constantly challenged by the forces of gravity and repetitive movement. They are also relatively isolated from the rest of your body, their demand for adequate nutrition being offset by a need to exclude blood-borne bacteria and toxins. As people age, degenerative changes in their joints are relatively common. A 2001 review in "American Family Physician" reports that osteoarthritis is the most common form of arthritis in the world, with 80 percent of Americans affected by the time they are 65 years old.

Joint Anatomy

If you were asked to define what a joint is, you would probably describe a structure that anatomists call a diarthrodial joint. Diarthrodial joints consist of two bony surfaces abutting one another in such a fashion that they are movable, and the opposing bone surfaces are covered by an elastic tissue called cartilage. Diarthrodial joints, such as your shoulder, knee or hip, are surrounded by a tough, fibrous capsule that is lined by a thin membrane that produces a nutrient-rich, lubricating liquid called synovial fluid.

Cartilage Composition

Normal cartilage is composed of water, collagen and proteoglycans, which are complex combinations of protein and sugar molecules. Keratan and chondroitin sulfate are important proteoglycans in normal cartilage, and glucosamine is one of the basic building blocks for these proteoglycans. Embedded within the elastic cartilage matrix are cells called chondrocytes, which synthesize and excrete the various cartilage components. Cartilage is relatively devoid of blood vessels, so nutritional support for the chondrocytes is derived from the surrounding cartilage itself.

Loss of Cartilage

As your joints age, they tend to lose cartilage, because cartilage possesses a limited capacity for self-repair. Alternating compressive and decompressive forces are believed to pump fluid into your cartilage, but this is an inefficient way to deliver nutrients to deeper tissues. Young, healthy cartilage is renewed by the ongoing activity of chondrocytes, but this process declines with aging. An August 2000 review in "American Family Physician" demonstrates that aging also changes the consistency of the synovial fluid itself, which interferes with its ability to lubricate and nourish your joints.

Glucosamine and Chondroitin

Research evaluating the effects of supplemental glucosamine and chondroitin on osteoarthritis has produced conflicting results. One 2006 "American Family Physician" review suggested that glucosamine reduced pain and improved function in knee and hip osteoarthritis, but chondroitin did not appear to confer any benefit. A 2010 review in "British Medical Journal" found that neither glucosamine nor chondroitin were helpful for osteoarthritis and recommended that health insurers not pay for such treatments. Another 2010 review in "Rheumatology International" showed that both glucosamine and chondroitin slowed the progression of osteoarthritis, but only after two to three years of use.

Considerations and Recommendations

It is not clear how glucosamine and chondroitin work. Given the inconsistencies in benefit among various studies, it has not yet been determined if these agents exert any pharmacological or anatomical effects in arthritic joints. A 2008 review in "American Family Physician" suggested that glucosamine, at least, might stimulate new cartilage formation in damaged joints. The usual daily dose of glucosamine, either as a sulfate or hydrochloride, is 500 mg three times daily. Chondroitin dosage varies from 800 to 1,500 mg daily. If you have joint problems and think you would like to try glucosamine or chondroitin, check with your doctor.