In this excerpt from a recent issue of the Johns Hopkins Arthritis Bulletin, Associate Professor Lynne C. Jones, Ph.D. talks about the importance of cartilage in the development of osteoarthritis.
In my experience here at Johns Hopkins, most patients have little awareness of cartilage until something goes wrong with it. And even then, they often have a limited understanding of what cartilage is and does, what can be done to protect joints from further damage, and what treatment options are available to help reduce pain and restore mobility. In many ways, that’s perfectly understandable.
Compared with most other body tissues and organs, cartilage is "out of sight and out of mind." Like a shock absorber in a car, it doesn't announce its presence until it becomes damaged and affects your ability to navigate the highways of everyday life.
Cartilage is an essential component of healthy joints. You may have experienced the pain and loss of mobility that occur when cartilage is damaged, either by a traumatic injury or by diseases such as osteoarthritis and rheumatoid arthritis. If so, you're not alone. Approximately 900,000 cartilage injuries occur each year in the United States and an estimated 20 million Americans are affected by osteoarthritis, most commonly in the knee.
Here are my answers to some the most common cartilage-related questions asked by patients.
Q. What is cartilage?
Dr. Jones: Cartilage is a translucent, connective soft tissue that's found in many areas of the body, including the joints, rib cage, spine, ear, nose, voice box, and bronchial tubes. This semitransparent substance is called hyaline cartilage, a name that derives from the Greek word hyalos, which means glass.
In normal joints, hyaline cartilage is a firm, rubbery material that covers and protects the ends of bones. Its primary components are water and two types of proteins—type II collagen and proteoglycans -- that together form a gel-like matrix that allows it to change shape when compressed. Cartilage also contains specialized cells called chondrocytes, which produce collagen, proteoglycans, and enzymes that help maintain healthy cartilage.
Q. Is aging inevitably associated with cartilage degeneration?
Dr. Jones: There are age-related cartilage changes. And yes, it seems that osteoarthritis is an age-related disease. That said, it still doesn’t mean that the changes due to aging are necessarily the changes that automatically lead to osteoarthritis. After age 60, a majority of men and women show some evidence of joint-space narrowing on X-rays (a sign of cartilage loss), but most of them have no osteoarthritis symptoms. Their cartilage is still fully functional.
