When patients are diagnosed with osteoarthritis, their doctor usually launches into a discussion about cartilage damage or cartilage being worn away. What exactly is cartilage? What causes cartilage loss? Can cartilage be restored? Here are 10 things you should know about cartilage.
1 - There are three different types of cartilage -- hyaline, elastic, and fibrous.
Hyaline cartilage, also referred to as articular cartilage, is the type that is most familiar to arthritis patients. Hyaline cartilage is present in the joints, nasal septum, and airtube. Elastic cartilage is found in the ear, part of the nose, and the airtube. Fibrous cartilage is found in the meniscus.
2 - Cartilage is a tough but flexible tissue that has two components: water and matrix.
About 85 percent of cartilage is water but it decreases to about 70 percent in older people. The matrix is comprised of collagens, proteoglycans, and non-collagenous proteins. While cartilage is a highly-organized structure, the different types of cartilage have somewhat different properties that allow for specific functions in the body.
3 - Cartilage lacks a blood supply, nerves, and lymphatic system.
Chondrocytes are the only cells found in cartilage. Chondrocytes produce and maintain the cartilage matrix.
4 - Hyaline or articular cartilage is very smooth and has low friction -- allowing the bones in a joint to glide over one another upon movement.
Articular cartilage serves as the cushion within the joint, and as a shock absorber. When cartilage is damaged or worn away, the affected joint becomes painful, stiff, and limited in its range of motion.
5 - Cartilage damage can occur for various reasons. Growth or repair of cartilage unfortunately has limited potential.
If a joint is burdened by improper alignment, excessive weight, excessive activity, overuse, or injury, articular cartilage wears away.
6 - Progressive cartilage degeneration can cause pain and inflammation.
With severe osteoarthritis, articular cartilage can completely wear away so that the affected joint no longer has its cushion and it begins to rub bone-on-bone. In such cases, there is significant pain, loss of motion, and functional disability associated with the affected joint.
7 - Damage to articular cartilage can be seen on x-ray.
On x-ray, cartilage damage is seen as narrowing of the joint space between the bones that form the joint. In the knee, loss of articular cartilage typically correlates with loss of meniscal cartilage.
8 - Loss of articular cartilage causes extra stress on the ends of the bones that form the joint.
The extra stress on the ends of the bones in the joint can cause osteophytes, or bone spurs, to form at the margins of the joint.
9 - New techniques are being tried to restore articular cartilage.
Osteochondral grafting, autologous chondrocyte implantation, and mesenchymal stem cell regeneration are three techniques being used to restore articular cartilage. With osteochrondral grafting, a plug of bone and healthy cartilage is harvested from one area and then transplanted to the other site. Currently this is being used to treat knee injuries.
Autologous chondrocyte implantation involves the harvesting of healthy cartilage cells that are then cultivated and implanted at the injury site. This also is currently used for knee injuries.
Mesenchymal stem cell (MSC) regeneration is still experimental but it is thought that MSCs can be derived from bone marrow, placed in a gel matrix, and implanted at the site where new cartilage would develop.
10- Early detection and early treatment of osteoarthritis can help to prevent further cartilage damage.
The best chance for preventing or slowing cartilage damage comes with early treatment. Medications that are used to control osteoarthritis and other types of arthritis, joint protection techniques, and good body mechanics help to maintain healthy cartilage. Once joint damage becomes severe and interferes with daily living, joint replacement surgery may be the best option to restore function. Your doctor help you decide what's best for you.
Sources:Articular Cartilage. Joint Replacement Institute. Accessed 11/7/2007.
What Is Cartilage? International Cartilage Repair Society. Accessed 11/26/2007.
New Techniques to Restore Articular Cartilage. American Academy of Orthopaedic Surgeons. August 2007.