Cartilage is a tough, flexible connective tissue that is found throughout the body. This rubbery tissue which covers the ends of long bones functions mainly as a cushion for joints. It also, because it is covered by a thin layer of lubricating material called "synovial fluid" also acts to allow gliding of joints.Osteoarthritis is a disease of cartilage. The cartilage becomes damaged and begins to wear away.

Cartilage does not have a blood or nerve supply... As a result, unlike damaged skin or muscles or other organ systems that can heal, damaged cartilage early on does not cause pain and will not heal quickly.

There are three types of cartilage:

•Elastic cartilage is a pliable form of cartilage found in structures such as the outside of the ears, nose, and epiglottis.

•Fibrocartilage is a tough type of cartilage and is very shock resistant. It is found in the discs that form part of the spinal column and also is the type of cartilage that makes up the meniscus (ring of cushion material) located in the knees, hips, and shoulders.

•Hyaline cartilage is a softer type of cartilage that is found most commonly in joints.

Cartilage damage is not painful early on, since no nerve fibers are present. However, as the problem progresses and develops into arthritis, there are symptoms which do occur.

Symptoms of articular cartilage damage include:

•decreased range of movement in the affected joint

•joint pain

•stiffness with inactivity

•swelling

If the damage is particularly severe, a piece of cartilage can break off and become loose. In this case, the loose piece of cartilage may affect the movement of the joint. This can cause a feeling of 'locking' or catching. Sometimes, the joint may also give way.

Articular cartilage damage can occur as a result of trauma- a direct blow to the cartilage. This is why cartilage damage is often a problem for people who play contact sports.

Cartilage can also become damaged gradually, over time. There is an increased risk of developing this type of cartilage damage for heavy individuals, or for people with an anatomic abnormality which causes a structural problem with the joint.

Interestingly enough, immobility can also damage the cartilage.

The major problem when damage occurs to cartilage is that articular cartilage has a very limited capacity for self repair. A small amount of damage does not repair itself and often gets worse over time.

The diagnosis of cartilage damage can be suspected by a careful history and physical examination. Confirmation can be obtained by diagnostic studies such as:

• Magnetic resonance imaging (MRI): MRI scans use strong magnetic fields to produce detailed images of the inside of the body. It can often detect cartilage damage.

•Diagnostic ultrasound: This relatively new method of musculoskeletal diagnosis uses sound waves to image cartilage and inflammation.

•Arthroscopy: This is a form of surgery where an arthroscope- a small telescope is used to look inside the joint.

•X-ray: While this is the traditional method of imaging, the drawback is that osteoarthritis has to be relatively severe before it shows up on x-ray.

There are a number of treatments that can help to relieve the symptoms of damaged articular cartilage. Nonsurgical approaches include:

•Non-steroidal anti-inflammatory drugs (NSAIDS) help with pain and inflammation. They do have potential side effects that require close monitoring.

•Physical therapy. Various types of treatments such as electrical stimulation, diathermy, and ultrasound,can reduce pain. And exercises which strengthen the muscles supporting the joint may help to reduce the pressure on the joint, and reduce pain.

•Assistive devices. Canes, walkers, and braces are sometimes useful.

•Lifestyle changes. Weight reduction, regular exercise, and so on can be useful.

•Corticosteroid injections can reduce pain and swelling temporarily but should not be given in the same joint more than 3 times per year.

•Viscosupplments are special lubricants that may dramatically improve pain and mobility when injected into a joint. It is strongly recommended that steroid and viscosupplement injections be given using ultrasound guidance to ensure proper placement of injections.

When non-surgical approaches aren't enough, then surgical treatments may be required.

Arthroscopic lavage and debridement employs an arthroscope to wash the joint out. The technique cannot repair the damaged cartilage, but it can help to reduce the pain and increase mobility.

Microfracture surgery: This is a procedure that involves drilling tiny holes (micro fractures) into the bone underneath the damaged cartilage. This exposes the blood vessels inside the bone. Blood cells then begin to stimulate the production of new cartilage. The disadvantage is that the newly formed cartilage is fibrocartilage rather than hyaline cartilage. Fibrocartilage is not as strong as hyaline cartilage. Therefore, it can wear away more quickly than hyaline cartilage.

Mosaicplasty: This is a technique that involves removing healthy cartilage from the non-weight bearing areas of a join and using it to replace damaged cartilage.

Autologous chondrocyte implantation (ACI) : This is a technique where a small sample of cartilage cells is taken from the non-weight-bearing part of the knee. The cells are sent to a laboratory where they are stimulated to divide and produce new cells. After a few weeks, the number of cartilage cells will have increased by about 50-100 times from their original number. The new cartilage cells will then be placed under a flap of material that is sewn over the damaged part of the joint.

For patients where cartilage has worn away completely, total joint replacement is probably the procedure of choice. While it is successful for most people, there are potential complications such as infection, blood clots, and prosthesis failure which can occur.

There are a number of research projects that are currently investigating additional efficient and effective ways of repairing cartilage.

•Hybrid cartilage is an investigational procedure where human cartilage cells are combined with synthetic fibers to form a patch.

•Stem cells: Another area of research is looking at ways of using special cells, known as stem cells, to generate new cartilage. This latter procedure is promising. Unfortunately, only a few centers worldwide have the knowledge and expertise to perform this procedure properly.