Articular cartilage is the smooth, white tissue that covers the ends of bones where they come together to form joints. Healthy cartilage in our joints makes it easier to move. It allows the bones to glide over each other with very little friction.
This articular cartilage surface can be damaged by trauma such as a sports injury. Normal use, including running, won’t wear out the cartilage unless it’s been previously injured or if the meniscus cartilage has been removed. Bone malalignment or being overweight can also contribute to damage. The diseases of osteoarthritis and inflammatory arthritis can directly damage the cartilage surfaces as well.
Once damaged, articular cartilage will not heal on its own. Over time, the cartilage breaks down and the underlying bone reacts. As the bone stiffens and develops bone spurs, (osteophytes) the joints become inflamed and swollen, which damages the cartilage even more, leading to pain, swelling or loss of motion.
Although articular cartilage damage diagnosis may sometimes be extremely challenging, modern non-invasive tests make the job much easier than it used to be. Differentiating between cartilage damage in the knee and a sprain or ligament damage is not easy, because the symptoms overlap.
After carrying out a physical examination, the doctor may order the following diagnostic tests:
Magnetic resonance imaging (MRI)
The device uses a magnetic field and radio waves to create detailed images of the body. It can often detect cartilage damage. However, in some cases, the damage cannot be seen on the MRI, even though it is present.
A tube-like instrument (arthroscope) is inserted into a joint to inspect and diagnose it. Repairs can also be carried out. This procedure can help determine the extent of cartilage damage.
Surgical options include:
Under the damaged cartilage the surgeon drills tiny holes (micro fractures), exposing the blood vessels that lie inside the bone. This causes a blood clot to form inside the target area of the cartilage. The blood cells trigger the production of new cartilage. One drawback is that this procedure does not produce the desired type of cartilage – fibro cartilage instead of hyaline cartilage (which is much more supple). Fibro cartilage is will wear away more quickly and the patient may need further surgery later on.
- Autologous chondrocyte implantation (ACI)
This has been the most interesting invention in the field of cartilage repair. A small piece of cartilage is taken from, for example, the knee (biopsy) and sent to a laboratory which grows morecartilage cells from the sample. About six weeks later the new cartilage cells are implanted into the knee. A piece of outer layer of bone from the lower leg (periosteum) is taken and sewn into the area of cartilage damage. The cartilage cells that were cultivated in the lab are then injected into that area and the periosteum is sealed – the cartilage then grows back.
Cartilage from undamaged areas of the joint is moved to the damaged area. The cartilage that is moved has to be in a non-weight-bearing part of the joint. This procedure is not suitable when there is widespread damage, as in osteoarthritis. This treatment is only recommended for isolated areas of cartilage damage, generally limited to 10-20mm in size, most commonly found in patients under the age of 50 years who experienced a trauma in the affected area.