What is Chronic Knee Pain? How do I know if I have it?

Chronic pain has been going on for at least 2 or 3 months without an adequate explanation. Maybe there's an injury in the past--even a long time in the past. But over time, there's been some damage inside the knee joint and then it becomes painful. Why does it become painful? Cartilage is a cushion in all of our joints. In the knee joint, it's about 3/16-inch thick, and it covers, just like a tread, the entire knee surface on the femur side and the tibia side. We in fact have that same cartilage in our knuckles, but in our knuckles, it's only paper thin because we don't walk on our knuckles. If you were to try to walk on our knuckles, it would hurt. So if there was a zone inside the knee joint that becomes damage, even the size of a quarter, then, whenever that piece of the knee joint is bearing the weight, it hurts. If the cartilage is gone, the force is going right to the bone, so it hurts with just about every step you take.

What is cartilage?

Cartilage is so important to our joints. It is about a 3/16-inch coverage over the entire joint surface. For a knee, it'd be all over the femur and all over the tibia, much like a tread of a tire. On the knee, it's about 3/16-inch thick, and in your hand and knuckles, it's only paper thin. Cartilage is made out of a combination of collagen, a strong and complex ropelike molecule, and something called proteoglycan, which is a soupy substance that, when mixed with collagen, makes for a surface that is like slippery leather or vinyl. It's very tough and resilient.

What causes chronic knee pain?

The source of chronic pain in the knee really depends on the circumstances--whether there's an injury in the past, how old you are, and if you have arthritis, it can cause chronic pain. All arthritis is a wearing away of the cartilage surface, either in multiple places in the knee, throughout the entire joint, or perhaps in a young person that's had significant trauma, playing football, soccer, or basketball, where they've had an injury to one spot of the cartilage in their knee. It can be as small as the size of a quarter or a fifty-cent piece. There are many things, depending on what's happened to you, luck, or genes that can cause a loss of cartilage in various places in the knee, which can cause chronic pain.

How is knee pain treated?

When it comes to treatment, specialists start with conservative measures, including anti-inflammatory medication, rest and physical therapy. Sometimes that is enough to significantly improve the situation. If conservative measures don't work, an MRI is usually needed to see joint surface cartilage and ligaments that help hold the knee together. Patients who have large cartilage defects in their knees - similar to craters in the joint's surface - need advanced treatment. Partial or total knee replacements are options that provide long-term relief in relatively older patients. For younger patients, surgeons can now transplant patients' own cartilage back into the defect.

Before a cartilage transplant can occur, surgeons perform a minor surgery so they can take a cartilage biopsy. The biopsy - the size of two small Tic-Tac candies - is from a zone in the knee that does not bear weight. Surgeons then send the biopsy to a lab, where it is cultured and eventually grows into 12 million of the patient's own baby cartilage cells. With these new cells, surgeons open the knee again to clean out the damaged cartilage and replace it with the new. A membrane is sewn around the damaged area to keep the baby cells in place. The cells continue to grow and in about three months, will replace the damaged area.

The best candidates for cartilage transplant are patients in their 20s, 30s and early 40s who do not have arthritis. Patients who are 40s and up can benefit from partial or total knee replacement.

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