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Knee Cartilage Repair: How Cartilage Injuries Are Like Potholes

James L. Carey, MD, MPH

Imagine driving along a busy four-lane highway after a harsh winter. High traffic, snowplows and salt trucks were constant for weeks on end. Now that warmer weather has arrived, all that remains are potholes.

This is basically what happens when you injure the cartilage in your knee, says James L. Carey, MD, MPH, Director of the Penn Cartilage Center.

Cartilage is the shiny surface that coats our bones and allows them to glide at the joints. It requires repair after damage, much like roads after long periods of abuse. Cartilage on cartilage is 1,000 times more slippery than ice on ice.

Dr. Carey explains the similarities between knee cartilage injuries and potholes, and what the road to repair looks like.

Some are minor, some are major

Not all potholes are equal. The same goes for cartilage injuries. There are two types: a focal defect and a regional defect. And each requires a different treatment course.

“When there’s a focal defect, like a small pothole on a good road, we can repair it,” Dr. Carey says. “But when the defect is regional, where all of the cartilage is lost on the surface, the joint gets replaced, like a total road resurfacing. They are kind of on a continuum because little potholes can turn a street into a bad road.”

Damage occurs over time

Just as potholes do not appear overnight, cartilage injuries take time to develop. This process is called repetitive microtrauma.

Simply going up and down stairs over and over again can lead to wear and tear of cartilage,” Dr. Carey says. “You may experience discomfort here and there. But, over time, it becomes painful all the time.”

“Sometimes, it’s not until there’s a loose piece of cartilage - or the pothole is totally uncovered - that you become symptomatic,” Dr. Carey adds.

One condition caused by microtrauma is osteochondritis dissecans, where part of the cartilage or bone separates from the knee.

Treating knee cartilage injuries is important

The same rule applies to cartilage injuries. “As the lesions in cartilage get larger in size, the outcomes from treatment become less predictable,” Dr. Carey says.

Unfortunately, along with less predictability comes a host of problems.

As Dr. Carey explains, cartilage damage can limit a person’s motion to the point where the knee cannot bend or straighten completely. Or during movement, a person will have “catching sensations—where motion of the knee is temporarily inhibited—or locking sensations—where motion of the knee is halted,” he says.

Pain and swelling are common as well. Resting for a week or two can help, but often that’s not a long-term option, he says: “People who play soccer or lacrosse want to continue to play soccer or lacrosse. They don’t want to switch to chess or checkers.”

That’s why early treatment is important. You don’t want to wait too long because you may create more problems down the road.

It’s like driving on a road littered with potholes. You can dodge them as best you can, but you’re bound to blow out a tire eventually.

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