|Wednesday, September 22
Knee cartilage tears are among the most common injuries in athletics, mainly because the knee joint is subject to such constant pounding and torque in so many popular sports, from football and basketball to soccer and hockey. And while a cartilage tear may not be as immediately catastrophic as, say, a torn anterior cruciate ligament, the long-term effects can be more debilitating.
The knee joint contains two types of cartilage: meniscus and articular. Meniscus cartilage is located between the thigh bone (femur) and shin bone (tibia) that serves to cushion and lessen friction at the junction of those two bones, as well as distribute the load and shock of walking and running and provide lubrication for the knee joint. The knee has two sections of meniscus, corresponding to the two rounded condyles at the end of the femur (see illustration below). Articular, or hyaline, cartilage is the slick, durable substance that covers the ends of the femur and tibia and allows the two bones two glide against each other without grinding. Of the two types, meniscus is much more likely to be torn while playing sports, because it's the first line of defense in absorbing trauma in the knee. But either or both types can be damaged by the trauma.
We asked Dr. Jerrald Goldman, team orthopedist for the Oakland A's and a member of the Association of Professional Team Physicians (PTP), to explain the basics of this injury.
What causes a cartilage tear?
Dr. Goldman: A cartilage tear most commonly occurs with the knee bent or flexed as part of a twisting, torquing injury. The meniscus injury was first really described in Scottish coal miners, who were down on their knees doing a lot of pivoting and would get horizontal tears, similar to a piece of plywood delaminating.
Both the meniscus and articular cartilage can get damaged in sports. Frequently in MRI images, we see that not only is there a meniscus tear but there's a bruise that occurred to the articular cartilage and bone underneath. It's very common when there's a torn ACL to have a bruise of the joint surface and the underlying bone as well as a meniscus tear.
What are the symptoms of a cartilage tear?
Dr. Goldman: In sports, the injury often occurs abruptly. The athlete will usually feel something tear. The knee may give away and immediately swells, and there'll be acute pain and difficulty in walking. The ongoing symtpoms include pain along the side of the knee where the meniscus is torn when he twists or flexes his knee or when there's a combination of flexing and twisting. He might have instability as well in which a piece of cartilage actually moves in the joint and gives him the feeling that his knee is going to give.
In the general population, tears of attrition occur particularly as we age -- that is, gradually increasing in discomfort along the joint line, with the pain relating to activity. So an injury can occur over time as well as acutely -- for example, a person who kneels and squats during gardening.
The patient also might hear a clicking sound when the knee moves, but it isn't as common as the sensation that something just gave in the knee. Patients usually have an intuitive feel about their knees; they can tell you that something's not right even if they can't quite describe it.
How are cartilage tears diagnosed?
How are these injuries treated?Dr. Goldman: Usually orthopedic surgeons don't see these patients in the general population right after the injury occurs because they go to a primary-care doctor first and let the knee quiet down. When the symptoms persist, that's when we see them. With pro athletes, we see them right away; it makes the diagnosis quicker.
No matter if you're a professional athlete or a weekend warrior, the first line of treatment is to ice and immobilize the knee and let the symptoms calm down. If we suspect that there is a meniscus tear in a pro athlete, the next step is to get an MRI evaluation, and once that's been done, you have to present to that athlete the choice of playing through the injury or having the meniscus treated surgically.
The surgery option brings up two issues. Some of these tears can be repaired. The good part of the repair is that it extends the longevity of the knee's healthy function. The bad part is that it will take the player out of action for six months minimum. That means that he will miss either an entire season or the rest of the season. Most players don't want to do that. My experience with competitive athletes is that they don't want a repair; they want the torn section of the meniscus removed so they can go back to playing as soon as possible.
The most common procedure with pro athletes is called a menisectomy, which means we take out that portion of the meniscus that's torn. When you read in the newspaper that a player's meniscus has been repaired, most of the time that's not correct. It usually means that a portion of the meniscus was removed so that the knee would be functionally normal, but not anatomically normal. The fact that we can do this procedure arthroscopically saves a lot of recovery time. I've had baseball players back in action is as little as three weeks after a simple menisectomy using an arthroscopic procedure.
If I have an athlete who says he'll give up his season, I'll repair the cartilage if possible. But when you have a pro athlete who has a five- or six-year career, most of the time he won't want to be out of action for the amount of time it will take to recover from a repaired meniscus. When the athlete has a torn ACL that is going to take him out of action for a year anyway, then we absolutely will repair a mensicus at the same time.
In recreational athletes, the goal is meniscus preservation. If I can talk the patient into having a mensicus tear repaired, that's what I'm going to do. If the patient says that he wants to go back to playing soon, it's his choice. All I can try to do is educate the patient. He makes the ultimate decision.
What affects how well the cartilage will heal?
Dr. Goldman: The blood supply to the meniscus is present throughout the outer 25 percent of it. Any tear that is in the substance of the meniscus and isn't located near the connection to the soft tissue won't heal because there's no blood supply to it.
What is rehabilitation like?Dr. Goldman: We rehab patients much earlier than we used to. We are very aggressive on that. The thing that slows rehab down is if the patient has a recurrent swelling in the knee; then you have to back off a bit. You push, push, push with the rehab, and then maybe have to back off. The only way you know how fast the knee can recover is to keep pushing.
What's the long-term prognosis for this injury, and what sort of new treatments are being used?
Dr. Goldman: The bottom line is that you put the articular cartilage at risk when there's a deficit of meniscus cartilage. When the articular cartilage wears out, that's what we commonly call arthritis. When you take out meniscus, you put more load on the articular cartilage, which is more likely to wear out. But there are a lot of variables that make it hard to predict when the knee will become arthritic. For example, it depends on your genetic make-up, how much weight you gain over the years, what sort of sports you take up (such as long-distance running), or whether you have pre-existing injury with some subsurface damage. If you have really good genes and don't damage your knee through repetitive-impact activities, your joint might last as long as it normally would have. Or if you were going to get arthritis at 70, maybe you'll get it at 60. We can only tell people that they're at risk, not exactly what's going to happen with their knee.
Not everybody who has arthritis is symptomatic. If somebody is arthritic, what treatments he needs depends on what his symptoms are and how old he is. If you have a 35-year-old, the likelihood of doing a joint replacement is very small. You're going to try and find other ways to treat the condition if possible. We try to reserve total joint replacement for people in their 60s, not their 20s and 30s.
There are new procedures available for the restoration of articular cartilage -- specifically, the implantation of cartilage tissue grown outside the body (called Carticel) and a procedure in which small plugs of healthy cartilage from non-weightbearing portions of bone are transplanted in place of plugs of damaged cartilage -- but we don't have long-term experience with these procedures. They are best-suited for situations involving a small area of articular cartilage that's abnormal and can be treated. But that sort of situation is not all that frequent. You have to remember that a Carticel procedure involves three separate operations. You have to harvest cartilage, then implant it and cover it with a membrane, and then take out the membrane. Certainly a professional athlete is not going to put up with that prolonged a process.
Can cartilage damage be prevented?Dr. Goldman: When it comes to treatment of cartilage damage, you're talking about a pyramid. The elite athlete is at the top of that pyramid. Torn cartilage injuries occur to all sorts of people. For an athlete this injury has a different meaning. But all patients can help themselves prevent or lessen the impact of torn cartilage. They have to understand that for every pound they gain in excess of normal weight, that translates into three to four additional pounds across the knee. That's very important. If you're 20 pounds overweight, that's 60 to 80 additional pounds that you put across your knee every time you take a step. That kind of load wears the knee out earlier. And people need to be aware that the quadriceps, the four-headed muscle in front of the thigh, is a crucial shock and impact absorber. It's important to keep that muscle strong and flexible, because it will help protect the joint surfaces of the knee. Keeping your weight down and keeping your legs strong are probably the most important of all preventive measures that can be taken.