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Knee Replacement FAQs: The Arthritic Knee

What is arthritis?

In the simplest terms, arthritis is a loss of the articular cartilage inside the joint. The surfaces of the knee joint are covered with the articular cartilage (what one of my friends has described as God’s perfect sponge). Because of repeated injury and wear and tear over time, the articular cartilage is lost, the joint narrows and becomes more and more inflamed.

Why does my knee pain change and why is it so unpredictable?

There are many nerves that go to the knee and up and down the leg. In fact, one nerve, the saphenous nerve, has small branches up and down the entire leg. When the areas innervated by the saphenous are irritated, the pain can present in the shin, behind the knee, in front of the knee and even down into the ankle. There are other nerves that go around the joint and come up in the back of the knee and can cause pain in the thigh and even down to the calf. Furthermore, different areas of the knee have different nerve supplies. Depending on which part of the knee is irritated at any given time, the knee pain can be felt in any number of places.

Is ankle swelling related to my knee arthritis?

Yes, indeed. The fluid around the ankle usually is lymphatic fluid, which is squeezed out of the blood vessel into the cells where the blood vessels don’t reach. Lymphatic fluid is returned to the heart by the lymph system, a very low pressure system that relies on muscle action. When the knee swells it can obstruct the lymphatic vessels that run along the inside part of the knee, acting much like a dam obstruction a stream.

Can a bad knee make my back or hip hurt?

Yes. The legs are part of a large horseshoe-shaped mechanical chain that extends from the bottom of one foot, up the leg, through the pelvis and back down through the other leg and the bottom of the other foot. Anything along this mechanical chain that malfunctions, such as the knee, can affect any other structure that is part of the chain. Therefore, the hip can hurt, especially the opposite side, from a bad knee. The low back is attached to the pelvis, which is part of the mechanical chain; when one knee is bad, the leg shortens and causes a limp. Then the back can hurt because you lean away from the bad knee in order to cause less pressure on it.

Why am I getting more bow-legged or knock-kneed?

The inside and outside knee joint spaces are normally covered by equally thick articular cartilage. Because of the way we’re made, the inside of the knee tends to wear out first (although in some people the outside of the knee can wear out first). If one side of the knee wears out faster than the other side, the foot will drift to that side. If the outside compartment wears out first you become more knock-kneed. If the inside wears down (which is more common) the feet will get closer together, the knees will get further apart and you will be bow-legged.

What can I do to help the pain?

An age-old question and one of the most difficult to address. The sources of pain in the knee, as we discussed above, are many. Anything you can do to keep the knee from swelling will tend to make it function better. Thigh muscles don’t work as effectively when the knee is swollen. It is also very important to stay flexible (the body tends to tighten up as we age). Any sort of stretching exercises are good as long as they don’t leave the muscle excessively sore. (One exercise we restrict our patients from is the leg extension with weights; this exercise is mechanically unsound for the kneecap). Avoiding repetitive motions and pounding of the knee are also extremely important. I would especially recommend that anyone who has a known arthritic knee avoid running. One of my friends on the West Coast once compared the knee to the transmission in an automobile. He observed that putting too big an engine with your car’s transmission will make it fail. Similarly, significant weight gain will hurt the knee. We recommend the South Beach Diet. It is beneficial to your heart, good for your blood sugar and helps you keep weight down.

A pound lost is 4800 saved...take a load off: in a study of 142 overweight men and women with osteoarthritis of the knee, researchers found that every pound patients lost equaled 4 fewer pounds of pressure on their knees.That’s per step; dropping just 10 pounds could spare each knee 48,000 pounds of pressure per mile, says Stephen Messier PhD, study author and an exercise science professor at Wake Forest University. People with osteoarthritis often avoid exercise. But this research shows that exercise and a little weight loss can reduce pain by 30%. PREVENTION MAGAZINE – August ’06 issue

I’ve heard of glucosamine/chondroitin and MSM. Do they work?

Yes, they do. Glucosamine/chondroitin, in multiple studies, have been shown to be as effective in reducing pain as Ibuprofen. MSM also shows promise as a pain reliever. By the way, neither of these compounds has ever been shown to restore the joint cartilage but they act in a way similar to anti inflammatory medications. We currently recommend the CVS or WalMart brands of glucosamine chondroitin (they also happen to be some of the least expensive). Be sure you take a multi-vitamin with magnesium to help the absorption of the chondroitin.

What anti-inflammatory medicines do you recommend?

I personally take aspirin (I’m allergic to a lot of the anti-inflammatory medications). Ibuprofen and Naproxen still are quite good, although Naproxen has recently been shown to have increased heart risk in some people. Be sure you drink plenty of fluids when you take any of these medicines. In the national meetings Naproxen (or the lesser strength brand name Aleve) is the current best recommendation. Arthritis Strength Tylenol is also a good choice if you don’t have liver disease. Some of the more expensive, newest generation anti-inflammatory medications have not lived up to expectations and can be quite pricey. You can buy two or three months supply of Naproxen at discount warehouses for about $8.

My family doctor recommened synthetic joint fluid (e.g. Synvisc or Hytropan) injection. How do you feel about these?

I’m less than enthusiastic about them. The most promising candidate for receiving the synthetic joint fluid injection (such as Synvisc or Hyalgan) is someone who still has cartilage left. The mechanism action of these compounds is to stabilize cartilage that is still present. Once you’ve lost all of your cartilage and have bone on bone changes, I don’t believe that these medications have much to offer for many people.

Can you give me a shot to make my knee feel better?

Certainly. We use a combination of Depo-Medrol, which is a super strong cortisone, along with local anesthetics, on a routine basis, for people who are having to postpone knee replacement for social or family issues. We can give these injections at intervals of 6 weeks to 3 months depending on the amount of inflammation. There is a limit to the number of these injections we can give. They will usually work for some number of months. Eventually the injections quit working at which point knee replacement (or arthroplasty as it’s known in medical circles) becomes more viable.

I’ve already had x-rays and an MRI. Why are you taking more x-rays?

The knee is a weight bearing joint and most people we see have not had a weight bearing x-ray. Multiple studies have shown that the knee wears out first in the area where the knee is in the middle part of bending. Therefore we take a mid-flexion weight bearing x-ray. We also take an x-ray with the knee out straight in weight bearing to see if the knee is worn in a different place. These x-rays help us decide the best approach to the surgery. We make notes in your chart as to whether you’re varus (bow-legged) or valgus (knock kneed) in order to gauge preoperatively the surgical approach. The MRI is quite good at detecting cartilage tears. In tact, very few people with arthritis don’t have a cartilage tear. MRIs are not done in a w3eight bearing position and therefore are not as helpful.

My doctor told me I have a torn knee cartilage but you say it’s arthritis. How can that be?

See the above question. As the articular cartilage wears down, the meniscus cartilage can either be torn or displaced. The meniscus cartilage (which feels fibrous like your ear or nose) serves as a pad between the two articular cartilages. The articular cartilage (the spongy cartilage) wears off roughly. As a result, the meniscus will often be torn because of the rough edges. One of the reasons we shoot the weight-bearing x-ray is to be sure that the knee isn’t already down to bone on bone, irrespective of what the MRI report says. There have been several studies done that show performing arthroscopy on people with bone on bone changes on a weight bearing x-rays is ineffective. Therefore we don’t offer it. And as I noted abut the Synvisc injections — once bone on bone occurs, it tends to be very ineffective. So, your doctor may be absolutely correct that you have a torn knee cartilage but that might not be the only problem.

I had a fall onto my knee years ago. Could that have caused arthritis?

It certainly could. Furthermore, working on concrete floors is associated with knee arthritis (as is a strong family history). When you crack the articular cartilage in the knee by a mishap such as a fall or a jump from a height, this articular cartilage "sponge" can only absorb so much. Once the cartilage cracks, its mechanical properties are completely and irreversibly changed, leading to premature wear.

Can any of my daily medicines make my joints ache?

Yes, they can. We found that some of the anti-cholesterol drugs such as Lipitor are strongly associated with multiple joint aches. Furthermore, if you develop an allergy to a medicine, sometimes the immune system will deposit chemical in the joint. That’s one reason we ask for a history of drug allergies as well as a list of medications you currently take.

I have Fibromyalgia. Does that make recovery from knee surgery more difficult?

It can. The diagnosis of fibromyalgia seems to be a very common one these days. A friend, who is a specialist in this area, has very strict criteria for diagnosing fibromyalgia. If indeed you are accurately diagnosed, the joint will tend to be stiffer and recovery will be a bit slower. However, we have seen patients with fibromyalgia make complete recoveries. Knee replacement also tends to make the other joints a little more stiff. General muscle aches occur because of the alteration that has to occur in the way you walk.

Can’t you simply do arthroscopy to treat the arthritis?

The answer is a general no. Arthroscopy has very little to offer in the definitive treatment of arthritis (unless someone is having locking or catching or the knee getting stuck). The weight bearing x-rays help us decide who would not benefit from an arthroscopy. There again, there have been multiple studies that show knee arthritis with arthroscopy is relatively ineffective in the long run. We don’t want to do a surgery on you that’s not going to work. Occasionally, we will do arthroscopy on someone who is younger and is willing to try anything (short of a knee replacement) for some temporary relief. At the age of 52, if my knee locks and aches and I find out I have arthritis, I probably would have arthroscopy first, but I know the risks and the likelihood of failure or success. The other downside to arthroscopy is that sometimes when the knee is inflamed, simply putting a small hole under the knee to insert the arthroscope, can irritate the knee and make the knee worse.

I only have pain in one part of my knee. Do you perform partial knee replacements?

We certainly do. In fact, partial knee replacements currently comprise about 10% of my knee replacement practice. We’re very strict in our criteria for who can have a partial knee replacement. The patient’s pain has to be only in one compartment. There has to be either no kneecap type pain or kneecap pain that seems to be muscle strain related. These partial knee replacements function very well and last as long as regular knee replacements in studies from Europe. They also carry a lower risk and have a greater functional capacity than do complete knee replacements.

I’ve had three major knee surgeries before. Does that make knee replacement more difficult to perform?

As a rule, yes. A great deal of scarring occurs with each knee surgery (especially if the surgery was done long ago when casts were placed post operatively). Incisions in different places can also make the surgery more difficult. However, in some cases, people who have had multiple knee surgeries can recover more quickly because they have more realistic expectations in the post operative period.

An article in a magazine I read talked about a new technique called "minimally invasive knee replacement." What is it and do you perform it?

A minimally invasive procedure means using a smaller incision and different techniques to replace the knee. We perform minimally invasive knee replacement almost exclusively. We’ve found that the minimally invasive technique hurts less and generally results in a more rapid recovery time. In a nutshell, the minimally invasive technique involves handling the kneecap differently, using different retractors and using a natural progression of the replacement to keep the incision small. My smallest incision is 4 inches and the largest one, depending on the size of the knee, is anywhere from 5 - 6 inches. Around the country most knee replacement surgery is done through a 10-12 inch incision.

How many knee replacements do you do?

I do about 175 knee replacements a year (approximately 1500 during my medical career). We do either 5 or 6 knee replacement surgeries every Monday. I’m a member of multiple medical specialty societies and attempt to stay abreast of the current developments including advances in minimally invasive and computer guided surgery. There are exciting developments on the horizon but the knee replacements we are doing right now function very well.

BONUS: Do you operate anywhere besides St. Vincent’s.