Minimally-invasive vs. traditional knee replacement, Q & A


Q: I need a knee replacement and am trying to decide between a minimally invasive operation and a traditional one. Which is better?

A.The traditional operation involves an incision that’s about eight to 10 inches long that goes down the front of the knee and leg. With the minimally invasive operation, the incision is about half as long, and some of the operations use a “lateral” approach that involves making the incision on the outside of the knee. But the traditional and the minimally invasive operations have more in common than not. The surgeon still cuts away portions of the femur (thighbone) and the tibia (shin bone) that form the knee, and it still involves replacing them with a prosthesis that is designed to restore movement and decrease pain.

Some people find minimally invasive surgery appealing for cosmetic reasons — and it does result in a smaller scar. But the main selling points are less pain after the operation and a speedier recovery, so the benefits of knee replacement are experienced sooner. Minimally invasive surgery should be able to deliver on these promises: a smaller incision does mean less tissue damage. And proponents of the operations can point to some studies that have shown some advantages, such as shorter hospital stays and less blood loss.

But replacing a knee isn’t like taking out a gall bladder. A device has to be implanted into the body. The jury is still very much out whether replacements done through smaller incisions will last as long and be as stable as those done through the larger incision. As a surgeon who has done thousands of knee replacements the traditional way, I think the view — the direct visualization — that the surgeon gets of the joint through the larger incision is important to proper placement of the prostheses and avoiding surgical complications. And there are other ways to reduce postoperative pain and speed recovery besides making a smaller incision. They range from injections of long-acting painkillers into the joint and surrounding tissues, to cold wraps around the joint, to “constant passive motion” machines that can be used in the days right after surgery to exercise the knee gently, keeping down swelling and stiffness. I don’t think minimally invasive surgery is the kind of “disruptive technology” that is going to revolutionize total knee replacement, which is already a safe, effective, time-tested operation. The gains, if any, are likely to be marginal, and I think these other approaches to postoperative care can probably match them.

A couple of general points about new surgical procedures. Surgeons have learning curves. You don’t want to be a patient on the steep part. It’s important, therefore, to ask how many of these procedures a surgeon has done. And surgical techniques aren’t like medications that go through clinical trials and FDA approvals before they are on the market.

It’s great that there’s innovation. The recovery from knee replacement is painful — and always requires a lot of hard work. Anything that makes it easier for patients is welcome.

But joint replacement is a big money maker that engenders a lot of competition for patients among surgeons and hospitals. Touting minimally invasive surgery before it has proven its value is a way of drumming up business. So my advice to you is pick a skillful surgeon who does a large number of knee replacements, in a hospital that does the same.

— Donald T. Reilly, M.D.

Harvard Health Letter Editorial Board

New England Baptist Hospital, Boston

This Question and Answer first appeared in the May 2008 Harvard Health Letter, available at


If your doctor has recommended knee replacement surgery, one of the goals is to have a smoother and straighter knee. Often, the leg has become bent from the wearing out of the inside or outside of the knee joint. You may notice that you have become knock-kneed where the knees look like they are going to touch together or bow-legged where it looks like you just got off a horse. Either way your doctor can help you straighten your leg with a knee replacement.

Many people think knee replacement surgery involves removing the entire end of your thigh bone (called the femur) and the top of your shin bone (called the tibia) and replacing them with a new hinge. Actually, your doctor will try and save as much of your bones, ligaments and muscles as possible. The new knee will replace only the rough cartilage at the ends of the bones with smooth metal and plastic coverings. This should help ease the pain caused by the bones rubbing during activity or while in bed at night.

Before the Surgery

Once you have made the decision to have knee replacement surgery, your doctor may order some tests to make sure you are healthy enough to have the operation. This may involve blood tests, x-rays, or an electrical picture of your heart called an EKG. There are blood tests to make sure all of the chemicals in your body are working properly. Your doctor may ask you to donate blood before the operation in case it needs to be given back to you after the surgery.

An EKG is done by placing small pads on the front of the chest and hooking up to a machine that creates an electrical picture. There is no pain during the test.

An x-ray is a picture of your lungs to make sure that you are able to breathe well during and after the surgery. Once you have received the pre-surgical clearance for your general health, it is time for your knee replacement surgery.

There are different types of anesthesia that your doctor may recommend. Your doctor may suggest that you go to sleep for the surgery. The anesthesiologist will watch over you very closely while a small tube is placed in your mouth to help you breathe during the operation. Another option is called a spinal. In this case, the lower half of the body is numbed so that you don’t feel anything during the surgery. The anesthesiologist will give you medicine to make you sleepy and not remember the operation. It is important to ask about the risks and benefits of each option.

The Surgery

Let’s go through what actually happens during knee replacement surgery.

Using special instruments, the worn surfaces at the end of the thigh bone or femur (feem-er) are removed. The bone is then shaped to prepare for a new covering that is most commonly made out of metal. Remember, your doctor will only remove enough bone to replace the rough surfaces of your arthritic knee.


The top of the shin bone or tibia is prepared in a similar way. A special instrument is used to remove the worn surface and a new metal tray is placed on top of the remaining bone. This tray holds a special hard plastic spacer that will become the new “shock absorber” between the smooth metal coverings.


As the knee bends, the kneecap rides in a groove at the end of the thighbone. In a healthy knee, that groove is as smooth as ice on ice. When arthritis sets in, the smooth ice becomes rough like sandpaper. Sometimes, the rubbing becomes noisy with popping and clicking. In a knee replacement, a new plastic surface on the back of the knee cap (patella) and the new metal groove at the end of the thigh bone make for a smoother and quieter bending of the knee.

Near the end of your surgery, your surgeon will attach the new metal and plastic coverings to the ends of the bones and the back of the kneecap. This can be done with cement where the new knee is “glued” to the bones.


This can also be done without cement with certain knee implants that can be “press” fit tightly into the bones. Either way, your doctor wants to secure the new knee so you can begin walking as soon as possible!


The incision is then closed up with stitches called sutures (soo-chers). The lining of the knee is stitched back together the same way it was found at the beginning of the surgery. The skin is then closed with sutures or surgical staples depending on your doctor’s choice. To help keep the blood from collecting, some doctors put a small tube in the knee called a drain. You may see this coming from your clean dressing following the surgery. It is usually removed by your doctor or nurse a day or two after the surgery.

After the Surgery in the Hospital

Your doctor will work with you to determine how soon after knee replacement surgery you will be able to bend and move your knee. You will be helped in and out of bed until you feel safe to do it on your own. Physical therapy will be very important after surgery to regain the motion and strength in the new knee. Pain medication will be provided to help make these tasks easier. Over the next few days, usually your diet and bathroom habits will become more normal. The nurses will begin to disconnect you from all the tubes as you eat and walk better.

It is also normal to have a low-grade fever for a few days after surgery. You can help get rid of the fever by taking deep breaths and getting moving. The fevers will usually go away before or just after you leave the hospital. Most patients will leave the hospital after a three to four day stay.

Leaving the Hospital

Now it is time to leave the hospital. Your doctor will help you decide the best place for you to continue to get better and more active. This may be at home or in a rehabilitation (rehab) center. A rehab center is similar to a hospital where you stay there day and night and are cared for by doctors, nurses and therapists. Usually you can stay there until you become well enough to go home.

If your doctor wants you to go home, therapy will continue there as well. The important thing is to make sure the knee is getting all the way straight and as far bent as possible. The stitches or staples in the skin will usually be taken out 10-14 days after surgery. If staples are used, a special tool will help remove them so it is not too painful. Pain medicine will help you tolerate the return home and the exercises needed to make the new knee a success. It is also very important to listen to your doctor’s instructions about returning to work or activity.

There are some symptoms you can watch for after surgery. If the calf begins to look red, hot, or swollen, and is painful to the touch, this may be the beginning of a blood clot. It is important to seek medical attention immediately if you experience these symptoms. After the surgery, any unusual swelling, redness, warmth or draining of fluid from the knee, especially if you are having fevers, should be reported to your doctor.

Over the next several years, your doctor may ask you to take antibiotics before and after any small or large procedure to prevent an infection. This may include simple teeth cleanings. Even though the risk of infection is small after knee replacement, it is important to take all the necessary precautions to prevent one.

For more complete information about knee replacement surgery, visit .

A long-tailed macaque monkey looks for fish in a river in Lesan, East Kalimantan, Indonesia, in Sept. 2007. Long-tailed macaque monkeys have a reputation for knowing how to find food, whether it be grabbing fruit from jungle trees or snatching a banana from a startled tourist. Now, researchers say they have discovered groups of the silver-haired monkeys in Indonesia that fish.
(AP Photo/Mel White)

By Michael Casey, 06.10.08,, BANGKOK, Thailand – Long-tailed macaque monkeys have a reputation for knowing how to find food – whether it be grabbing fruit from jungle trees or snatching a banana from a startled tourist.

Now, researchers say they have discovered groups of the silver-haired monkeys in Indonesia that fish.

Groups of long-tailed macaques were observed four times over the past eight years scooping up small fish with their hands and eating them along rivers in East Kalimantan and North Sumatra provinces, according to researchers from The Nature Conservancy and the Great Ape Trust.

The species had been known to eat fruit and forage for crabs and insects, but never before fish from rivers.

“It’s exciting that after such a long time you see new behavior,” said Erik Meijaard, one of the authors of a study on fishing macaques that appeared in last month’s International Journal of Primatology. “It’s an indication of how little we know about the species.”

Meijaard, a senior science adviser at The Nature Conservancy, said it was unclear what prompted the long-tailed macaques to go fishing. But he said it showed a side of the monkeys that is well-known to researchers – an ability to adapt to the changing environment and shifting food sources.

“They are a survivor species, which has the knowledge to cope with difficult conditions,” Meijaard said Tuesday. “This behavior potentially symbolizes that ecological flexibility.”

The other authors of the paper, which describes the fishing as “rare and isolated” behavior, are The Nature Conservancy volunteers Anne-Marie E. Stewart, Chris H. Gordon and Philippa Schroor, and Serge Wich of the Great Ape Trust.

Some other primates have exhibited fishing behavior, Meijaard wrote, including Japanese macaques, chacma baboons, olive baboons, chimpanzees and orangutans.

Agustin Fuentes, a University of Notre Dame anthropology professor who studies long-tailed macaques, or macaca fascicularis, on the Indonesian island of Bali and in Singapore, said he was “heartened” to see the finding published because such details can offer insight into the “complexity of these animals.”

“It was not surprising to me because they are very adaptive,” he said. “If you provide them with an opportunity to get something tasty, they will do their best to get it.”

Fuentes, who is not connected with the published study, said he has seen similar behavior in Bali, where he has observed long-tailed macaques in flooded paddy fields foraging for frogs and crabs. He said it affirms his belief that their ability to thrive in urban and rural environments from Indonesia to northern Thailand could offer lessons for endangered species.

“We look at so many primate species not doing well. But at the same time, these macaques are doing very well,” he said. “We should learn what they do successfully in relation to other species.”

Still, Fuentes and Meijaard said further research was needed to understand the full significance of the behavior. Among the lingering questions are what prompted the monkeys to go fishing and how common it is among the species.

Long-tailed macaques were twice observed catching fish by The Nature Conservancy researchers in 2007, and Wich spotted them doing it two times in 1998 while studying orangutans.

Vulnerable species … the long-tailed macaque.

Longtailed Macaque

Distinguishing Characteristics

The body of longtailed macaques varies from gray to reddish brown, with lighter underparts. The hair on the crown of the head grows directly backward, often resulting in a pointed crest. The face is pinkish. Males have cheek whiskers and a mustache; females have a beard. Infants are born black

Physical Characteristics

Head and body length
– Male: 385-503mm (15.2-19.8in)
– Female: 412-648mm (16.2-25.5in)
– Male: 2.5-5.7kg (5.5-12.6lb)
– Female: 4.7-8.3kg (10.4-18.3lb)


Southern Indochina, Burma, Indonesia, Philippines

Primary, secondary, coastal, mangrove, swamp, and riverine forest up to 2000m (6562ft). These macaques are tolerant of humans and may be found near villages.


Fruit, 64%; seeds, buds, leaves, other plant parts, and animal prey such as insects, frogs, and crabs. These macaques can be crop raiders.


Diurnal and arboreal. Longtailed macaques swim well and jump into water from nearby trees. The male dominance hierachy is less marked than in other macaques. High-ranking individuals lead the group. Tension after an aggressive interaction is indicated by increased levels of self-grooming, body shaking, and scratching. Tension-reducing reconciliation between individuals consists of the dominant one approaching with raised eye brows, while the opponent stares into the eye of the dominant, lip smacks, and touches the other’s genitals.

Picture Title: Long-tailed macaque (Macaca fascicularis)
Image Location: Ubud, Bali
Photographer/Camera: Photo taken by Rhett A. Butler using a Canon Digital Rebel XT