Joint replacement

 | September 1, 2006

Joint replacement

Joint replacement is nothing new. Experiments with arthroplasty (replacement of all or part of a joint) were under way as early as the 1930s. These efforts stalled because of major complications: serious infections, problems attaching the replacement joint, and lack of durable materials. By the late 1960s, technology provided solutions. Doctors were able to protect against infection by using antibiotics, and surgeons began using dental cement to secure joints made from new materials such as titanium, cobalt-chrome alloy, and high-density polyethylene, which are lightweight and strong enough to withstand years of wear.

Thanks to improved materials, better sizing, and precision surgical tools, the success rate for knee and hip replacement surgery is now 90% to 95%. About 220,000 total hip replacements and 418,000 total knee replacements are performed in the United States each year. Newer procedures including knee and hip resurfacing are also becoming available.

Still, people need to have realistic expectations about what joint replacement surgery can and cannot do. It's true that Jack Nicklaus returned to tournament golf after his hip replacement. But although your hip or knee replacement should allow you to engage in normal activities for your age, it won't enable you to run marathons, ski on moguls, or do more than you could before you became disabled. And joint replacement doesn't guarantee that you will be able to move or use the joint normally. Particularly at first, you will need to limit your range of motion to avoid dislocating the new joint. Many patients find the recovery period painful. Still, patients who are willing and able to participate in physical therapy can experience great improvement in function. The major consistent benefit is substantial relief from pain — after you've healed from the surgery. Full recovery takes about three months.

Like a pair of shoes, an artificial joint has a limited life span. The more demand your activities place on the new joint, the quicker it will wear out. With normal activity, most last 15–20 years. If you do regular high-impact exercise, your implant won't last as long. If possible, people under 60 are encouraged to delay the procedure because it is more likely that they will need later surgery to replace the implant — particularly if they are extremely active or overweight. Surgery to replace an implant, called revision surgery, is more difficult because there is less bone to work with after removing the first implant.

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Choices in joint replacement

Work with your doctor to decide whether replacing your knee or hip joint is a good solution for you. Once you have answered that question, you'll need to make other decisions, including who will do the procedure, where to have it done, what type of implant to have, whether to replace one or two joints, and whether to do them both at once or one at a time.

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Do you need a new joint?

When is it time for a joint replacement? Joint replacement is always an elective procedure. A doctor may recommend it, but you must weigh the benefits and risks and come to your own decision about whether, or when, to undergo this major surgery. Although your age is an important factor, the decision to have a joint replacement is based on your disability — how much pain you're in and how much your joint problems limit your activities. It may be time to consider knee or hip replacement if one or more of the following apply to you.

You are unable to complete normal daily tasks without help.

You have significant pain every day.

Pain keeps you awake at night despite the use of medications.

Nonsurgical approaches — such as medications, the use of a cane, and diligent physical therapy — have not relieved your pain.

Less complicated surgical procedures are unlikely to help.

Pain keeps you from walking or bending over.

Pain doesn't subside when you rest.

You can't bend or straighten your knee, or your hip is so stiff that you can't lift your leg.

You are suffering severe side effects from the medications needed to control your joint symptoms.

X-rays show advanced arthritis or other damage.

It is possible to wait too long. According to a study by Canadian researchers, waiting until joint problems have severely limited your function may lessen the benefit you get from knee or hip replacement. Two years after surgery, people who had waited longer had less pain relief and were five times as likely to need assistance with basic self-care activities. Taking into account the condition of your joints, your age, and your overall health, you and your doctor need to strike a balance between operating too soon (increasing the chance that the replacement joint will wear out) and waiting too long (meaning you will get less benefit from the procedure).

The average age for total knee replacement is 67; for total hip replacement it's 65. Advancing age isn't necessarily an impediment. In studies from Canada and Chicago, patients 80 and older improved their function just as much and experienced no more pain after knee or hip replacement than patients ages 50–79. Still, some people are not good candidates. A surgeon is unlikely to offer you joint replacement if you have any of these problems:

systemic infection or infection in the damaged knee or hip

leg circulation so poor that it will interfere with healing

severely damaged or nonworking knee muscles or ligaments

severely damaged nerves in the legs

neuromuscular disease such as multiple sclerosis, Parkinson's disease, or stroke

allergy to metal or plastic

medical illness that makes any major surgery risky.

As you make the decision, bear in mind that joint replacement is a major surgery and has a small but real risk of serious complications such as infection, blood clot, and heart attack. According to a large 2005 study, the mortality rate for patients who have total knee replacement surgery is 0.7% during the three months after surgery. The rate for patients who have revision surgery is 1.1%.

One man's story: Reflections on knee replacement John, a 52-year-old accountant, had his right knee replaced. Here, he shares his experience. Why I needed surgery Twenty-five years ago I wrenched my right knee playing racquetball. After that I developed arthritis and I always had some pain. I had a couple of arthroscopic surgeries, but they didn't make much difference. Each year the pain got worse, until it got to where it really hurt to walk down a hill. Whenever I was active, my knee would swell up. My left knee started to hurt, too. Making the decision I wanted to wait as long as possible to have surgery. My doctor never pushed it. He said, "You'll know when it's time." When it got hard just getting up from a chair — it took me 10 steps to get going — I was ready. The surgery There was no pain during surgery. … I remember being awake through most of it and talking to the doctor a few times. Afterward, they put my leg into the CPM machine (a device that bends and strengthens the knee). Postoperative pain I went home after four days. The worst pain was on the ride home. I was taking oxycodone, but I guess it hadn't kicked in yet. I don't know why — maybe it was the motion of the vehicle or the bumpy roads — but the pain was horrendous. I was literally sweating. After that, the pain would come and go but it wasn't too bad. I took oxycodone for about a month. Gradually I got to where I only took it at night and then I stopped altogether. Recovery A physical therapist came over three times a week and helped me do exercises. We'd also measure the angle I could bend my knee from a sitting position. As long as the angle was improving, I knew I was making progress. After about five weeks, I started going back to the office, on crutches, for a few hours a day. Another milestone was when I got to where I could use the stationary bike. One year later I think it's the best thing I ever did. I can play 18 holes of golf without any pain. And not only is my right knee OK, but the left knee that had started to bother me is fine, too.

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Selecting your health care team

Joint replacement is complex surgery, and finding the right surgeon and hospital can make a big difference in your outcome. In general, you're likely to have a better result and fewer complications if your surgeon performs the operation frequently (at least 100 times per year) and operates in a hospital where replacements are commonplace. Make sure to ask the surgeon these questions, and don't be surprised if this rules out the most convenient hospital.

Your orthopedist, rheumatologist, primary care physician, or a friend who has undergone successful joint replacement may recommend a surgeon. Keep in mind that your insurer may restrict you to certain specialists or require a larger co-payment if you go outside your plan.

When you meet for an initial consultation, the surgeon reassesses your condition and works with you to recommend the most appropriate treatment. If it's clear that joint replacement is a good choice, ask these questions to help decide whether this is the right doctor:

Are you board-certified in orthopedic surgery?

How often do you perform this surgery?

What kind of results would you expect for someone in my condition?

May I speak with any of your patients who have had this surgery?

What complications occur most frequently, and how do you deal with them?

Do you usually work with a particular physical therapist or rehabilitation center?

Before undergoing joint replacement, make sure you feel confident that your surgeon has the technical expertise to perform the surgery well and the medical and personal skills to deal with complications and help you get back on your feet afterward.

Much of your experience in the hospital and afterward will center on physical therapy, so it is worth your while to investigate this ahead of time. Look for a physical therapist who is used to working with joint replacement patients. A good physical therapist or rehabilitation center individualizes your rehab program in consultation with your doctor, finds ways you can gain muscle strength even while joint damage limits your activity, helps keep you going even through some discomfort, and helps you reach your goals (whether just walking comfortably or returning to a favorite sport).

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Type of implant

The implant design — there are dozens of them — will depend on your weight, bone quality, age, occupation, and activity level, as well as the surgeon's experience with a particular model or brand. The components of the artificial joint are usually hard polished metal and tough slick plastic, ensuring the smoothest movement and the least wear. The metal parts are titanium-based or a cobalt/chromium-based alloy. The plastic parts are ultra-high-density polyethylene. Some hip replacements now use ceramic in place of some metal parts; so-called "ceramic on ceramic" hip replacements are twice as expensive as conventional "metal on plastic" implants, and it's not yet known whether they offer any long-term advantages.

While some designs have been around for decades and others are brand new, newer is not necessarily better. It takes years to determine whether a new model lasts as long as those with a long-term track record. In some designs that initially seemed promising, problems became apparent only after several years.

Cemented or cementless? You and your surgeon will have a choice of using an implant that is cemented in place or one that is designed to stay put without cement.

Cemented implants use acrylic cement to quickly establish a solid attachment, allowing you to get back on your feet more quickly than cementless implants. Cemented joint replacements have been used successfully for many years and may last more than 20 years. Over time the cement sometimes cracks or wears out, however, loosening the connection between the implant and adjacent bone. If that occurs, you may feel pain as the implant rubs against the bone and wears it away. Eventually, you'll need revision surgery.

For this reason, some surgeons now use cementless implants. Their surfaces are semi-porous, allowing bone to grow into the implant and form a solid attachment that is less likely to loosen. Although cementless implants are held in place with surgical screws or pegs, they are not as secure as cemented models until bone healing occurs, so your doctor may not allow you to put full weight on the leg for six weeks. Despite early hopes that cementless implants would be more durable than cemented implants, some follow-up studies have shown the cementless models have no greater longevity than cemented ones. In evaluating cementless knee prostheses, doctors have found that better attachment to the bone occurs with the thighbone (femur) than with the kneecap or lower leg (tibia). Accordingly, some doctors use a cementless attachment to the femur and cement the other portions of the implant, an approach called hybrid or mixed total knee replacement. In a hybrid hip replacement, the stem of the implant is cemented into the shaft of the thighbone, while a cementless implant is used on the socket.

You are more likely to be offered a cementless implant if you are younger and more active. When younger, bone is stronger and more readily grows into the implant, creating better fixation of the implant. You can discuss your options and preferences for implant attachment with your surgeon, but it's up to the surgeon to make the final decision after assessing the condition of your bone during surgery.

Fixed-bearing versus rotating platform for knee implants. In a fixed-bearing knee prosthesis — the most common type — the tibial component of the prosthesis is topped with a flat metal piece that securely holds a polyethylene insert. When the knee is in motion, the femoral component glides across the polyethylene. In a rotating platform knee prosthesis, the polyethylene insert can rotate slightly, theoretically lessening stress and wear on the implant and improving movement.

Studies comparing the two types of knee replacements have offered mixed results. In 2005, a two-year study in Germany found the rotating platform offered better mobility, while a six-year study in India found no differences between the two types in function, but that the rotating platform was more likely to require revision surgery.

Alarming After knee or hip replacement, your implant is likely to set off a security alarm at an airport or building entrance. In the past, you could show a certificate from your doctor to show you had an implant. Since the Sept. 11, 2001, attacks, security personnel now often ask you to step to the side and show your surgical scar. Then an employee will run a wand over the joint to verify you have an implant.

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Two at once?

If you have severe damage and pain in both knees or hips but are otherwise in good health, you may be able to choose between replacing both joints during a single surgery (simultaneous replacement) or scheduling two separate operations several months apart (staged replacement). The decision requires careful discussion with your doctor and physical therapist. Benefits of a simultaneous approach are a single anesthesia, shorter total hospitalization, and one prolonged rehabilitation that lets you resume normal activities sooner than two shorter ones. You should also consider having simultaneous operations if the condition of your joints is so poor that replacing only one joint would still leave you unable to function during physical therapy, thereby slowing your recovery. In addition, to do well in rehabilitation after simultaneous surgery, you need enough arm strength to cope while you can't stand on either leg.

Having two separate operations requires fewer blood transfusions, and some complications are less likely. In analyzing thousands of knee replacements, Mayo Clinic researchers found that patients who have simultaneous knee replacement are more than twice as likely to develop dangerous blood clots or die within 30 days as patients who have single-knee surgery, although such complications are rare. People over 80 and those with cardiovascular or lung disease are usually offered staged procedures. If you have any significant medical risks, you are probably better off having two separate operations.

Because you spend less time in the hospital, simultaneous joint replacement costs somewhat less than staged procedures. However, as long as both knee replacements are deemed medically necessary, Medicare and most private insurers cover either schedule.

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Partial knee replacement

If your knee damage is limited to one of the bumps on the end of your femur, you may benefit from a partial (unicompartmental) replacement that leaves the rest of the joint intact. This technology has been around for decades, but became more popular once surgeons were able to install the partial implant through a small incision (about 3 inches rather than 8) with minimal impact on muscles and ligaments — a surgery nicknamed the "mini-knee."

The potential advantages are clear: less blood loss, shorter hospitalization, and quicker recovery. However, a unicompartmental replacement lasts only about 10 years. You may be offered this option only if damage is limited to one portion of the knee, if the damage results from a traumatic injury rather than arthritis, and if your ligaments are intact. The ideal patient for this surgery remains an older, thinner person rather than a younger, more active one. It may be suggested to buy time before total knee replacement in someone young and active, however.

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Minimally invasive knee surgery

Minimally invasive knee surgery is an attempt to do replacements through much smaller incisions to limit tissue damage and decrease pain. Despite the benign name, it is still major surgery and the size of the incision depends on the person's size (bigger knees mean bigger incisions). The results from studies comparing minimally invasive surgery to traditional knee replacement vary. Some studies show a higher complication rate with minimally invasive surgery, but in other studies the short-term results are similar to traditional knee replacement.

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Patella resurfacing

In some knee replacements, the kneecap is unaltered, and the artificial implant is shaped to glide easily beneath it. But in another approach, called patellar resurfacing, the surgeon attaches a separate piece to the back of the kneecap to fit smoothly with the implant and resurfaces the patella.

Studies of patella resurfacing have offered varying results: Some find it reduces long-term pain and others find it leads to more complications and a higher failure rate. Some surgeons resurface the patella in most knee replacements; others try to avoid this step unless special circumstances warrant it.

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Hip resurfacing

Hip resurfacing is an alternative to traditional hip replacement. Instead of removing the head of the femur and replacing it with an artificial ball, the head is reshaped and capped with a cobalt prosthetic that fits into a man-made lining in the socket. Resurfacing uses a bigger ball, which some surgeons say makes dislocation less likely and gives the joint the ability to handle greater stress.

The technique was first tried in the 1970s, but it fell out of favor because of problems with the polyethylene parts used at the time. A generation of metal-on-metal caps and socket linings was approved by the FDA in 2006. Some surgeons favor hip resurfacing for younger patients because preserving the top of the femur makes it easier to do subsequent surgery, which becomes more likely in people who will use implants for more than 20 years. Talk with your surgeon about whether this procedure is right for you. Persons with severe bone loss from osteoporosis or other causes are not good candidates for this procedure.

Sign on the dotted knee In rare instances, doctors perform surgery on the wrong limb. An insurance study showed that it happened about 20 times a year in the United States from 1985 through 1995. The two most common mistakes are operating on the wrong leg and operating on the wrong part of the spine. To lower the chances of such an error, the American Academy of Orthopaedic Surgeons has a "sign your site" protocol: Surgeons are supposed to write their initials in indelible ink on the operative site. So if you're having surgery, look for your surgeon's mark. In the unlikely event that it's not there, raise the issue with your surgeon or a nurse.

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Undergoing joint replacement

Joint replacement is usually scheduled several weeks or months in advance. During the weeks preceding the surgery, your health care team will advise you on steps you can take to help ensure a successful outcome. Once the day of surgery arrives, you will follow a standard procedure at your hospital.

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Knee replacement procedure

On the day you're admitted for surgery, you'll meet with an anesthesiologist. Once you're ready for the operation, the anesthesiologist will insert a tube into either a vein or your back, depending on the type of anesthesia to be used. A catheter is inserted into your bladder to remove urine during the surgery. Once you're in the operating room, you will be positioned on your back.

To begin the operation, the orthopedic surgeon makes a cut of about 6–7 inches over your knee. Moving the kneecap out of the way and taking care to do minimal damage to the muscles and ligaments, the surgeon makes flat cuts to remove damaged sections from the top of the tibia and the end of the femur and to carefully contour the bone to fit the implant. Precision guides ensure that the bone is shaped correctly to fit the implant, an innovation that makes knee replacement far more accurate and successful today than in the 1970s. The surgeon then puts trial implants in place and tests to make sure that the knee will straighten and bend without wobbling; it takes great surgical skill to properly balance the ligaments and tendons to work with the implant. The surgeon then attaches the implant components to the femur and tibia with cement or screws (see Figure 12). If your patella will be resurfaced, the surgeon also attaches a small oval-shaped plastic piece to the back. After the surgeon finishes your knee replacement, he or she will stitch your incisions closed.

Figure 12: Total knee replacement The surgeon first cuts away thin slices of bone with damaged cartilage from the end of the femur and the top of the tibia, making sure that the bones are cut to fit precisely the shape of the replacement pieces. The artificial joint is attached to the bones with cement or screws. A small plastic piece goes on the back of the kneecap (patella) to ride smoothly over the other parts of the artificial joint when you bend your knee.

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Hip replacement procedure

Once the tubes that deliver anesthesia are in place, you will be placed on your side. Pillows will help you stay in position during the operation.

The surgeon makes a cut of about 8–12 inches along your hip and separates your thighbone from the hip socket. Using a surgical saw, the surgeon removes the damaged ball at the top of your thighbone; this is measured so a perfectly sized implant can be created from components available in the operating room. The surgeon tunnels down into the femur to create a space for the stem of the implant. After evaluating the quality of bone tissue in your femur, the surgeon decides whether to cement the implant in place. On the socket side of the joint, the surgeon shaves away damaged bone and cartilage and shapes the surface of the bone to hold the socket portion of the implant. After the implant components are prepared, the surgeon secures them in place using cement or screws, or by forcibly press-fitting them in. The surgeon then fits the new ball and socket together and stitches the incision closed (see Figure 13).

Figure 13: Hip replacement surgery When rough and damaged cartilage prevents the bones of the hip from moving smoothly, an orthopedic surgeon can install an artificial joint with two parts. The head of the femur (thighbone) is replaced with an artificial ball with a long stem that fits down inside the femur. An artificial cup fits inside the hip socket. The two pieces fit smoothly together to restore comfortable ball-in-socket movement.

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Recovery in the hospital

Once you recover from the anesthesia in the recovery room, you're moved to a regular room. When you wake up, you'll find several tubes extending from your body — a drain for the surgical area, a catheter to remove urine, and an IV for medications. You will also have elastic stockings or compression devices on your legs to help prevent blood clots. After hip replacement, your operated leg is suspended by a sling or special abduction pillow to keep the hip from dislocating (the ball slipping out of the socket). After knee replacement, your operated leg may be in a splint or in a continuous passive motion (CPM) device that gently bends and straightens the joint by a programmed amount.

Pain control. If you had an anesthesia line in your back, it may be left in place for a day or two to administer medication to keep your lower body pain-free. Otherwise you initially receive pain medication through an IV. If your doctor has recommended patient-controlled anesthesia, you push a button to administer pain-killing drugs into your IV tube as you need them; the machine is programmed so you cannot use too much medication. After a while, you switch to oral painkillers. Don't hesitate to use the medications. Pain is easier to control before it becomes intolerable. Taking medication 30–60 minutes before physical therapy helps you perform the exercises. In addition, the medication can help relieve pain and swelling, particularly after activity.

Breathing. After surgery, small airways in the lungs can collapse and create an ideal environment for pneumonia to develop. To keep your lungs clear, the nurse will instruct you to cough several times an hour and to perform deep breathing exercises. You may be given a breathing exerciser called an incentive spirometer that lets you see how deeply you are breathing and challenges you to expand your lungs fully.

Blood clot prevention. One potential postsurgical danger is the development of a blood clot that travels to the lung, lodging there and blocking off your breathing (pulmonary embolus). To help prevent blood clots, your doctor may place compression devices around your legs and feet. These devices are hooked to a machine that regularly fills them with air to squeeze your calves, forcing blood up your legs to mimic the action that your muscles would provide if you were moving around. Elastic stockings (TED or anti-embolic stockings) worn on both legs keep pressure on your calf muscles (and thereby your legs) to enhance blood flow. A health care professional measures your calves to order the proper size and shows you how to put on the stockings, which can be tricky at first. Blood-thinning medications such as warfarin or heparin may be prescribed for the first several weeks after surgery.

You can help prevent clots by moving around as much as you are allowed. While in bed, increase blood flow by circling your ankles or alternately flexing and pointing your feet. Report any symptoms of a possible leg clot: increasing swelling, pain, tenderness, or redness in your calf. A clot that has reached the lung can cause shortness of breath or chest pain that comes on suddenly with coughing; if this happens, notify your doctor immediately.

Infection control. To prevent infection, patients undergoing joint replacement are routinely given antibiotics for 36–48 hours. Still, it's important to follow your nurse's instructions about cleansing and bandaging your incision. Notify your health professional if you notice these signs of infection: redness, swelling, pain, tenderness, fever, and increasing or odorous drainage. An infection around your incision can usually be treated with antibiotics and scrupulous cleansing and dressing of the wound. In some cases, the surgeon may have to reopen the incision to remove infected tissue. Infections around the incision are taken seriously in order to avoid a deep infection around the prosthesis, which can necessitate removing the implant. This occurs in about 1 in 200 knee or hip replacements.

Steps to restore mobility. Your rehabilitation begins immediately. Grasp the overhead bar to shift around in bed and relieve pressure on your skin. Perform bed exercises as prescribed by your physical therapist.

Before you actively bend a knee replacement, your knee is placed in a CPM machine to bend and straighten it a programmed (and gradually increasing) amount. Use of the CPM device supplements but can't replace your participation in physical therapy.

By the day after surgery, a nurse or physical therapist helps you get out of bed and use crutches or a walker to move to a nearby chair. If you had hip replacement, an abduction pillow between your legs keeps your hips in a safe position while you sit; the first few nights, your leg may be returned to the sling. To prevent your hip from dislocating before the ligaments heal enough to stabilize the area, you must avoid specific movements in the hospital and for several weeks at home (see "After hip surgery: Four tips to avoid dislocation").

After hip surgery: Four tips to avoid dislocation Precautions against dislocating a new hip implant are quite limiting for about six weeks. It's important to follow them regardless of how well you feel, since a position can be risky without causing pain. Bend over as little as possible. Your hip should flex no more than 90 degrees, meaning you should not bend over farther than your waist. This rules out bending over to tie your shoes normally or pick up something you've dropped, and it also means you'll need a raised toilet seat and a chair or bed that is high enough that your knees don't rise above your hips when you sit. Be careful in bed. Lying down, you mustn't pull your knee toward your chest or reach down too far to get your covers. Rely on long-handled gadgets. Four devices can be helpful: a reacher to help you pull up pants or grab items that are out of safe range; a tool to pull on socks without bending over; a shoehorn to put on sturdy non-tying shoes; and a sponge to help you wash below your knees. Avoid movements that turn the operated leg in or out. Keep your feet pointed straight ahead when you sit and stand. Don't cross your legs, even at the ankle. Sleep on your back or on your side with your abduction pillow between your legs.

By the second day, you spend more time sitting up. You walk to the bathroom, and you start rehab exercises with the physical therapist. During the remainder of your hospital stay, you work with the physical therapist in the gym until you achieve certain goals. An occupational therapist or other professional teaches you how to bathe, dress, and get in and out of a car safely without jeopardizing your implant.

The average hospital stay following total knee and hip replacement is four days. Before you can safely go home, you are usually expected to perform the following: get into and out of bed, walk with crutches or a walker, go up and down a curb and the number of steps you must negotiate at home, perform your rehab exercises, and show you can do necessary tasks with little or no assistance (and, after hip replacement, without violating your hip precautions). If you had knee replacement, you should be able to straighten your knee and bend it 90 degrees. Depending on individual circumstances, these requirements may be altered. If you are medically cleared for discharge but not able to do these things, or if you need extra nursing care or have no assistance at home, you are discharged to a rehabilitation center. Many people who live alone choose this option.

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Recovery and rehabilitation

When you first arrive home, you need help — a family member, friend, or person hired to assist with meal preparation, cleaning, bathing, shopping, and just fetching things you need. Depending on your medical condition, a visiting nurse or home health aide may be helpful.

Your degree of participation in a rehabilitation program is a major factor in the success of your implant. Think of yourself as an athlete training to come back from an injury. These first several weeks require much effort. Several times a day, you perform exercises your physical therapist has recommended to restore movement in the joint and strengthen the surrounding muscles (see Figure 14). You can do many of these exercises sitting or lying down. A physical therapist may come to your home or may schedule regular appointments for the first few weeks. In addition to formal exercises, gradually increasing the amount you walk and do normal tasks improves your strength and stamina.

Figure 14: Exercises after knee replacement Under the guidance of your physical therapist you'll gradually be able to do the following exercises: Sitting knee bends: Sit in a chair with a towel under the operated knee. Straighten your knee as far as possible and hold for 5 seconds. Repeat 10 times. Gradually work up to 25 repetitions. Standing knee bends: Hold onto a steady surface such as a table. Bend your operated knee back as far as it will go. Hold for 5 seconds, then lower the leg to the floor. Repeat 10 times. Gradually work up to 25 repetitions.

How long you will need to use crutches or a walker to keep weight off your implant depends on the type of implant you have and individual circumstances. Most people can put a little weight on a cemented implant right away. As postoperative pain decreases, they gradually build to full weight bearing and walking without crutches or a walker by four to six weeks. An uncemented implant isn't secure until bone grows into it; most surgeons will allow you to put only about half your weight on the joint for the first six weeks, after which full weight bearing is allowed. After about six weeks of healing, your rehabilitation goals shift toward restoring your ability to do normal activities, although you may still experience muscle pain and fatigue for several months as your tissues heal.

After six months you should be able to function pretty normally. You can expect to have as much movement as you had before the operation, but without the pain. Just don't expect to have better mobility than you previously had.

Post-surgical pain. Pain is usually well controlled while you're in the hospital, since doctors and nurses are nearby and can provide powerful medications intravenously. Once you return home, the pain level is hard to predict. Some people experience very little and can find relief with ordinary over-the-counter drugs. Others, however, have pain so severe that they describe it as the worst pain of their lives — comparable to childbirth or passing a kidney stone — and are reluctant to even get out of bed.

It's not always clear why a person may experience exceptional pain. It can be a matter of perception — people's threshold for pain varies tremendously. In other cases, there may be an underlying problem causing the pain, such as a swollen tendon or an infection.

The important thing to remember is that you should never suffer in silence. If your pain level is unacceptable, see your surgeon. If there's an underlying cause, he or she can address it. For example, pain caused by a swollen tendon can be alleviated with a steroid shot, and infections can be cured with antibiotics. If there is no direct cause, the surgeon can prescribe a more powerful medication, such as oxycodone (Percocet, OxyContin). This drug is tightly regulated due to its potential for abuse, but it's unlikely to be misused by pain patients and is often effective.

Dos and don'ts These tips can help ensure that your return to mobility following surgery goes smoothly. Don't soak your wound. Upon returning from the hospital, do not soak your wound in water until it has thoroughly sealed and dried. Do eat right. Eating a healthy diet including lots of fruits, vegetables, and whole grains is important to promote proper tissue healing and restore muscle strength. Do learn the signs of blood clots. Warning signs of a leg clot include increasing pain, tenderness, redness, or swelling in your knee and leg. Signs a clot has traveled to your lung include shortness of breath and chest pain that comes on suddenly with coughing. Call your doctor if you develop any of these signs. Don't take risks that could cause you to fall. Be especially careful on stairs until your knee is strong. Use a cane, crutches, or a walker until you have improved your balance and strength. Do look for signs of infection. These include persistent fever, shaking chills, increasing redness or swelling of the knee, drainage from the knee wound, and increasing knee pain with both activity and rest. Do exercise wisely. Performing the exercises your physical therapist recommends is critical for restoring movement in your new joint and strengthening the surrounding muscles.

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Guidelines for recovery from knee replacement

Ask your doctor and physical therapist how soon you can return to specific activities and what preparation will help you achieve those goals.

Driving. If your left knee was replaced and your car is an automatic, you may be able to drive as soon as you are not taking opioid medication and feel up to it. If the right knee was operated on, a wait of six to eight weeks is typical. If pain previously hampered your ability to brake quickly, your reaction time may improve greatly after you have healed.

Work. You'll probably be able to return to a desk job after six to eight weeks; a job requiring lots of standing, walking, or lifting may take twice as long. Avoid heavy lifting, which places significant stress on your implant.

Sex. Wait until the incisions and tissues in the front of the knee heal (about six weeks). If you usually put weight on your knees during sex, you may want to try a position that involves lying on your back or side or even sitting.

Sports. By eight weeks after surgery, you may be able to resume activities such as golfing, bowling, ballroom dancing, biking, swimming, or scuba diving. Some sports will never be advisable with a replacement knee. The prosthesis simply won't hold up to jumping, twisting, or the repeated jarring of running, soccer, basketball, volleyball, or contact sports. However, you may be able to engage in a sport that occasionally requires a brief run, such as gentle doubles tennis. Ask your doctor whether a return to your favorite sport is realistic; if so, your physical therapist can help tailor your rehab program to prepare you for the safest return possible.

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Guidelines for recovery from hip replacement

After hip replacement, your post-op checkup is a good time to clarify what activities are encouraged or prohibited. Some typical guidelines are as follows:

Car travel. Ask the physical therapist for guidance on getting in and out of the car and riding safely. Some vehicles are unacceptably high or low, forcing your hip into an unhealthy position. In some cars, sitting on a firm pillow can help you avoid overflexing your hip. On long drives, stop and get out at least once an hour.

Driving. To drive, you need to be off opioid painkillers and blood thinners, able to put weight on your right leg (for an automatic transmission) or both legs (for a manual transmission), and able to brake without violating your current hip precautions. It usually takes about 6 weeks before you can drive an automatic and 12 weeks for a stick shift.

Sex. Wait until muscles and incisions have healed. You may need to adjust your sexual positions. You might lie on your back or on your non-operated side, resting your operated leg on your partner's leg. Don't flex your hips more than 90 degrees, and don't raise your knees higher than your hips. Avoid positions that rotate your hips out (either sitting or lying with knees wide apart). It may take some time to re-establish or learn new patterns of intimacy, particularly if pain diminished your sex life before surgery.

Work. Depending on the physical demands of your job, it may be three to six months before you can return. If you have a desk job, your chair should have arms and be high enough to properly position your hips.

Sports. Walk as much as you like once you can put weight on your operated leg. Exercise in a warm pool after your incision has closed and the stitches are out. After a few months, you should be able to return to golf (using a cart and not wearing spikes), biking (without steep hills), and ballroom or square dancing. Avoid activities that require jumping or heavy lifting, might jolt or stress your hip, or make it likely you might fall or have something (or someone) bump into your hip. This means that tennis, volleyball, horseback riding, skating, contact sports, soccer, squash, and racquetball are usually out.

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Living with a replacement joint

Eventually, your knee or hip implant may feel like it is truly your own joint. However, complications can occur that shorten the life of an implant, and you may need to take certain precautions.

Infection. Your implant can become infected years after surgery, almost always because infection elsewhere in the body has spread to the area. Seek immediate treatment if you have symptoms of a urinary tract or other infection, and inform all your doctors that you have a joint replacement. At least for the first couple of years, you may be advised to take prophylactic antibiotics before medical procedures that often result in bacteria entering the bloodstream, such as invasive dental work (extractions, gum surgery, root canals, and any cleaning or procedure likely to result in bleeding), a colonoscopy, or any type of surgery. Your doctor can advise you how long to continue these precautions, which are particularly important for those who have an illness or have undergone medical treatment that impairs the immune system.

Leg-length discrepancy. A difference in leg length occurs only rarely after knee replacement but occurs frequently, at least temporarily, after hip replacement. Before surgery, one leg is often shorter than the other — or feels shorter because the joint has deteriorated. Your orthopedic surgeon chooses an implant and plans surgery so that your legs will be equal in length after healing. After hip replacement, muscle weakness or spasm and swelling around the hip may temporarily cause an abnormal tilt to your pelvis and make you feel as though your legs are unequal in length. Stretching and strengthening exercises help restore your pelvis to its proper position (see Figure 15). It may be several months before you can tell if the discrepancy is real and needs to be addressed with the use of a lift in the shoe. When the discrepancy is accompanied by pain, surgery can correct both problems.

Figure 15: Exercises after hip replacement Check with your physical therapist before doing these exercises to strengthen your hip. Standing knee raise: Standing with the aid of a walker or holding a stable surface, lift your thigh to no more than 90° and bend your knee. Hold for 5 to 10 seconds. Straighten your knee and touch the floor with your heel first. Repeat until your leg feels fatigued. Hip abduction: Standing with your hand on a stable surface, lift your leg out to the side as far as you can and hold for 5 to 10 seconds. Keep your hip, knee, and foot pointing straight forward. Repeat until your leg feels fatigued.

Dislocation. In the weeks after a hip replacement, you'll need to take great care to keep from dislocating the implant before the surrounding tissues have healed enough to hold it in place. Even afterward, there is a chance of a painful dislocation. If your hip dislocates, your doctor gives you a sedative while he or she manipulates the implant ball back into the socket. A hip that dislocates more than once usually requires surgery to make the joint more stable.

Loosening. A replacement joint can loosen because the cement never secured it properly or eventually wore out, or because the surrounding bone never grew into the implant to create a tight attachment. This may require revision surgery.

Bone loss. As a joint implant suffers wear and tear, loose particles can be released into the joint. As your immune system attacks these foreign particles, it can also attack surrounding bone, weakening it in a process called osteolysis. This, in turn, may loosen the bone's connection to the implant. Osteolysis is a major factor leading to revision surgery after hip and knee replacement.

More mobility = weight gain Many overweight people who have painful knees or hips anticipate that having a joint replacement will ultimately help them shed weight by helping them be more active. While this expectation seems plausible, in many cases patients actually put on more weight after having surgery. A 2005 study in Orthopedics documented this phenomenon — at least one year following hip or knee replacement surgery, patients gained an average of three pounds, with younger patients adding the most weight. Researchers aren't sure why this occurs — one theory is that increased mobility after surgery leads people to eat out more often and to make more frequent trips to the refrigerator. Whatever the reason, don't assume that joint replacement surgery will automatically help you slim down. To lose weight, you'll need to adhere to a regular exercise program and reduce your total caloric intake.

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Revision surgery

If your implant fails, surgery to replace it takes longer and may be more complicated than your original operation. Look for a surgeon with experience doing both implants and revisions. Before you have revision surgery, your doctor will perform a thorough physical exam. If you're much older than the first time around, you may need to take more precautions. You may be advised to bank extra blood for the lengthy procedure.

During surgery, the surgeon removes the old implant and damaged bone or joint tissue surrounding it. Depending on the amount and condition of the remaining bone tissue, you may need bone repairs or a bone graft to create a stable site for the new implant. Rehabilitation is similar to the initial replacement but takes longer after revision, and the outcome is often inferior. For example, your range of motion in the joint may be more restricted or your leg alignment less even, and even after healing you may need to use a cane to keep full weight off the joint.

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Review Date: 2006-09-01

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