How do I know if I have a metal allergy to the knee part?

Orthopaedic implants are made of alloys of cobalt-chrome and titanium that have been implanted in millions of patients over the past three decades. Allergies to solid metal alloys are sometimes speculated, but are rarely seen in practice. Most instances of a painful knee after replacement have to do with a problem related to the surgery, or possibly an infection. A true metal allergy is extremely rare, and seldom encountered in clinical medicine.

What will weather changes feel like in the knee?

Some patients report increased pain and stiffness or can feel changes in the weather after knee surgery, especially with an artificial joint. These sensations are not common though and usually disappear over one to two years after surgery. For the first couple of years, the bone adapts and grows around the metal prosthesis and this bone activity probably leads to increased sensitivity to weather and pressure changes that some patients can feel in their joints.

What do I need to know about future dental work and other surgery?

Because you have an artificial knee joint in place, you must take care to protect it from infection. The same applies to any artificial implant in your body. Before having dental work (teeth cleaning, fillings, extraction or root canals) or certain medical procedures (colonoscopy, biopsy, endoscopies, etc.), you must take an antibiotic.

The antibiotic helps prevent bacteria from getting into the blood stream and thus into your knee. The odds of this happening are very rare, but the antibiotic can reduce this already small risk.

For routine dental prophylaxis following knee replacement surgery, antibiotics are required for your lifetime after the surgery.

What antibiotics are used to protect the prosthetic knee joint if I have dental work?

Cephalexin and amoxicillin are antibiotics commonly prescribed before and after dental work. You may take azithromycin or clindamycin if you are allergic to amoxicillin. You also may take any antibiotic recommended by the American Heart Association.

What other situations will I need antibiotics for after the knee replacement?

Antibiotics given for other medical procedures may vary. Contact us for advice if there is any doubt. Keep in mind that it will be necessary for you to be treated with a full course of antibiotics if you develop an infection such as an abscessed tooth, pneumonia, bronchitis, and skin or urinary infections.

If you cut your foot, have broken skin on the leg, or have infection in a toenail after a knee replacement, seek medical attention immediately. Ignoring a festering sore means there is a risk the bacteria could migrate to the knee implant, resulting in a serious deep infection, even though it happens rarely.

Will the knee set off a metal detector at the airport?

Most likely, it will. Tell airport personnel you have an artificial joint before entering the metal detector. Metal detection sensitivity at airports is highly variable and it is impossible to say if a certain detector will set off the equipment. We will supply you with an implant identification card you can carry to prove you have metal knee replacement parts.

Can I have a MRI (magnetic resonance imaging) scan after knee replacement?

Yes, MRI scans of other parts of your body are safe after knee replacement. Although some old MRI scanning equipment may not be compatible with your prosthesis, the majority of MRI scanning equipment today is safe and compatible with knee replacement parts. You may also have a CT (computerized tomography) scan of any part of your body after a knee replacement.

How will I know if my knee implants happen to be recalled?

In the extremely unlikely event of a recalled implant, the company who made the device contacts you. All implants have lot numbers registered with the implant maker. This information is kept in your medical record. If you want a copy of your X-ray or exact implant type and model for your records, please let us know.

Rest assured that of the millions of artificial joints implanted each year, the incidence of recall is exceedingly rare. Implant companies monitor the performance of their products very carefully.

Is there a long-term risk of failure of knee implants?

No, the implants are engineered to withstand your body weight and activity level, but the moving parts of a knee replacement do wear over a period of several decades. A properly aligned knee replacement done by a competent, experienced surgeon usually lasts the lifetime of most patients.

Subtle component mal-positioning and suboptimal orientation can, however, compromise the lifespan of the implant. This is why the skill and expertise with which the knee is implanted in your body is a critical determinant of how long the knee last sand how well it performs.

How many times can you replace a total knee?

With modern technology, cases that were considered hopeless a few years ago can undergo successful knee replacement surgery. Such complex knee replacements are done every week in our specialty practice, and are referred from all over. There is no hard and fast rule as to how many times a knee can be replaced. Knees that have had multiple operations may be missing structural bone support, muscle cover and quadriceps support.

While we hope you never need such complicated knee operations, it is possible to get patients mobile again in situations that would have resulted in an amputation in the past. This reflects advances in surgery techniques and related technology.

Learn more about knee replacement surgery at MU Health Care.