If you’re considering a knee replacement—or in fact, a joint replacement of any kind (knee, hip, shoulder, etc.), there’s a very important fact you need to know: Are you allergic to nickel?

 

When a knee joint is surgically replaced, the bottom of the femur (thigh bone) and the top of the tibia (shin bone) are removed and replaced with prostheses. Several types of prostheses exist today and their composition varies. The bearing part of the knee replacement is generally made from polyethylene. The other prosthesis is usually composed of metal. Some are made of a chrome/cobalt alloy, some from stainless steel, some from titanium, and some from a ceramic-coated zirconium known as “oxinium.” The first two contain nickel; the second two do not.

 

 

Several potential allergic reactions to the nickel in the prosthesis can occur, according to a number of articles published in peer-reviewed journals. (Some people, less commonly, are also allergic to cobalt and/or chrome.)

 

First, lymphocytes, patrolling white blood cells that are designed to attack pathogens in the body, can accumulate around the joint and start to dissolve the bone that is in contact with the metal. This can lead to loosening of the prosthesis and sometimes even breakage of the bone.

 

Second, the allergic reaction may cause chronic and unexplained pain in the repaired joint.

 

Third, the patient may experience generalized or localized rashes and eczema in response to the implanted metal.

 

Fourth, although the evidence for this is less solid, some researchers and orthopedic surgeons feel that metal particles that accumulate in the spleen and liver (from wear of the replaced joint over time) can also generate other types of allergic reactions.

 

Although skin-patch tests are not, unfortunately, reliable (false negatives and positives can both occur), anyone considering a knee or hip replacement should get tested for metal allergies before the surgery and any positive reactions taken into consideration. Another possible way to test is to wear nickel-containing jewelry for several weeks before the surgery (using it in a piercing would be the most informative, since the nickel would be in contact with deeper layers of the skin rather than simply the surface) and see if any irritation develops.

 

Most importantly, if you suspect a nickel allergy, you should discuss this with your surgeon at your first consultation. I personally would feel much more comfortable with a surgeon who asks upfront about metal allergies. Prostheses that don’t contain nickel are available, as mentioned above. As the surgeon who performed my husband’s recent knee replacement said, “I would be scared to death to use a nickel-containing prosthesis in a patient with a suspected nickel allergy.” He opted to use an oxinium prosthesis.

 

And this brings me to another important consideration when contemplating a knee or hip replacement: Be sure that the surgeon you choose is open to your asking questions (it’s YOUR body after all!), that he will answer your questions in a timely and respectful manner, that she will take your concerns seriously, and that he or she will openly discuss your options for prostheses.

 

If you find that your surgeon is unresponsive or even hostile to valid questions pertinent to your care, find another physician. There are lots of good ones out there. And if you’re going to have something as major and long-lasting as a knee or hip replacement, do your homework and make sure that whatever is going into your body is something that will not cause problems later. You’re the one who’s going to have to live with the consequences.