Sensitivity to the Metal Parts in a Knee Replacement

Knee replacement surgery is a very successful surgery; the vast majority of people who undergo this treatment for severe knee arthritis are satisfied with the surgery. However, not everyone loves their new knee. In fact, about 10-15 percent of people who undergo knee replacement are not happy with their results

Trying to determine why a knee replacement is painful can be a challenging problem for patients and healthcare providers. Sometimes the problem is clear, such as an infection or a worn-out knee replacement implant. However, other times, everything checks out fine. Your healthcare provider tells you there is nothing wrong, but your knee still hurts. What could be causing the pain? Could a reaction to the metal in the artificial implant in your body be the source of the problem?

Physical therapist helping man with knee trouble
Susan Chiang/Getty Images

Metal Sensitivity

Any metal that comes into contact with the body, either through the skin or embedded within the body, causes some degree of metal corrosion. This corrosion leads to the formation of metal ions that can react with proteins in your body; these can be experienced in your body as allergens and can elicit an immune response.

The most common metal ions found in knee replacement implants that can cause hypersensitivity include nickel, cobalt, and chromium. These metals are known to cause skin sensitivity in the general public; about 15 percent of people have nickel sensitivity. The question has come up if a similar reaction due to metal hypersensitivity can occur within the body that leads to pain and stiffness after joint replacement

This has been a difficult question to answer. Most people, even those with known hypersensitivity skin reactions to metal, don't have a hypersensitivity to a joint replacement implant. Similarly, many people who are suspected of having a hypersensitivity response to a joint replacement do not have skin reactions to these metals.

Skin testing has not been shown to be useful to either prevent or diagnose a metal hypersensitivity to a metal joint replacement.

Hypersensitivity Reactions

There are two reactions that seem to occur in patients who have metal hypersensitivity to a knee replacement implant. The first is a skin reaction called dermatitis. In this condition, a skin rash that looks like eczema can occur. This is typically located over the front of the knee, although in some people can become more widespread. Dermatitis is most often managed with the help of a dermatologist, and fortunately is usually well controlled with topical steroid creams. 

The other reaction that can occur is called synovitis. The synovium is the lining of the knee joint, and a condition that causes inflammation of this tissue is called synovitis. Synovitis can occur with infections of the knee, traumatic injuries to the joint, or when there is a hypersensitivity response. The challenge is there are several conditions that can cause synovitis of the knee joint, but no test to confirm metal hypersensitivity as a cause. Therefore, this is considered a diagnosis of exclusion, meaning every other cause should be eliminated, and only then should metal hypersensitivity be suspected.

Treatment Options

The challenge with metal hypersensitivity is that typically the diagnosis is unclear (there is no test for the condition) and most often the symptoms are annoying, but not disabling. On top of that, the only possible way to correct the problem, if metal hypersensitivity is the actual cause, is to remove the implant and replace the knee with a special implant made of ceramic or titanium.

Therefore, any time metal hypersensitivity is suspected as the source of knee pain or stiffness after replacement, you should proceed with great caution. Even academic and up-to-date surgeons are just learning about this condition, and the optimal treatment is not clear. Performing additional surgery may or may not be helpful. That said, people struggling with pain after replacement may want to consider if this could be a source of pain.

There is no data to support the routine use of ceramic (zirconium) or titanium implants, even in people with concerns for possible hypersensitivity. The use of these implants is considered experimental and should be done with caution. That said, there are limited reports with short-term follow up that demonstrate some effective results.

A Word From Verywell

Allergy or sensitivity to metal implants used in orthopedic surgery is causing increasing concern among patients who are facing surgery. Some patients to have ongoing symptoms of pain after surgery are looking to the implants inserted see if they may be causing the problem. Scientific data is not clear as to whether metal implants are a source of pain for people to have ongoing symptoms after joint replacement surgery. However, people who do have the symptoms may benefit from the implantation of artificial joints that are made of non-metallic materials. If you were concerned about metal hypersensitivity, it is worthwhile having a conversation with your surgeon to discuss the possible options to prevent this problem.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Kahlenberg CA, Nwachukwu BU, McLawhorn AS, Cross MB, Cornell CN, Padgett DE. Patient Satisfaction After Total Knee Replacement: A Systematic ReviewHSS J. 2018;14(2):192–201. doi:10.1007/s11420-018-9614-8

  2. Lachiewicz PF, Watters TS, Jacobs JJ. Metal Hypersensitivity and Total Knee Arthroplasty. J Am Acad Orthop Surg. 2016;24(2):106–112. doi:10.5435/JAAOS-D-14-00290

  3. Faschingbauer M, Renner L, Boettner F. Allergy in Total Knee Replacement. Does It Exist?: Review ArticleHSS J. 2017;13(1):12–19. doi:10.1007/s11420-016-9514-8

Additional Reading

By Jonathan Cluett, MD
Jonathan Cluett, MD, is board-certified in orthopedic surgery. He served as assistant team physician to Chivas USA (Major League Soccer) and the United States men's and women's national soccer teams.