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Image by sabinevanerp from pixabay.com. Person running. Why does my knee feel big, heavy, unnatural and weird after my total knee replacement? Implants used for knee replacements are on average 0.6 lbs heavier than a natural knee.

A total knee replacement can lead to improvement in function and reduced pain for people with knee osteoarthritis. However, there are people who have a total knee replacement that have more difficulty feeling that their new knee is a normal part of their body. [2] Studies estimate that the number of people that have ongoing pain and discomfort is about 20-30%.[2][3] People who have a more difficult recovery say that they have a feeling of heaviness in the knee. [1][2][3] If this is you, you’re not alone!

Is it normal for my knee replacement to feel unnatural?

Many people with a knee replacement have a difficult time accepting their newly replaced knee as a normal part of their body. Accepting their new knee and having a good relationship with it is a very important aspect of recovery that is often overlooked.[3] Rather than just focussing on physical function, healthcare professionals are beginning to recognize the importance of understanding people’s feelings and perceptions toward their new knee.

There have been some research studies that try to understand the lived experiences of people with knee replacements. One of these studies used a measure called the Patient’s Joint Perception Questionnaire (PJP) which asks people who have had a joint replacement a simple question, “How do you perceive your operated knee?.” The person can respond with 5 possible answers:

  • Like a native or natural joint
  • Like an artificial joint with no restriction
  • Like an artificial joint with minimal restriction
  • Like an artificial joint with major restriction
  • Like a non-functional joint

Two studies that used the PJP on total knee replacement patients found that only 32-39% of patients perceived their new knee to be like a natural joint; however, over half of the participants reported that their new knee felt either like a natural joint or an artificial joint with no restriction.[1][4] Less than 15% of patients in both studies reported major restriction and none reported a non-functional joint.[1][4]

If you have had a knee replacement and your knee still feels unnatural, this is perfectly normal. It’s normal for you to feel this way as recovery from a total knee replacement takes time. This doesn’t mean that you can’t reach full function or come to accept your knee as a normal part of your body.

Why does my knee replacement feel heavy?

X-ray of a total knee replacement. Why does my knee feel big, heavy, unnatural, and weird after my total knee replacement? Implants used for knee replacements are on average 0.6 lbs heavier than a natural knee. 
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Image by Andersonvr from pixabay.com

One of the studies that looked at people's perceptions of their knee replacement also asked them about why they perceived their knee to be unnatural. Sensation of heaviness was one of the reasons, along with pain and difficulty with specific movements. There has been plenty of research on pain and physical function, but Gibon et al. (2014) is the only study to explore the difference in weight between the natural joint and the implant that replaces it. They measured the weight of the implant and the cement that fixates it and compared it to the bone and soft tissue they removed. They found that the new knee weighed on average about 0.6 lbs more! This difference was analyzed and found to be significant.[2] This means that even though 0.6 lb does not seem like a lot, it is enough for people to feel the difference in their new knee.

The weight difference likely explains why your knee might feel heavier after a total knee replacement, as it actually weighs more than it did before. No research has been done yet on if this difference in weight could explain why some people have a more difficult recovery, but it does highlight the importance of strength training in rehabilitation, as more strength may be required to perform certain activities. If you have had a knee replacement it’s normal for your knee to feel heavier, this is nothing to be concerned about. It’s only a small difference in weight which can start to feel normal with appropriate rehabilitation after surgery.

Conclusion

It’s normal for people with a knee replacement to feel like their new knee is weird or unnatural, this is nothing to be concerned about. And why does your knee feel heavier after a knee replacement? It feels heavier because it is! The new knee joint is on average 0.6 lbs heavier than the natural joint. This may be a reason that people feel that their new knee is heavier, and this may contribute to perceptions of an unnatural knee joint.

Dedicating time to working on mentally accepting your new knee as a part of your body may help with the successful incorporation of your knee as part of your body. Given the weight of the total knee replacement implant, more strength may be required for certain activities which further emphasizes the importance of strength training in your recovery. The Curovate app provides you with daily physiotherapy exercises, allows you to track your progress and helps you stay consistent throughout your rehab journey. Curovate is a great tool to guide you through your rehab, restore your strength and improve your function; allowing you to get back to normal!

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References

1. Eichler, D., Beaulieu, Y., Barry, J., Massé, V., & Vendittoli, P. A. (2020). Perception of a natural joint after total knee arthroplasty. The Journal of arthroplasty, 35(2), 358-363.

2. Gibon, E., Mouton, A., Passeron, D., Le Strat, V., Graff, W., & Marmor, S. (2014). Doctor, what does my knee arthroplasty weigh?. The Journal of arthroplasty, 29(11), 2091-2094.

3. Moore, A., Eccleston, C., & Gooberman‐Hill, R. (2020). “It’s not my knee”–understanding ongoing pain and discomfort after total knee replacement through (re) embodiment. Arthritis Care & Research.

4. Varacallo, M., Chakravarty, R., Denehy, K., & Star, A. (2018). Joint perception and patient perceived satisfaction after total hip and knee arthroplasty in the American population. Journal of orthopaedics, 15(2), 495-499.