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How much does a knee replacement weigh?
The question was on my mind before and after my surgery so I decided to do some research to find out the answer. I found that there’s no single definitive answer.
The average weight of men’s knee replacements are 1.12 lbs and women’s knee replacements average .76 lbs (both weights include the cement).
Although the weight of an individual knee replacement varies depending on the size of the knee and the size of the patient, implants only weigh a few pounds. Thus, there is no single answer to the question.
In this article I will share the information that I have learned while researching this question.
Approximate Weight of a Total Knee Joint Replacement
The weight of the prosthesis will be more than the weight of the bone removed.
The weight will vary depending on your knee and body size.
Bone, soft tissue and bone reamings will be removed first. Next there is the cumulative weight of the prosthesis, bone cement, patellar component and the polyethylene liner that will be inserted in to your knee (read about my hospital stay after knee replacement).
I read one study of 20 consecutive patients who had TKR surgery. They measured and weighed the collected materials taken from the knee and also weighed the components inserted in to the knee.
Mean weight of the new knee (plus cement used) was 509 grams (1.12 pounds) for men and 345.5 grams (.76 pounds) for women.
The average weight of the bone and soft tissue removed was 167.5 grams (.36 pounds) for men and 130 grams (.28 pounds) for women.
Generally, you will not notice the small weight difference.
Components and Material of a knee replacement
Titanium is the metal of choice now for knee implants. My only experience with titanium prior to my TKR was using titanium metal bats when playing softball.
The titanium bats definitely improved the speed of which the ball came off the bat and I no longer enjoyed fielding balls at shortstop.
Titanium is an elemental metal, meaning that it is not man-made. It is an extremely low-density metal and it does not corrode.
It is especially useful for medical applications. Titanium has the lowest strength-to-weight ratio of any metal. Pure titanium is as strong as steel but weighs approximately 45% less.
To construct a prosthetic knee the titanium is melted down and then cast in to components which will eventually form the replacement knee joint.
Stainless Steel Versus Titanium For Your Knee Replacement
- Titanium is stronger and lighter (45% less) than Stainless Steel.
- Titanium has superior strength under repeated load stresses than Stainless Steel.
- Titanium is less rigid than Stainless Steel and limits the stress on the bone structure it is attached to.
- Titanium is less prone to generating immune reactions because it is corrosion resistant.
Does A Titanium Knee Feel Heavier Than A Normal Knee (Will I Weigh More After TKR)?
You may think that when you weigh yourself post TKR that you can knock off a few pounds due to the weight of your new metal knee. Unfortunately this is not true.
The implant will not make any significant difference in your weight.
I read one study that revealed that pre-operative weight and post operative weight one year after surgery showed little or no effect on the patients weight after surgery.
Of course if you don’t take your rehabilitation seriously, or if the procedure goes wrong, then you may gain weight.
I have mentioned in previous articles about the benefit of a 6 week (or more) pre-surgical exercise program that can improve pre-operative function and muscle strength.
I hope this article has helped answer the question of “how much does a knee replacement weigh”. I am sorry that I could not give a definitive answer because we are all different and the new knee is designed specifically for the individual.
You won’t feel a “heavy” knee and the new knee will not make you weigh more than you did before surgery. What comes out of your knee joint and what goes back in to the joint makes for an insignificant increase in body weight.
Titanium is especially good for knee replacements and should provide you with many years of good knee function.