Part one of this blog covered pain related to, and the eligibility criteria for a simultaneous double knee replacement. Eligibility criteria was provided to ensure you are well informed while making the decision and the current evidence suggests that a simultaneous double knee replacement is no more painful than a single knee replacement. Part two of this blog will address two more important topics related to double knee replacements, functional outcomes and risks associated with simultaneous double knee replacements.

Am I Going to be able to move better after a double knee replacement?

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Having knee replacements on both legs at the same time will probably lead to better functional outcomes. I will provide you with research evidence to help you understand why.

One research study compared people who had a single knee replacement with those who had a double knee replacement to determine if their functional outcomes were different.[1] Both groups had 59 people, 29 women and 30 men and the average age was 67. They found that people who had the single knee replacement were able to move quicker and walk longer distances after surgery for the first 1-2 weeks after surgery. This difference may not seem significant but it can impact if the person is sent home after surgery, where their long term outcome is better, or if they are sent to a nursing facility, where their outcome is typically not as good.

Another research study compared 122 simultaneous double knee replacements to 46 single knee replacements to determine outcomes after surgery.[2] The simultaneous double knee replacement group had an average of 5 days shorter hospital stay, less knee stiffness, better self-reported function and a lower cost.

Lastly, a third research study reviewed 511 knee replacements from a hospital database.[3] All the surgeries were done by the same surgeon, using the same technique, with the only difference being whether it was one or two knees replaced. Simultaneous double knee replacements led to improved range of motion, which is the measure of the amount of movement around the knee, and higher self-reported function. Self-reported function simply means if the person who had the knee replacement was doing better in their movements and daily activities when they completed a standardized and validated questionnaire.

In summary, as a physical therapy student, I believe that the research supports the functional outcome benefits of a double knee replacement compared to a single knee replacement. The studies that support improved function after a double knee replacement involved more people and had stronger research designs, two crucial components to deciding which research studies carry more weight in making clinical decisions.

Is a Simultaneous Double Knee Replacement Riskier?

Is a double knee replacement riskier? It depends! With any surgery there is always a very small chance that the person who is receiving the surgery may die. Please keep in mind that this risk is very low but it is not zero. The evidence regarding whether you are more likely to die during a simultaneous double knee surgery or a single knee surgery is inconclusive. Some studies have shown no difference in how many people die following this surgery[4] while other studies have shown that replacing both knees at the same time is linked to a higher chance of death. However, when quantified, the risk goes from 1 in 1000 for a single knee replacement to 2 in 1000 for a double knee replacement.[5]

With regards to other risks, studies have shown that replacing both knees at the same time leads to increased risk of cardiac, meaning heart, and pulmonary, meaning lung, complications.[4] This includes a 1% higher risk of developing deep vein thrombosis[5] and increased risk of pulmonary embolism.[4] A double knee replacement also increases your chance of more serious falls as both knees will be weak and require rehabilitation.[5]

However, if you are relatively healthy, under the age of 70, not diabetic and have a BMI of below 40, the risks are small.[5] Body Mass Index or BMI is a ratio of your height and weight to provide a measure of body fat. Additionally, when you undergo two single knee replacements, you are exposing yourself to the risks associated with that operation twice. Moreover, replacing both your knees at the same time is associated with a 2.5 times lower chance of in-hospital infection.[6]


In Part 2 of this blog we have covered how a simultaneous double knee replacement can impact the way you move after surgery and the risks associated with the surgery. To recap, the research discussed in this blog supports that simultaneous double knee replacements lead to better ability to move after surgery. In terms of risk, there is little difference between simultaneous double knee replacements and single knee replacements. However, it is important you consider your own health status and consult with your health care provider before making the final decision.

To start your single or double knee replacement recovery at-home today download the Curovate physcial therapy app. Curovate provides daily video physical therapy , the ability to measure your knee range of motion with the app and daily progress and recovery tracking to keep you motivated! Click on the links below to get started!

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1. Powell RS, Pulido P, Tuason MS, Colwell CW Jr, Ezzet KA. Bilateral vs unilateral total knee arthroplasty: a patient-based comparison of pain levels and recovery of ambulatory skills. J Arthroplasty. 2006;21(5):642-649. doi:10.1016/j.arth.2005.08.009

2. Gill SD, Hill-Buxton LM, Gwini SM, et al. Simultaneous (two-surgeon) versus staged bilateral knee arthroplasty: an observational study of intraoperative and post-operative outcomes. ANZ J Surg. 2020;90(5):826-832. doi:10.1111/ans.15766

3. Bagsby D, Pierson JL. Functional outcomes of simultaneous bilateral versus unilateral total knee arthroplasty. Orthopedics. 2015;38(1):e43-e47. doi:10.3928/01477447-20150105-59

4. Meehan JP, Danielsen B, Tancredi DJ, Kim S, Jamali AA, White RH. A population-based comparison of the incidence of adverse outcomes after simultaneous-bilateral and staged-bilateral total knee arthroplasty. J Bone Joint Surg Am. 2011;93(23):2203-2213. doi:10.2106/JBJS.J.01350

5. Clark C. 'not a haircut': Two knees, same day ... more risk? Medical News. Published February 14, 2019. Accessed June 5, 2022.

6. Poultsides LA, Memtsoudis SG, Vasilakakos T, et al. Infection following simultaneous bilateral total knee arthroplasty. J Arthroplasty. 2013;28(8 Suppl):92-95. doi:10.1016/j.arth.2013.07.005