Are you deciding between a staged single knee replacement or a simultaneous double knee replacement? Well, you have clicked on the right link! This two part blog will give you an easily digestible but informative overview on 4 key factors to consider in your decision between a traditional single knee replacement or double knee replacement. If you’re reading this blog it is likely that you already know what a total knee arthroplasty is and what this procedure entails. But if you would like to know more about the single knee procedure click here for more information. Part 1 of this blog will focus on the factors of pain and eligibility criteria and how they may influence your decision on opting for a double knee replacement or going with the traditional one knee at a time route.

Image by @yuhao, from Unsplash

Having 2 knees done at the same time will cause double the pain, right?

Pain is a huge factor that plays a part in every individuals' decision. Regardless of whether someone opts for a single knee or double knee replacement, pain will influence the path to recovery. You may think that having 2 knees done at the same time would just equate to double the pain. Yet, a study conducted on 50 double knee replacements and 30 single knee replacements demonstrated that there was no significant difference in pain intensity or recovery .[1] This study of 80 individuals with an average age of 63, showed that 30 days after their operations both groups had felt much less pain and were able to resume a lot of their everyday activities.[1] Thus the authors of this study support the use of simultaneous double knee replacement due to similar outcomes and reduced cost.[1]

On the opposing side, a study conducted in Denmark showed that double knee replacements have higher rates of postoperative complications and need for reoperation. [2] This study included 344 double knee replacements, and “higher” in this case means a total of 46 people who stayed in hospital for longer than the usual 4 days because of a known complication, and a total of 9 people who required a reoperation.[2] This is important to note because these complications are a source of additional pain.

A factor that has been shown to influence pain from a simultaneous double knee replacement is the form of anesthesia that is used. A study performed on 71 simultaneous double knee replacements showed that periarticular injections (numbing medication that is applied around the knee joint itself) had better pain relieving outcomes compared to an epidural block (a numbing medication that is applied at the spinal cord to numb the entire lower body).[3] Thus if you are leaning towards a double knee replacement, before undergoing the procedure it is best to consult your surgeon on the options you have for pain relief.

So do I fit the bill for a double knee replacement?

Unfortunately, there is no clear cut answer to this question. Eligibility for this procedure is determined by the surgeon, the hospital, and health plan. Dr. Ettore Vulcan and Dr. Stavros G. Memtsoudis provide 3 considerations that are meant to disclude an individual from having this procedure done due to increased risks associated with these factors.

1.The age of the patient; extreme age should be avoided [4]

2. The American society of anesthesiologist suggest the exclusion of patients with significant end organ dysfunction [4]

3. People with existing complications or disease: patients at risk for heart and lung complications should undergo a pre-screening. Similarly heart and lung diseases such as congestive heart failure or chronic obstructive lung disease should be excluded [4]

This criteria is just one of many different considerations that surgeons and hospitals will use to determine the risk associated with a simultaneous double knee replacement. But this criteria for exclusion is neither extensive or absolute. For instance the first point concerning “extreme age” is vague and lacking substantial evidence as it is difficult for anyone to say with certainty at what age someone should be excluded.[5] In fact, while some surgeons will not perform this procedure on anyone over the age of 75, others have performed the same procedure on people over the age of 90. [5] This is to say that age should not be the sole or deciding factor as to whether or not you are able undergo this procedure, especially if you’re in good health.

Likewise, many surgeons and institutions have regulations related to weight and obesity. Surgeons will use the body mass index a rough measure of a person's body fat based on their weight and height. The current school of thought is that having more body, or a higher BMI, is a reason to exclude someone from having a double knee replacement. [6] Yet, a recent study with 1070 individuals ranging from a normal BMI (18.0-25.0 kg/m2), an overweight BMI (25.0–29.9 kg/m2), and an obese BMI (>30 kg/m2) showed that being overweight or obese may not have the adverse impact that they are believed to have. [6] In fact, the authors of this study could not find a link between obesity and the rate of complications such as infections or stroke. Hence, providing evidence for surgeons to perform simultaneous double knee replacement on obese and overweight patients.[6]

So why should you care about this criteria? First and foremost knowing these factors will improve your ability to make an informed decision. The exclusion criteria may tell you about what personal factors may increase your risk for complications, it is up to you to carefully weigh these risk versus the benefits. Secondly, knowing that the criteria for eligibility is not absolute will help you advocate for the decision you make. Finally, recognize that the criteria can and should be used in collaboration with your surgeon to determine which procedure is right for you.


In Part 1 of this blog we have covered the aspect of pain and the eligibility criteria for a simultaneous double knee replacement. To recap, pain will undoubtedly be a part of the journey to recovery, but current evidence shows that a double knee replacement is not more painful than a single knee replacement. Furthermore, the current eligibility criteria is not set in stone and may vary from surgeon to surgeon. Knowing the criteria improves your understanding of the risk and ability to make the right decision for your circumstances. It is important to note that these 2 factors are just some of many factors that should be considered. Part 2 of this blog will discuss in greater detail the factors of adverse events and functional outcomes and how they may influence your choice.

Eager to learn more? Click here to learn more about knee replacements and many more relevant topics on the Curovate blog. Or download the Curovate app, an evidence based app that will provide you with a physical therapy plan, guided video exercises, and more to assist you along your journey to recovery! Download Curovate today by clicking the links below!

app-store-badge-128x128-2 google-play-badge-128x128


1. Alghadir AH, Iqbal ZA, Anwer S, Anwar D. Comparison of simultaneous bilateral versus unilateral total knee replacement on pain levels and functional recovery. BMC Musculoskelet Disord. 2020;21(1):246. Published 2020 Apr 15. doi:10.1186/s12891-020-03269-3

2. Lindberg-Larsen M, Pitter FT, Husted H, Kehlet H, Jørgensen CC; Lundbeck Foundation Centre for Fast-Track Hip and Knee Replacement Collaborative Group. Simultaneous vs staged bilateral total knee arthroplasty: a propensity-matched case-control study from nine fast-track centres. Arch Orthop Trauma Surg. 2019;139(5):709-716. doi:10.1007/s00402-019-03157-z

3. Tsukada S, Wakui M, Hoshino A. Pain control after simultaneous bilateral total knee arthroplasty: a randomized controlled trial comparing periarticular injection and epidural analgesia. J Bone Joint Surg Am. 2015;97(5):367-373. doi:10.2106/JBJS.N.00373

4. Vulcano E, Memtsoudis S, Della Valle AG. Bilateral total knee arthroplasty guidelines: are we there yet?. J Knee Surg. 2013;26(4):273-279. doi:10.1055/s-0032-1329721

5. Clark C. 'not a haircut': Two knees, same day ... more risk? Medical News. Published February 14, 2019. Accessed June 2, 2022.

6. Cao G, Chen G, Yang X, et al. Obesity does not increase blood loss or incidence of immediate postoperative complications during simultaneous total knee arthroplasty: A multicenter study. Knee. 2020;27(3):963-969. doi:10.1016/j.knee.2020.01.012