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Bilateral vs Single Side Total Knee Replacement

Almost 800,000 total knee replacements are performed every year in the U.S., and this number will continue to grow as our population ages. The most common reason for having a total knee replacement (TKR) is severe joint damage, usually caused by osteoarthritis, rheumatoid arthritis, other inflammatory joint conditions, infections, or previous injuries.[1]

Most patients return to their usual activities within six weeks after surgery and fully recover in six months.[2] In some cases, it is necessary to replace both knees and the surgeon will determine whether to replace them one at a time in staged surgeries (unilateral total knee replacement), or to replace both knees during the same surgery (bilateral total knee replacement). Both options have risks and benefits.

Patient Selection for Bilateral Total Knee Replacement

A bilateral total knee replacement is a lengthier surgery and requires patients to be under anesthesia for a longer period of time. To limit risks, surgeons must carefully select patients for this procedure.

Bilateral TKR Selection Criteria[3]

  • Anatomical indications:

    • Chronic pain affecting daily activities
    • X-rays indicating joint damage
    • Physical exam indicating stiffness, deformity, and joint instability
  • American Society of Anesthesiologists (ASA) Classification:

    helps predict peri-operative risks. It is recommended that patients who undergo bilateral TKR be classified as ASA 1 or 2 (a higher classification indicates a higher level of risk)[4]:
    • ASA 1: a healthy adult patient who drinks minimal or no alcohol and who does not smoke
    • ASA 2: a patient with mild systemic disease that does not affect function; a patient who smokes, drinks alcohol socially, is obese (BMI less than 40), has well-controlled diabetes or hypertension, and/or has mild lung disease
  • Additional considerations:

    • Age: best outcomes occur in patients between 50 to 90 years of age; younger patients are more likely to require revision surgery later in life, while older patients are at a higher risk of complications due to other health conditions
    • Mental Health: the pain, physical therapy, and activity limiations of the recovery precess can negatively impact mental health; mental health conditions such as depression or anxiety may need to be addressed prior to surgery to facilitate the

Each surgeon must weigh the risks and benefits of surgery on a case-by-case basis. Patients selected for bilateral TKR must be healthy and able to tolerate a more challenging postoperative period. Consequently, in the U.S., the number of bilateral TKRs is approximately 3-6% of a surgeon’s total number of knee replacement surgeries per year.[5,6]

Timeline for Recovery After Bilateral Total Knee Replacement

  • Hospital stay: 1-3 days
  • Inpatient physical rehabilitation (required by approximately 2/3 of patients): 2-3 weeks
  • Outpatient physical therapy: 6-8 weeks
  • Home exercises: Up to 12 months[7]

Physical Therapy After Bilateral Total Knee Replacement

Typical physical therapy after knee replacement surgery lasts up to eight weeks, but it can longer depending upon the individual recovery process. Physical therapy will start the same day as surgery or the following day. While the patient remains in the hospital, therapy is performed twice daily.

Outpatient sessions are two to three times per week, and last about one hour. The physical therapist will work on the range of motion in the knee joint, and strengthen the leg muscles to support the joint. After bilateral TKR, both knees are addressed during each session, Typically, these sessions are more intense, especially in the first few weeks after surgery.[8]

Risks of Bilateral Total Knee Replacement

  • Longer surgical time

    surgery to replace both knees takes around 3 hours, as opposed to 1 to 2 hours for a single knee more time under anesthesia can increase unwanted outcomes.
  • Longer initial hospital stay

    Longer initial hospital stay: patients who have both knees replaced at the same time may need more help initially. and may benefit from a longer hospitalization
  • Increased blood loss

    Increased blood loss: during bilateral TKR, the amount of blood lost doubles as compared to replacing a single knee (though blood loss has not been found to affect the need for blood transfusion).[9,10]
  • Pulmonary embolism and deep vein thrombosis (DVT)

    Pulmonary embolism and deep vein thrombosis (DVT): several studies have shown that pulmonary embolism and DVT appeared to be more common in bilateral TKR[8]; blood clot prevention is managed with anticoagulant medications
  • Increased pain and decreased function

    Increased pain and decreased function: patients suffer significantly more pain following bilateral TKR and do not have the ability to rely on a healthy leg during recovery, which can be challenging for mobility and other acitivities
  • Infection and need for revision surgery

    Infection and need for revision surgery: as there are two surgical sites for bilateral TKR, the risk for infection increases; however, most studies have not found a significant difference in infection rates between bilateral and unilateral knee replacement[9]

Benefits of Bilateral Total Knee Replacement

  • Less time under anesthesia
  • Undergoing a single surgery instead of two procedures
  • Less cost (undergoing one surgery, hospital stay, and round of physical therapy is less expensive as compared to undergoing two separate procedures)
  • Shorter overall recovery as compared to staged unilateral knee surgery
  • Less time off from work for recovery[11]

When unilateral or bilateral TKR, many people want to know exactly how much time and money can be saved by replacing both knees at the same time.

Wan et al studied cost, safety, and rehabilitation time compared between single staged knee replacement and bilateral knee replacement. They found that in patients who underwent bilateral TKR, there was a decrease in the length of hospital stays by 5.71 days per patient, with an estimated savings of $3,448 per patient. They also found that bilateral TKR reduced the operation time by 27.4 minutes and decreased physical therapy sessions by 18.6%.[11]


Bilateral total knee replacement has been shown to provide many benefits to patients who meet the selection criteria. The safety and post-surgical complication rates have also been shown to be comparable to unilateral knee replacement rates. When considering knee replacement, patients should thoroughly discuss treatment options with their orthopedic surgeon.

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Sheth, N. P., & Foran, J. R. H. (2024, February). Total knee replacement. OrthoInfo. https://orthoinfo.aaos.org/en/treatment/total-knee-replacement/
Adie, S., Harris, I., Chuan, A., Lewis, P., & Naylor, J. M. (2019). Selecting and optimising patients for total knee arthroplasty. Medical Journal of Australia, 210(3), 135–141. https://doi.org/10.5694/mja2.12109
Pfeil, J., Höhle, P., & Rehbein, P. (2011). Bilateral endoprosthetic total hip or knee arthroplasty. Deutsches Ärzteblatt International. https://doi.org/10.3238/arztebl.2011.0463
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American Association of Hip and Knee Surgeons. (n.d.). Total joint replacement: A breakdown of costs. AAHKS Hip and Knee Care. https://hipknee.aahks.org/total-joint-replacement-a-breakdown-of-costs/
InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. Osteoarthritis of the knee: What can you expect before and after surgery? 2019 Jul 18. Available from: https://www.ncbi.nlm.nih.gov/books/NBK544981
Liu, L., Liu, H., Zhang, H., Song, J., & Zhang, L. (2019). Bilateral total Knee Arthroplasty. Medicine, 98(22). https://doi.org/10.1097/md.0000000000015931
Alameri, M. A., Sulaiman, S. A., Ashour, A. M., & Al-Saati, M. F. (2020). Bilateral versus unilateral total knee replacement with 35-day morbidity and mortality: A bi-centre prospective cohort study. International Journal of Surgery Open, 26, 36–41. https://doi.org/10.1016/j.ijso.2020.08.005
Wan, R. C., Fan, J. C., Hung, Y.-W., Kwok, K.-B., Lo, C. K., & Chung, K.-Y. (2021). Cost, safety, and rehabilitation of same-stage, bilateral total knee replacements compared to two-stage total knee replacements. Knee Surgery & Related Research, 33(1). https://doi.org/10.1186/s43019-021-00098-z
Last edited on April 30th, 2024 11:20 pm