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Risk of Blood Clots Does Not Appear Higher in Total Knee Replacement Patients Who Recovered from COVID-19

In a study conducted at Hospital for Special Surgery (HSS), researchers found that there was no significant difference in endothelial function before or after total knee replacement (TKR) surgery in patients who had recovered from COVID-19 versus those who did not have the virus. Additionally, there was no association with the severity of COVID-19, or the time since infection. These findings were presented at the 2022 Spring American Society of Regional Anesthesia and Pain Medicine (ASRA) Annual Meeting.1

Endothelial injury, or damage to the lining of the blood vessels, can be a major cause of blood clots after surgery. It has also been found in patients infected with COVID-19. 

Investigators aimed to gain insights into whether the risk of endothelial dysfunction continues after an infection with COVID-19 resolves, and if there is a need for more aggressive Deep Vein Thrombosis (DVT) prophylaxis in TKR patients with a history of COVID-19 infection. Aggressive DVT prophylaxis consists of pharmacologic and nonpharmacologic measures to diminish the risk of deep vein thrombosis and pulmonary embolism.

“Previous studies have demonstrated endothelial dysfunction in patients with active COVID-19 infection as manifested by higher rates of thromboembolic events. Consequently, therapeutic anticoagulation is recommended for hospitalized patients with acute and significant disease from the virus,” said HSS anesthesiologist Kethy Jules-Elysee, MD. “It remains unknown to what extent this predisposition to endothelial dysfunction persists upon resolution of active COVID-19 infection, implying a possible need for higher level of thromboprophylaxis in these patients postoperatively.”

She continued “Postoperative thrombosis is always a concern in patients undergoing total knee arthroplasty (TKA). This has been attributed to endothelial dysfunction from Virchow's triad. Given the projected increase in demand of TKA surgeries and the continued rise of COVID-19 cases, it is significantly important to assess the risks of postoperative thrombosis in the setting of both TKA and previous COVID-19 infection.”

Fifty-three patients with SARS-CoV-2 antibodies were identified for the case group and 48 patients without SARS-CoV-2 for the control group; all had received a primary TKR for knee osteoarthritis. Endothelial function was analyzed non-invasively via a reactive hyperemia procedure with a VENDYS-II device, once before surgery and once on postoperative day 1. Endothelial function was quantified using the vascular reactivity index (VRI) ranging between 0 (poor) to 3.5 (excellent). 

There was no significant difference between the average pre- and postoperative VRI in both patient groups, nor was there a significant difference in VRI scores before surgery vs after surgery. 

“Findings suggest no increased risk of DVT after TKA in SARS-CoV-2 IgG positive patients,” Dr. Jules-Elysee noted.

Postoperative VRI was not correlated with the duration or severity of COVID-19 infection. Decreased postoperative VRI was also not associated with increased length of hospital stay.

These results indicate that more aggressive DVT prophylaxis is likely not needed in TKR patients who have fully recovered from COVID-19.

When considering follow-up studies, Dr. Jules-Elysee noted “Since patients with a history of severe or prolonged infection with COVID-19 were not included in the study, further research on these patients is needed.”


1. Kethy Jules-Elysee, Carola Hanreich, Friedrich Boettner, Anna Jungwirth-Weinberger, Alison Zhao, Robyn Schultz, Ilya Bendich, Lisa Mandl. “Risk of thromboembolic events as measured by endothelial function is not elevated in total knee replacement patients with history of COVID disease.” Presented at: 47th Annual Regional Anesthesiology and Acute Pain Medicine Meeting of the American Society of Regional Anesthesia and Pain Medicine (ASRA), March 31-April 2, 2021; Las Vegas, NV.

About HSS

HSS is the world’s leading academic medical center focused on musculoskeletal health. At its core is Hospital for Special Surgery, nationally ranked No. 1 in orthopedics (for the 14th consecutive year), No. 2 in rheumatology by U.S. News & World Report (2023-2024), and the best pediatric orthopedic hospital in NY, NJ and CT by U.S. News & World Report “Best Children’s Hospitals” list (2023-2024). In a survey of medical professionals in more than 20 countries by Newsweek, HSS is ranked world #1 in orthopedics for a fourth consecutive year (2023). Founded in 1863, the Hospital has the lowest readmission rates in the nation for orthopedics, and among the lowest infection and complication rates. HSS was the first in New York State to receive Magnet Recognition for Excellence in Nursing Service from the American Nurses Credentialing Center five consecutive times. An affiliate of Weill Cornell Medical College, HSS has a main campus in New York City and facilities in New Jersey, Connecticut and in the Long Island and Westchester County regions of New York State, as well as in Florida. In addition to patient care, HSS leads the field in research, innovation and education. The HSS Research Institute comprises 20 laboratories and 300 staff members focused on leading the advancement of musculoskeletal health through prevention of degeneration, tissue repair and tissue regeneration. In addition, more than 200 HSS clinical investigators are working to improve patient outcomes through better ways to prevent, diagnose, and treat orthopedic, rheumatic and musculoskeletal diseases. The HSS Innovation Institute works to realize the potential of new drugs, therapeutics and devices. The HSS Education Institute is a trusted leader in advancing musculoskeletal knowledge and research for physicians, nurses, allied health professionals, academic trainees, and consumers in more than 165 countries. The institution is collaborating with medical centers and other organizations to advance the quality and value of musculoskeletal care and to make world-class HSS care more widely accessible nationally and internationally.