In 2021, Ko et al. found that male sex, low family earnings, surgical technique type (bilateral), length of stay (LOS) ≥ 35 days, and transfusions were risk factors for postoperative adverse events after TKA in individuals with idiopathic knee osteoarthritis. The aforementioned authors analyzed 560,954 individuals older than 50 years. The risk of PJI was evaluated with 8 independent parameters: sex, age, place of residence, family earnings, hospital bed size, type of surgical technique (unilateral or bilateral, primary or revision TKA), LOS, and the use of transfusions [21].

In 2022, the MAC carried a population-based cohort investigation utilizing linked administrative databases. The multivariable analysis showed that male gender, younger age, type II diabetes, posttraumatic osteoarthritis, patellar resurfacing, and discharge to convalescent care were related to an increased risk of PJI [11].

In an article with level 2 evidence (prognostic study), the independent risk factors for PJI (in diminishing order of importance) were congestive heart failure, chronic pulmonary illness, preoperative anemia, diabetes, depression, renal illness, pulmonary circulation disorders, obesity, rheumatologic illness, psychoses, metastatic tumor, peripheral vascular illness, and valvular illness [22].

In 2013, Chen et al. showed that the principal factors associated with PJI following TKA were body mass index (BMI), diabetes mellitus, hypertension, steroid treatment, and rheumatoid arthritis. The study had insufficient evidence to demonstrate that the male sex was associated with PJI after TKA. A statistical analysis showed no correlations between urinary tract infection, fixation technique, American Society of Anesthesiology (ASA) score, bilateral procedure, age, transfusion, antibiotics, bone graft, and PJI [23].

A study with level 2 evidence (prognostic study) reported by Kurtz et al. in 2010 showed that women had a lower risk of PJI than men. Comorbidities also increased TKA infection risk. Individuals receiving public assistance for Medicare premiums were at increased risk for PJI. Hospital factors did not contribute to an increased risk of infection. PJI occurred at a fairly elevated percentage in Medicare individuals, with the greatest risk of PJI within the first 2 years following TKA; nonetheless, around 25% of all PJIs occurred after 2 years [20].

Cordtz et al. observed that individuals with rheumatoid arthritis had a diminished 10-year risk of revision TKA, whereas the risk of PJI was increased compared with individuals with osteoarthritis after TKA. Previous treatment with biological disease-modifying antirheumatic drugs was not related to an increased risk of PJI [24].

In an investigation with level 3 evidence (therapeutic study), Pancio et al. found that a higher proportion of individuals who had undergone multi-ligament knee surgery experienced infections compared with matched controls (7% vs. 1%), respectively. Previous multi-ligament surgery was associated with a greater risk of PJI [25].

Previous septic arthritis has also been recognized as a PJI risk factor [25]. Pooled data from more than 1300 arthroplasties in published papers revealed a PJI rate of 5.96% when a previous infection occurred in the same articulation. The risk of infection was lower because the TKA surgery was delayed from the resolution of the previous infection.

In 2015, Singh et al. found that smoking was related to an elevated risk of PJI after primary TKA. Tobacco use status was accessible for 7926 (95%) individuals and was not accessible for 446 (5%); 565 (7%) currently smoked tobacco. The hazard ratios for PJI were higher in current tobacco users than in nonusers [26]. Cessation of smoking before TKA is strongly recommended.

According to Man et al., malnutrition is a relevant but changeable risk factor for postoperative adverse events and unfavorable results in orthopedic surgery [27]. They sought to detect biomarkers of malnutrition in individuals undergoing TKA that could be predictive of adverse postoperative complications in the hospital, to identify patients at risk and optimize their nutritional status prior to TKA. These authors analyzed 624 patients in whom possible biomarkers of pre-operative malnutrition, including hypoalbuminemia (serum albumin < 3.5 g/dL), total lymphocyte count (TLC) (<1500 cells/mm³), and BMI, were evaluated for associations with in-hospital postoperative adverse events. The frequencies of hypoalbuminemia, low TLC, overweight, obesity class I, and obesity class II were 2.72%, 33.4%, 14.8%, 44.5%, and 26.9%, respectively. There were significant relationships between hypoalbuminemia and type II obesity (BMI ≥ 30.0 kg/m²) and PJI percentages and no significant relationships between these adverse events and low TLC, overweight, or type I obesity. It was also found that individuals with hypoalbuminemia or type II obesity with gouty arthritis were more prone to experience PJI. The authors concluded that hypoalbuminemia and type II obesity together were dependable biomarkers of preoperative malnutrition that could predict PJI following TKA; however, low TLC, overweight, and type I obesity were not significantly related to an increased risk of PJI [27].

In a level 3 evidence study (therapeutic study) published in 2017, Bedard et al. observed that intra-articular knee injections with corticosteroids, hyaluronic acid, or other drugs prior to TKA were related to an increased risk of PJI, and this association appeared to be time dependent: the shorter the delay between injection and TKA, the greater the likelihood of PJI [28]. The proportion of patients undergoing TKAs who developed PJI was greater in those who were given an injection prior to TKA than in those who were not (4.4% vs. 3.6%). Similarly, the proportion of patients undergoing TKAs who developed PJI requiring surgical reintervention was also greater among those who received an injection prior to TKA than in those who did not (1.49% vs. 1.04%). An analysis of the months between injection and TKA showed that the odds of PJI were greater for patients injected up to 6 months between injection and TKA, as were the odds of surgical intervention for TKA infection when the injection was within 7 months of TKA. When the time span between injection and TKA was longer than 6–7 months, the ORs were no longer raised [28].

In 2018, Shohat et al. investigated the relationship between glucose variability and postoperative adverse events after TKA (level 4 of evidence study) [29]. They analyzed data on 2698 individuals who had experienced TKA at a single center. Individuals with a minimum of two postoperative glucose values per day or more than three values overall were included in the research. Glucose variability was evaluated utilizing a coefficient of variation. The MSIS criteria were utilized to establish PJI. Some 19.9% of the patients had diabetes. Greater glycemic variability was related to increased LOS, 90-day mortality, PJI, and SSI. Adjusted analyses showed that for every 10-percentage-point rise in the coefficient of variation, the LOS increased by 6.1%, and the risks of PJI and SSI increased by 20% and 14%, respectively. These associations were independent of the year of the surgical procedure, age, BMI, Elixhauser comorbidity index, diagnosis of diabetes, in-hospital utilization of insulin or steroids, or mean glucose values throughout hospitalization. They concluded that greater glucose variability in the postoperative period was related to increased percentages of SSI and PJI after TKA. According to Shohat et al., it is paramount to control glucose variability in the early postoperative phase [29].

It has been published that the likelihood of PJI following primary TKA can be reduced by decreasing the patient’s weight, which will also minimize the risk of implant failure [17].