The Increase in Total Knee Replacement Surgery in China: A 10-Year Real-World Study

Total knee arthroplasty (TKR) is the most common and costly surgical procedure performed, and it is considered one of the most successful clinical interventions for patients suffering from severe knee osteoarthritis (OA). The incidence of TKR, including demographics, incidence rates, lengths of hospital stay, and costs, was estimated from 2010 to 2019 by analyzing data extracted from the Joint Surgery Department in our hospital, which included a total of 6770 patients. We calculated the TKR risk ratios to compare the rate of TKR between different covariables such as gender, age group, and primary diagnoses. The annual volume of TKR increased by fivefold (5.14%), with a higher incidence observed in the 60 to 69 age group constituting approximately 36% of cases. There has also been an increase in incidence among young people (<50), which now stands at 6.2%. The rate ratio (RR) per female vs. male was found to be 3.0 and the RR of OA vs. RA was 0.09. The mean average length of stay (ALOS) in the hospital decreased from 15 to just 5 days during this period. Additionally, the adjusted mean cost per patient increased significantly from ¥ 38261 ± 3630.63 to ¥ 53115.17 ± 2831.35. The majority of TKR recipients were over 60 years old with osteoarthritis being identified as the main causative agent. It is worth noting that women are more susceptible to knee arthritis and there is a concerning shift toward younger individuals being affected by this disease. Our results indicate a rise in in-hospital costs alongside a significant decline in hospital ALOS for TKR procedures. We predict an unprecedented rise in TKR incidence in the coming years due to population aging and improving economic conditions in China.

Is the Prophylactic Administration of Povidone Iodine Intranasally Preoperatively in Elective Total Knee Replacement as Effective as MRSA Prophylactic Screening and Mupirocin Treatment?—A Retrospective Analysis

Surgical Site Infections (SSIs) remain a prevalent issue in healthcare. An average of 2% to 4% of all Total Knee Arthroplasties (TKA/TKR) result in a Prosthetic Joint Infection (PJI) (Ashraf et al. , 2018). These surgical site infections cause significant distress to the patient and require extended courses of antibiotic treatment and revision surgery of the infected joint. SSIs also reduce financial reimbursement to the surgery facility and affect the performing surgeon’s performance scores. To prevent surgical infection, healthcare facilities have implemented various screening or decolonization methods to prevent surgical infection to may cause infection. Various treatment methods exist for managing MRSA preoperatively which include Povidone Iodine (PI) application as a universal decolonization method and/or screening every patient pre-operatively for MRSA and treating MRSA-positive patients with Mupirocin ointment. Both interventions are well-established in the literature. At the author’s facility, the elective TKR populations were analyzed while each intervention was implemented. In 2019 TKR patients underwent MRSA swabbing and testing and in 2021 PI decolonization was the decolonization method of choice. The study revealed that MRSA testing and swabbing were better at reducing SSI related to MRSA than Povidone Iodine decolonization.

Robotics in total knee replacement:Current use and future implications

Robotic total knee replacement(TKR)surgery has evolved over the years with the aim of improving the overall 80% satisfaction rate associated with TKR surgery.Proponents claim higher precision in executing the pre-operative plan which results in improved alignment and possibly better clinical outcomes.Opponents suggest longer operative times with potentially higher complications and no superiority in clinical outcomes alongside increased costs.This editorial will summarize where we currently stand and the future implications of using robotics in knee replacement surgery.

The Association between Surgery Laterality in Orthopedists and the Choices of Prostheses in Total Knee and Hip Replacement

Background: Most orthopedists are right-handed. However, osteoarthritis occurs with equal frequency over both sides. Does perfect and effective arthroplasty surgery require ambidextrous motor skills? Objectives: In this study, we aimed to investigate the clinical features of arthroplasty for hip and knee joints (THR and TKR) on different sides affected by orthopedist laterality. Patients and Methods: All right-handed orthopedists performed 64 right and 52 left primary THR among 100 patients, and 115 right and 118 left primary TKR among 192 patients. Clinical and surgical features were retrospectively reviewed and analyzed. The body mass index (BMI), inner diameter of acetabular cup liners (ACD), diameter of the femoral head (FHD), diameter of the femoral stem (FSD), and the femoral neck length (FNL) were included in THR-receiving patients. The BMI, femoral component (FC) size, tibial plate (TP) size, and thickness of articular surface inserts (ASI) were included in TKR-receiving patients. Results: No significant differences were observed in ACD, FHD and FSD between patients receiving right and left THR groups (p = 0.16, 0.11, and 0.05, respectively). Similarly, there were no significant differences in FC, TP, and ASI between patients receiving right and left TKR groups (p = 0.06, 0.80, and 0.46, respectively). However, FNL in left THR group was significantly longer than that in right THR group (p = 0.01). Conclusion: This study showed that dexterity or proprioception in handedness had no affect on bone resection and thicknesses of the polyethylene in TKR and acetabular reaming and femoral canal rasping in THR. However, it did lead to differences in femoral neck resection. Right-handed orthopedists significantly tend to perform excessive femoral neck cutting or prefer the larger size of FNL when performing left side THR, while no differences occur when performing TKR.

Population-Based and Personalized Design of Total Knee Replacement Prosthesis for Additive Manufacturing Based on Chinese Anthropometric Data

At present,most total knee replacement(TKR)prostheses on the market are designed according to the sizes of Caucasians.However,extensive studies have indicated that human anatomies differ among different ethnicities.A number of reports have indicated that Chinese TKR patients do not match with available prostheses.In this study,computed tomography(CT)images of 52 knees of Chinese men and women were used for anthropometric measurements.Index and geometric measurements were definedand used for correlation analysis.Key parameters from the measurement results were identified.Detailed geometries of knees were measured as coordinates.A deformable three-dimensional(3D)knee modelbased on anatomical coordinates correlating with the identified key parameters was generated.A pros-thesis was then designed according to the analyzed results.Surface matching analysis,bone resectionanalysis,and cadaveric trials were conducted and compared with commercial products to validate theproposed design.The femoral component designed by this study resulted in the highest accuracy(rootmean square point-to-surface(RMS PS),(1.08±0.20)mm)and lowest amount of resected bone volume(27412mm^(3))in comparison with two commercial knee prostheses.This study suggests a new approachfor population-based patient-specific femoral prosthesis design With a single,easilty acquired dimen-sion-namely,epicondyle width(ECW)-as input,a patient-specific femoral prosthesis can be designed according to the analyzed measured data and manufactured by additive manufacturing(AM)methods.Meanwhile,the reconstructed femoral condylar surface was compared with the femoral condylar surfacein the original CT scanning data The average RMS PS distance of the reconstructed femoral condylar surface among all data was(1.10±0.18)mm,which is comparable to other statistical shape modeling methods using multiple radiographs as input data.There is a need to develop an anthropometric-based knee prosthesis for the Chinese population.Based on the anthropometry of the Chinese population,our new design fits Chinese patients better and reserves more bone volume compared with current commercial prostheses,which is an essential step toward AM for personalized knee prostheses.

The Clinical Characteristics of Combined Deep Vein Thrombosis Prophylaxis of Rivaroxaban and Mechanical Therapy after Total Knee Replacement Arthroplasty

Purpose: To investigate the clinical characteristics of combined prophylaxis of rivaroxaban (Xarelto?) and mechanical therapy (foot sole pump, antiembolism stocking) after total knee replacement arthroplasty, for prevention of deep vein thrombosis (DVT). Materials and Methods: The subjects of this study were 110 patients who underwent total knee replacement arthroplasty (TKA) between November 2011 and May 2012, and were prospectively evaluated. They consisted of 13 men (11.8%) and 97 women (88.2%) with the mean age of 68.7 years (±7.9). All of the patients received 10 mg of rivaroxaban once daily for 14 days from Day 1 postoperatively, and used an intermittent pneumatic compression (IPC) pump and compression stockings immediately after the operation. To determine the presence of postoperative DVT, clinical symptoms examination, D-dimer test, color Doppler ultrasound imaging were performed to analyze the risk factors of DVT events. Results: There were a total of 13 patients (11.8%) with DVT in the distal lower limbs among the entire 110 patients. At Day 4 after the operation, a statistically significant difference was seen only in femoral swelling of several clinical symptoms between DVT group and non-DVT group (p = 0.043). D-dimer tests showed no statistically significant difference between the two groups, however with the boundary value of 0.3 mg/L, diagnostic sensitivity, specificity, positive predictability and negative predictability were equivalent to 100%, 8.2%, 12.7% and 100%, respectively. There was no significant difference between the two groups in terms of well-known risk factors including age, gender, obesity, hypertension, diabetes, smoking, and anesthesia method, and no case of pulmonary embolism was observed. Conclusion: A combination of pharmacological therapy (rivaroxaban, Xarelto?) and mechanical therapy (foot sole pump system) after TKA is considered effective for DVT prevention.

Early Clinical and Functional Outcome of Primary Total Knee Replacement with Posterior Cruciate Substituting Prosthesis for Primary Knee Osteoarthritis Using 2011 Knee Society Score

Background: Primary knee Osteoarthritis (OA) is the commonest articular disease in middle age and elderly people. Primary total knee replacement (TKR) is a known world-wide standard and definitive treatment of primary knee OA following failed adequate non-operative management. It is of clinical importance to assess the clinical and functional outcome of TKR to prognosticate the severity of primary knee OA. The new (2011) knee society scoring system (nKSS) is both surgeons and patients’ assessment tool for the treatment outcome of TKR. Study Design: Prospective interventional analytical study. Aim and Objective: The aim of the study was to determine early clinical and functional outcome of primary total knee replacement in patients with primary knee osteoarthritis using nKSS. The objectives were: 1) To determine the pre-operative nKSS and post operative nKSS;2) To determine relationships between pre-operative nKSS and post operative nKSS at 6 weeks, 3, 6, 9 and 12 months;3) To determine the complication rates in patients undergoing primary TKR in the study centre. Methods: A prospective interventional study of 59 patients aged 51 to 70 years who had 67 Total Knee Replacements (TKRs) participated in the study between November 2015 to June 2018 at National Orthopaedics Hospital, Lagos, Nigeria. Patients’ sociodemographic data, pre-operative and post-operative nKSS system were recorded at 6 weeks, 3, 6, 9 and 12 months during follow up. The data were analyzed using Statistical Package for Social Science (SPSS). Results: There were 41 females and 18 males (M:F = 1:2.3). There were total of 67 TKRs with 31 right TKRs, 20 left TKRs and 8 staged bilateral TKRs. The participants’ age ranged from 51 to 70 years with the mean age of 59.5 (±8.5) years. Four patients did not complete the study due to various reasons. The remaining 55 participants completed the study period with progressive improvement of their post-operative nKSS at 6 weeks, 3, 6, 9 and 12 months post-operatively when compared with pre-operative nKSS (P value 0.5). Conclusion: This study revealed improved early clinical and functional outcome of primary total knee replacement in primary knee osteoarthritis using nKSS in all the studied patients. There is no significant negative effect of lower pre-operative nKSS (and its components) on the post-operative nKSS outcome.

New Classification and Visual Analysis of the Patella Cartilage during Total Knee Replacement

Objective: The aim of this prospective study is to evaluate how much damage the patellar cartilage presents during a total knee replacement. Methods: The damage of the articular patellar surface was analysed by visual inspection and photographs in 354 primary total knee replacements. The authors graded the degree of cartilage lesion in five groups. The cartilage status was analyzed and correlated with age, gender, side, body mass index (BMI), Kellgren-Lawrence radiographic scale and axial deviation. Results: After statistical analysis, we concluded: there was no evidence of an association between patellar arthrosis and age gender, side, weight and deformity. Conclusions: Articular cartilage was damaged in all 354 knees. Important subchondral bone exposure occurred in 274 knees (77.4%). Obese patients had more severe patellar osteoarthritis.

Short-term outcome of total knee replacement in a patient with hemophilia:A case report and review of literature

BACKGROUND Hemophilia A is a rare inherited bleeding disorder caused by mutations in the factor Ⅷ gene. This clotting factor plays an intrinsic role in the blood coagulation pathway. Patients with hemophilia may develop orthopedic manifestations such as hemarthrosis, but multiple malunion of fractures over the knee is rare and difficult to treat.CASE SUMMARY We report a patient with hemophilia A who developed severe knee osteoarthritis along with fracture malunion and nonunion. Total knee replacement was performed using a custom-made modular hinged knee prosthesis(cemented) equipped with extended distal and proximal stems. At 3 years’ follow-up, the patient exhibited excellent clinical function and remained satisfied with the surgical outcome. Surgical intervention was accompanied by rigorous coagulation factor replacement.CONCLUSION This case highlights various unique scenarios specific to individuals with hemophilia and fracture deformity.

Role of negative pressure wound therapy in total hip and knee arthroplasty

Negative-pressure wound therapy(NPWT) has been a successful modality of wound management which is in widespread use in several surgical fields. The main mechanisms of action thought to play a role in enhancing wound healing and preventing surgical site infection are macrodeformation and microdeformation of the wound bed, fluid removal, and stabilization of the wound environment. Due to the devastating consequences of infection in the setting of joint arthroplasty, there has been some interest in the use of NPWT following total hip arthroplasty and total knee arthroplasty. However, there is still a scarcity of data reporting on the use of NPWT within this field and most studies are limited by small sample sizes, high variability of clinical settings and end-points. There is little evidence to support the use of NPWT as an adjunctive treatment for surgical wound drainage, and for this reason surgical intervention should not be delayed when indicated. The prophylactic use of NPWT after arthroplasty in patients that are at high risk for postoperative wound drainage appears to have the strongest clinical evidence. Several clinical trialsincluding single-use NPWT devices for this purpose are currently in progress and this may soon be incorporated in clinical guidelines as a mean to prevent periprosthetic joint infections.

Total knee arthroplasty:Effect of obesity and other patients' characteristics on operative duration and outcome

AIM: To examine the effects of patients' characteristics mainly obesity on operative duration and other outcomemeasures of knee arthroplasty. METHODS: This is a retrospective chart review of 204 patients who had knee arthroplasty within the past five years(2007-2011) at King Abdulaziz Medical City in Riyadh, Kingdom of Saudi Arabia. The data collection form was developed utilizing the literature review to gather all the needed variables. Data were gathered from admission notes, nursing notes, operative reports and discharge summaries.RESULTS: A feasible sample of 204 patients were included in the study. Of those patients, 155(76%) were females. The mean age was 70.1 years for males(SD ± 9.4) and 62.7 years(SD ± 8) for females. Regarding the type of total knee replacement(TKR), 163(79.9%) patients had unilateral TKR and 41(20.1%) had bilateral TKR. Nine patients(4.4%) had a normal body mass index(BMI)(18.5 to < 25). Overweight patients(BMI 25 to < 30) represented 18.1%. Obesity class Ⅰ(BMI 30 to < 35) and obesity class Ⅱ(BMI from 35 to < 40) were present in 23% and 29.9% of the patients, respectively. Morbid obesity(BMI greater than 40) was present in 24.5%. The mean duration of surgery was 126.3 min(SD ± 30.8) for unilateral TKR and 216.6 min(SD ± 55.4) for bilateral TKR.The mean length of stay in the hospital was 12 d(SD ± 4.9). The complications that patients had after the operation included 2 patients(1%) who developed deep venous thrombosis, 2 patients(1%) developed surgical wound infections and none had pulmonary embolism. Patients' characteristics(including age, gender, BMI and co-morbidities) did not have an effect on the operative duration of knee replacement nor the length of hospital stay. CONCLUSION: Our study shows that obesity and other patients' characteristics do not have effect on the operative duration nor the length of hospital stay following TKR.

A Comparison of Patient Outcomes Following Prosthetic Knee Replacement Using a Variety of Knee Prosthesis: A Ten-Year Study

There are several prosthetic knee designs currently in use. There are however very few studies comparing long-term functional outcomes between patients using different models of knee pros-thesis in elective knee replacement. In this study, we used the validated Oxford Knee Score (OKS) to retrospectively compare the outcomes of a total of 1635 patients who had an elective total knee replacement in a large District General Hospital, using fifteen different models of knee prosthesis, over a ten-year period. The average scores reported by all patient groups showed significant improvement by three months post-operatively (pre-operative mean score 15.8, post-operative mean score 39.4, p < 0.05), and remained similar for all models of prosthesis used over the total ten-year period. Based on the OKS as an assessment tool, we report no significant difference in long-term functional outcomes for this group of patients following an elective knee replacement, regardless of the type of prosthesis used.

The impact of individualized care after artificial knee replacement surgery for patients with valgus deformity of the knee

Objective:To evaluate the perioperative nursing of total knee arthroplasty for patients with valgus deformity of the knee.Methods:Seventy-six patients who underwent surgical treatment were enrolled in the study from March 2014 to March 2018.The patients in the control group were treated with routine nursing.The experimental group was treated not only with routine nursing but also with health education,psychological care,family social support,and other nursing intervention.Hospital for special surgery and Pittsburgh sleep quality index were used to evaluate the effect of nursing intervention on patients after operation.Results:All the index scores of the experimental group were lower than those of the control group(P<0.05),indicating that the function of the diseased limb and the patient's sleep status improved significantly after the intervention.Conclusions:Individualized nursing can improve the recovery of limb function and improve the patients'quality of life.It is very effective for nurses to implement individualized nursing measures for patients after surgery.

Shock-wave impact on the knee joint affected with osteoarthritis and after arthroplasty

Degenerative diseases significantly reduce the quality of human life.Non-invasive treatments are used in the initial stages of osteoarthritis(OA).Total knee arthroplasty is used in the late stages of osteoarthritis of the knee joint.Non-invasive methods based on mechanical action are also used for the rehabilitation of a patient after arthroplasty.This paper presents numerical models of the knee joint with degenerative OA changes and arthroplasty.Using these models,a computational study was made of the influence of the intensity of shock-wave exposure on the conditioning for the regeneration of bone and cartilage tissues.Based on the modeling results,it was found that in the knee joint with degenerative OA changes,conditions for the regeneration of cartilage and meniscus tissues were fulfilled under medium and highintensity loading.Under high-intensity loading(up to 0.9 m J/mm^(2)),the stress level was significantly below the ultimate value required for fracture.At knee arthroplasty,the conditions for bone tissue regeneration around the tibia component are fulfilled only under high-intensity loading.

Knee biomechanics of patients with total knee replacement during downhill walking on different slopes

Purpose:The purpose of this study was to compare knee biomechanics of the replaced limb to the non-replaced limb of total knee replacement(TKR)patients and healthy controls during walking on level ground and on decline surfaces of 5°,10°,and 15°.Methods:Twenty-five TKR patients and 10 healthy controls performed 5 walking trials on different decline slopes on a force platform and an instrumented ramp system.Two analyses of variance,2×2(limb×group)and 2×4(limb×decline slope),were used to examine selected biomechanics variables.Results:The replaced limb of TKR patients had lower peak loading-response and push-off knee extension moment than the non-replaced and the matched limb of healthy controls.No differences were found in loading-response and push-off knee internal abduction moments among replaced,non-replaced,and matched limb of healthy controls.The knee flexion range of motion,peak loading-response vertical ground reaction force,and peak knee extension moment increased across all slope comparisons between 0°and 15°in both the replaced and non-replaced limb of TKR patients.Conclusion:Downhill walking may not be appropriate to include in early stage rehabilitation exercise protocols for TKR patients.

Effect of body mass index on functional outcome in primary total knee arthroplasty——a single institution analysis of 2180 primary total knee replacements

AIM To evaluate the effect of body mass index(BMI) on short-term functional outcome and complications in primary total knee arthroplasty. METHODS All patients undergoing primary total knee arthroplasty at a single institution between 2007 and 2013 were identified from a prospective arthroplasty database. 2180 patients were included in the study. Age, gender, BMI, pre- and post-operative functional scores [Western Ontario and Mc Master University Arthritis Index(WOMAC) and SF-36], complications and revision rate were recorded. Patients were grouped according to the WHO BMI classification. The functional outcome of the normal weight cohort(BMI < 25) was compared to the overweight and obese(BMI ≥ 25) cohort. A separate sub-group analysis was performed comparing all five WHO BMI groups; Normal weight, overweight, class 1 obese, class 2 obese and class 3 obese.RESULTS With a mean age of 67.89(28-92), 2180 primary total knee replacements were included. 64.36%(1403) were female. The mean BMI was 31.86(18-52). Ninty-three percent of patients were either overweight or obese. Mean follow-up 19.33 mo(6-60 mo). There was no significant difference in pre or post-operative WOMAC score in the normal weight(BMI < 25) cohort compared to patients with a BMI ≥ 25(P > 0.05). Sub-group analysis revealed significantly worse WOMAC scores in class 2 obese 30.80 compared to overweight 25.80(P < 0.01) and class 1 obese 25.50(P < 0.01). Similarly, there were significantly worse SF-36 scores in class 2 obese 58.16 compared to overweight 63.93(P < 0.01) and class 1 obese 63.65(P < 0.01) There were 32(1.47%) superficial infections, 9(0.41%) deep infections and 19(0.87%) revisions overall with no complications or revisions in the normal weight cohort(BMI < 25).CONCLUSION Post-operative functional outcome was not influenced by BMI comparing normal weight individuals with BMI > 25. Patients should not be denied total knee arthroplasty based solely on weight alone.

Analysis of Factors Influencing True Blood Loss in Navigated Total Knee Replacements

Title: Analysis of factors influencing true blood loss in navigated total knee replacements. Objectives: To evaluate true blood loss in total knee replacements and analyze the various factors such as gender, BMI, diagnosis, size of implants, duration of surgery, tourniquet usage etc. on calculated blood loss using formula by Nadler et al. All the cases included have been done using navigation system and no comparison with conventional jig based surgeries has been attempted. Methods: Retrospectively data of primary cemented total knee replacements performed from October 2012 to August 2013 were evaluated. All surgeries were performed using navigation system. The data collected included patient sex, height, weight and preoperative haemoglobin and hematocrit. The patients’ postoperative data of haemoglobin, hematocrit and drains were collected. All patients had their CBC done on 2nd post operative day. Any data on transfusions that patients received were also collected. We also collected data regarding the size of implant used. We calculated true blood based on formula given by Nadler, Hidalgo & Bloch. We excluded patients whose data were incomplete or who received tranexamic acid. Patients who needed stems (femoral or tibial) were also excluded from this study. Results: The average true calculated blood loss was 959.44 ml. BMI did not have any effect on blood loss. But larger size implants were associated with more blood loss. Conclusion: The preoperative haemoglobin is one of the most important factors in determining transfusion following the knee replacement. Male gender and larger implants are associated with more blood loss. BMI, diagnosis of OA or RA, tourniquet usage and time have no significant effect on blood loss. Our calculated blood loss compares favourably with published literature.

Perioperative blood management strategies for patients undergoing total knee replacement:Where do we stand now?

Total knee replacement(TKR) is one of the most common surgeries over the last decade. Patients undergoing TKR are at high risk for postoperative anemia and furthermore for allogeneic blood transfusions(ABT). Complications associated with ABT including chills, rigor, fever, dyspnea, light-headedness should be early recognized in order to lead to a better prognosis. Therefore, perioperative blood management program should be adopted with main aim to reduce the risk of blood transfusion while maximizing hemoglobin simultaneously. Many blood conservation strategies have been attempted including preoperative autologous blood donation, acute normovolemic haemodilution, autologous blood transfusion, intraoperative cell saver, drain clamping, pneumatic tourniquet application, and the use of tranexamic acid. For practical and clinical reasons we will try to classify these strategies in three main stages/pillars: Pre-operative optimization, intra-operative and post-operative protocols. The aim of this work is review the strategies currently in use and reports our experience regarding the perioperative blood management strategies in TKR.

Common controversies in total knee replacement surgery: Current evidence

Total knee replacement(TKR) is a widely used operation that has radically improved the quality of life of millions of people during the last few decades. However, some technical details, concerning the surgical procedure and the rehabilitation following total knee arthroplasty, are still a matter of a strong debate. In this review of the literature, we have included the best evidence available of the last decade, in an effort to shed light on some of the most controversial subjects related to TKR surgery. Posterior-stabilized or cruciate-retaining prosthesis? To use a tourniquet during operation or not? Do patients need continuous passive motion for their post-surgery rehabilitation? To resurface patella or not? These are some of the most controversial topics that until now have been persistent dilemmas for the orthopedic surgeon. Results of this systematic review of the literature are highly controversial. These conflicting results are an indication that larger and more well conducted high quality trials are needed in order to gain more secure answers. At the same time, it is becoming apparent that a meticulous operative technique, respecting the soft tissue envelope and knowing the principles of alignment and soft tissue balancing, aresome of the parameters that might contribute more to achieving the optimal results for the patients.

Persistent post-surgical pain and neuropathic pain after total knee replacement

AIM: To study the prevalence of persistent post-surgical pain(PPSP) and neuropathic pain(NP) after total knee replacement(TKR).METHODS: MEDLINE and Embase databases were searched for articles published until December 2014 in English language. Published articles were included if they referred to pain that lasts at least 3 mo after primary TKR for knee osteoarthritis, and measured pain with pain specific instruments. Studies that referred to pain caused by septic reasons and implant malalignment were excluded. Both prospective and retrospective studies were included and only 14 studies that match the inclusion criteria were selected for this review.RESULTS: The included studies were characterized by the heterogeneity on the scales used to measure pain and pre-operative factors related to PPSP and NP. The reported prevalence of PPSP and NP seems to be relatively high, but it varies among different studies. There is also evidence that the prevalence of post-surgical pain is related to the scale used for pain measurement. The prevalence of PPSP is ranging at 6 mo from 16% to 39% and at 12 mo from 13.1% to 23% and even 38% of the patients. The prevalence of NP at 6 mo post-operatively is ranging from 5.2% to13%. Pre-operative factors related to the development of PPSP also differ, including emotional functioning, such as depression and pain catastrophizing, number of comorbidities, pain problems elsewhere and operations in knees with early grade of osteoarthritis.CONCLUSION: No firm conclusions can be reached regarding the prevalence of PPSP and NP and the related factors due to the heterogeneity of the studies.