Psychological determinants of problematic outcomes following Total Knee Arthroplasty The role of presurgical expectancies in predicting pain and function one year following total knee arthroplasty Prospective relation between catastrophizing and residual pain following knee arthroplasty: two-year follow-up. Are psychological predictors of chronic postsurgical pain dependent on the surgical model? A comparison of total knee arthroplasty and breast surgery for cancer. Prediction of postoperative pain by preoperative pain response to heat stimulation in total knee arthroplasty Local infiltration anesthesia with steroids in total knee arthroplasty: A systematic review of randomized control trials. Preoperative predictors of pain following total knee arthroplasty. Quadriceps strength and the time course of functional recovery after total knee arthroplasty. Catastrophizing and depressive symptoms as prospective predictors of outcomes following total knee replacement. Minimally invasive total knee arthroplasty: surgical implications for recovery. Fast-track hip and knee replacement — what are the issues? Pain and Recovery After Total Knee Arthroplasty: A 12-Month Follow-up After a Prospective Randomized Study Evaluating Nefopam and Ketamine for Early Rehabilitation Knee pain during the first three months after unilateral total knee arthroplasty: a multi-centre prospective cohort study. Patellar denervation in total knee arthroplasty without patellar resurfacing: a prospective, randomized controlled study. Effect of pulsed electromagnetic field therapy in patients undergoing total knee arthroplasty: a randomised controlled trial Comparison of quadriceps-sparing minimally invasive and medial parapatellar total knee arthroplasty: a 2-year follow-up study.
ABSTRACT The primary objective of the present study was to examine the role of pain‐related psychological factors in predicting pain and disability following Total Knee Arthroplasty ( TKA ) . The study sample consisted of 75 ( 46 women , 29 men ) individuals with osteoarthritis of the knee who were scheduled for TKA .  Measures of pain severity , pain catastrophizing , depression , and pain‐related fears of movement  were completed prior to surgery . Participants completed measures of pain severity and self‐reported disability 6 weeks following surgery . Consistent with previous research , cross‐sectional analyses revealed significant correlations among measures of pre‐surgical pain severity , pain catastrophizing , depression and pain‐related fears of movement . Prospect i ve analyses revealed that pre‐surgical pain severity and pain catastrophizing were unique predictors of post‐surgical pain severity ( 6‐week follow‐up ) . Pain‐related fears of movement were predictors of post‐surgical functional difficulties in univariate analyses , but not when controlling for pre‐surgical co‐morbidities ( e.g. back pain ) . The results of this study add to a growing literature highlighting the prognostic value of psychological variables in the prediction of post‐surgical health outcomes . The results support the view that the psychological determinants of post‐surgical pain severity differ from the psychological determinants of post‐surgical disability . The results suggest that interventions design ed to specifically target pain‐related psychological risk factors might improve post‐surgical outcomes Summary Patients ’ behavioral outcome expectancies assessed presurgically predicted pain severity and physical function 1 year after total knee arthroplasty ( TKA ) and partially mediated the relation between catastrophizing and TKA outcomes . Abstract The present study examined the prospect i ve value of response expectancies ( ie , pain , sleep ) and behavioral outcome expectancies ( ie , return to function ) in the prediction of pain severity and functional limitations 12 months after total knee arthroplasty ( TKA ) . The study sample consisted of 120 individuals ( 73 women , 47 men ) with osteoarthritis of the knee who were scheduled for TKA .  Measures of expectancies , pain severity , pain catastrophizing , pain‐related fears of movement , and depression  were completed prior to surgery . Participants also completed measures of pain severity and functional limitations 12 months following surgery . Analyses revealed that behavioral outcome expectancies were stronger predictors of follow‐up pain and functional limitations than response expectancies . Consistent with previous research , analyses also revealed that pain catastrophizing , pain‐related fear of movement , and depression predicted follow‐up pain and function . In a multivariate analysis , only pain catastrophizing contributed significant unique variance to the prediction of follow‐up pain and function . Behavioral outcome expectancies partially mediated the relation between catastrophizing and follow‐up pain and function . The relation between catastrophizing and follow‐up pain severity and functional limitations remained significant even when controlling for behavioral outcome expectancies . The results suggest that interventions design ed to specifically target behavioral outcome expectancies and catastrophizing might improve post‐surgical outcomes BACKGROUND Pain is the primary indication for both primary and revision total knee arthroplasty ( TKA ) ; however , most arthroplasty outcome measures do not take pain into account . OBJECTIVE To document the prospect i ve pain experience following TKA , with subjective pain-specific question naires to determine if comorbidities , preoperative pain or preoperative pain catastrophizing scores are predictive of long-term pain outcomes . METHODS Fifty-five patients with a primary diagnosis of osteoarthritis of the knee , who were scheduled to undergo TKA , were asked to fill out the McGill Pain Question naire ( MPQ ) and the Pain Catastrophizing Scale ( PCS ) preoperatively and at three , 12 and 24 months follow-up . Comorbidities were extracted from the Queen Elizabeth II Health Sciences Centre health information system . RESULTS The overall response rate ( return of completed question naires ) was 84 % . There was a significant decrease in the MPQ scores ( P<0.05 ) postoperatively . PCS scores did not change over time . Receiver operating characteristic curves revealed the number of comorbidities per patient predicted the presence of pain postoperatively , as documented by the numerical rating subscale of the MPQ at 24 months ( P<0.05 ) . Receiver operating characteristic curves for preoperative PCS and rumination subscale scores predicted the presence of pain , as measured by the Pain Rating Index subscale of the MPQ at 24 months ( P<0.05 ) . Preoperative PCS scores and comorbidities were significantly higher in the persistent pain group ( P<0.05 ) . CONCLUSIONS The number of comorbidities predicted the presence of pain at 24 months follow-up and , for the first time , preoperative PCS scores were shown to predict chronic postoperative pain . This may enable the identification of knee arthroplasty patients at risk for persistent postoperative pain , thus allowing for efficient administration of preoperative interventions to improve arthroplasty outcomes UNLABELLED Anxiety , depression , and catastrophizing are generally considered to be predictive of chronic postoperative pain , but this may not be the case after all types of surgery , raising the possibility that the results depend on the surgical model . We assessed the predictive value of these factors for chronic postsurgical pain in 2 different surgical models : total knee arthroplasty for osteoarthritis ( 89 patients , 65 % women , age = 69 ± 9 years , baseline pain intensity = 4.7 ± 2.1 ) and breast surgery for cancer ( 100 patients , 100 % women , age = 55 ± 12 years , no preoperative pain ) . Data were collected before surgery , then 2 days and 3 months after surgery . Anxiety , depression , and catastrophizing were measured with the Spielberger State-Trait Anxiety Inventory , Beck Depression Inventory , and Pain Catastrophizing Scale , respectively . Pain was assessed with the  Brief Pain Inventory  . Neuropathic pain was detected with the DN4 question naire . Multivariate logistic regression analyses for the total knee arthroplasty and breast surgery models considered together indicated that the presence of clinical ly meaningful chronic pain at 3 months ( pain intensity ≥3/10 ) was predicted independently by age ( P = .04 ) , pain intensity on day 2 ( P = .009 ) , and state anxiety ( P = .001 ) . Linear regression models also showed that pain magnification , one of the dimensions of catastrophizing , independently predicted chronic pain intensity ( P = .04 ) . These results were not affected by the surgical model or by the neuropathic characteristics of the pain . Thus , state anxiety and pain magnification seem to constitute psychological risk factors for chronic postsurgical pain relevant in all surgical models . PERSPECTIVE This prospect i ve study performed in patients with total knee arthroplasty or breast surgery for cancer shows that state anxiety , amplification of pain , and acute postoperative pain independently predict postsurgical pain at 3 months and that this does not depend on the surgical model Summary Pain responses to 2 types of preoperative heat stimuli were not independent clinical ly relevant predictors for postoperative pain after total knee arthroplasty . ABSTRACT It has been estimated that up to 54 % of the variance in postoperative pain experience may be predicted with preoperative pain responses to experimental stimuli , with suprathreshold heat pain as the most consistent test modality . This study aim ed to explore whether 2 heat test paradigms could predict postoperative pain  after total knee arthroplasty ( TKA ) . Patients scheduled for elective , unilateral , primary TKA under spinal anesthesia were consecutively included in this prospect i ve , observational study . Perioperative analgesia was st and ardized for all patients . Outcomes were postoperative pain during walk : from 6 to 24 hours ( primary ) , from postoperative day ( POD ) 1 to 7 ( secondary ) , and from POD 14 to 30 ( tertiary ) . Two preoperative tonic heat stimuli with 47 ° C were used ; short ( 5 seconds ) and long ( 7 minutes ) stimulation upon which patients rated their pain response on an electronic visual analog scale . Multivariate stepwise linear and logistic regressions analyses were carried out , including 8 potential preoperative explanatory variables ( among these anxiety , depression , preoperative pain , and pain catastrophizing ) to assess pain response to preoperative heat pain stimulation as an independent predictor for postoperative pain . A total of 100 patients were included , and 3 were later excluded . A weak correlation [ rho ( 95 % confidence interval ) ; P value ] was observed between pain from POD 1 to 7 and pain response to short [ rho = 0.25(0.04 to 0.44 ) ; P = .02 ] and to long [ rho = 0.27 ( 0.07 to 0.46 ) ; P = .01 ] heat pain stimulation . However , these positive correlations were not supported by the linear and logistic regression analyses , in which only anxiety , preoperative pain , and pain catastrophizing were significant explanatory variables ( but with low R‐squares ; 0.05 to 0.08 ) . Pain responses to 2 types of preoperative heat stimuli were not independent clinical ly relevant predictors for postoperative pain after TKA Local infiltration anesthesia ( LIA ) with anesthetics , steroids , NSAIDS , and epinephrine has been shown to be effective in reducing total knee arthroplasty ( TKA ) postoperative pain . This systematic review explores the functional outcomes of r and omized control trials that have compared the use of LIA with and without steroids during TKA . Five studies with 412 patients met the inclusion criteria , 228 received local infiltration anesthesia with steroids ( LIAS ) and 184 received local infiltration anesthesia without steroids ( LIAWS ) . The use of LIAS in management of postoperative TKA pain has been shown to decrease the length of hospital stay , time required to achieve straight leg raise , and pro-inflammatory signals in patients . Although there is no overwhelming data to suggest LIAS  improves postoperative TKA pain , current literature does support its effectiveness in producing other favorable surgical outcomes Total knee arthroplasty has provided dramatic improvements in function and pain for the majority of patients with knee arthritis , yet a significant proportion of patients remain dissatisfied with their results . We performed a prospect i ve analysis of 215 patients undergoing TKA who underwent a comprehensive array of evaluations to discover whether any preoperative assessment could predict high pain scores and functional limitations postoperatively . Patients with severe pain with a simple knee range-of-motion test prior to TKA had a 10 times higher likelihood of moderate to severe pain at 6 months . A simple test of pain intensity with active flexion and extension preoperatively was a significant predictor of postoperative pain at 6 months after surgery . Strategies to address this particular patient group may improve satisfaction rates of TKA STUDY DESIGN Prospect i ve study with repeated measures . OBJECTIVES The overall goal of this investigation was to describe the time course of recovery of impairments and function after total knee arthroplasty ( TKA ) , as well as to provide direction for rehabilitation efforts . We hypothesized that quadriceps strength would be more strongly correlated with functional performance than knee flexion range of motion ( ROM ) or pain at all time periods studied before and after TKA . BACKGROUND TKA is a very common surgery , but very little is known regarding the influence of impairments on functional limitations in this population . METHODS AND MEASURES Forty subjects who underwent unilateral TKA followed by rehabilitation , including 6 weeks of outpatient physical therapy , were studied . Testing occurred at 5 time periods : preoperatively , and at 1 , 2 , 3 , and 6 months after surgery . Test measures included  quadriceps strength , knee ROM , timed up- and -go test , timed stair-climbing test , bodily pain , and general health and knee function question naires . RESULTS Subjects experienced significant worsening of knee ROM , quadriceps strength , and performance on functional tests 1 month after surgery . Quadriceps strength went through the greatest decline of all the physical measures assessed and never matched the strength of the uninvolved limb . All measures underwent significant improvements following the 1-month test . Quadriceps strength was the most highly correlated measure associated with functional performance at all testing sessions . CONCLUSIONS Functional measures underwent an expected decline early after TKA , but recovery was more rapid than anticipated and long-term outcomes were better than previously reported in the literature . The high correlation between quadriceps strength and functional performance suggests that improved postoperative quadriceps strengthening could be important to enhance the potential benefits of TKA Several recent reports suggest that pain-related catastrophizing  is a risk factor for poor acute pain outcomes following surgical interventions . However , it has been less clear whether levels of catastrophizing influence longer-term postoperative outcomes . Data were analyzed from a relatively small number ( n=43 ) of patients who underwent total knee replacement and were followed for 12 months after their surgery . Previous research has suggested that high levels of both catastrophizing and depression are associated with elevated acute postoperative pain complaints among patients undergoing knee surgery . In this sample ,  catastrophizing and depression at each of the assessment points were studied as prospect i ve predictors of pain ( both global pain ratings and pain at night ) at the subsequent assessment point over the course of one year . The predictive patterns differed somewhat across measures of pain reporting ; depressive symptoms were unique predictors of greater global pain complaints , while catastrophizing was a specific and unique predictor of elevated nighttime pain . While surgical outcomes following total knee replacement are , on average , quite good , a significant minority of patients continue to experience long-term pain . The present findings suggest that high levels of catastrophizing and depression may promote enhanced pain levels , indicating that interventions design ed to reduce catastrophizing and depressive symptoms may have the potential to further improve joint replacement outcomes BACKGROUND Despite growing interest in minimally invasive surgery ( MIS ) techniques for total knee arthroplasty ( TKA ) , few r and omized controlled trials have compared MIS and conventional TKA using a combination of functional performance , knee pain , knee range of motion ( ROM ) , and surgical and radiographic outcomes . METHODS A prospect i ve , r and omized investigation comparing early outcomes of TKA using conventional or MIS approaches  ( n = 44 ) . Patients were assessed preoperatively , 48 hours , 4 and 12 weeks postoperatively by blinded evaluators . Outcome measures included timed-up- and -go , 100-ft walk , knee pain , passive knee ROM , Knee Society Score , blood loss , tourniquet time , hospital length of stay , surgical complications , and radiographic outcomes . RESULTS No significant differences in functional performance , knee pain , knee ROM , surgical , or radiographic outcomes were observed between groups at 48 hours , 4 or 12 weeks postoperatively . CONCLUSION While surgical and radiographic outcomes were not compromised with MIS surgery , there were also no improvements in pain , ROM , or functional performance with MIS TKA Surgical injury is followed by pain , stress-induced catabolism , impairment of organ function , and a risk of thromboembolism and impaired cognitive function . These events may contribute to complications , a need for prolonged hospitalization , postoperative fatigue , delayed convalescence , and the need for rehabilitation . Optimization of the individual care components in perioperative care ( the fast-track methodology ) reduces the need for hospitalization , morbidity , and prolonged convalescence , with subsequent economic savings ( Kehlet and Wilmore 2008 ) . Correspondingly , improvement in perioperative care has led to a reduced stay in hospital after total hip arthroplasty ( THA ) and total knee arthroplasty ( TKA ) , which is now only about 3 days in many centers . The main question that remains to be answered is whether further improvement can be made and whether these operations can be performed on an ambulatory or semi-ambulatory basis without any increased risk of morbidity or cardiopulmonary and thromboembolic complications , long-term cognitive dysfunction , pain , and need for rehabilitation . Thus , a multidisciplinary collaboration has been established in 5 dedicated public Danish hospitals with established fast-track THA and TKA in order to optimize perioperative care to require only 1–2 days of hospitalization with no increase in post-discharge pain , morbidity , and rehabilitation requirements ( Figure ) . To this end , we concentrated on  perioperative pain management , optimization of transfusion strategies , strategies for postoperative rehabilitation , requirements for postoperative thromboembolic prophylaxis , and safety aspects ( re-admissions , hip dislocation , and knee stiffness ) . Effective postoperative pain relief is a prerequisite for a successful fast-track recovery . Although continuous peripheral nerve blocks are currently the most effective analgesic techniques ( Ilfeld et al. 2008a , b ) , they are dem and ing in terms of expertise and there is a risk of muscle paralysis . Efforts have therefore been made recently to improve local wound infiltration and infusion techniques . Although promising , more research is required to better define these techniques regarding dose-volume relationships , placement and types of catheters , duration , and safety aspects ( Rostlund and Kehlet 2007 ) . There will be more focus on post-discharge pain , which remains a problem in many patients . Furthermore , research will concentrate on mechanisms and predictors of the large inter-individual variability in the degree of postoperative pain , which may be related to the inflammatory response and genes associated with pain . Such knowledge should facilitate pain management , leading to differential use of analgesic principles in low pain responders and high-pain responders . Blood transfusion is indicated when a patient 's limit concerning — or physiological adaptation to — progressive normovolemic anemia is reached , but there are no specific data from THA and TKA . Data from hip fracture surgery have shown that postoperative anemia impedes functional mobility and that a liberal transfusion strategy reduces morbidity ( Foss et al. 2009 ) . Since modern blood transfusion is safer than before , large r and omized studies with high and low transfusion thresholds will be performed in cardiovascular high-risk patients after THA , with morbidity and functional recovery as primary outcome measures . Postoperative rehabilitation after THA and TKA has been st and ard despite the fact that there has been little evidence on the optimal type of physiotherapy , when it should be started , and for how long ( Minns Lowe et al. 2007 , 2009 ) . Previous r and omized studies have been inconclusive and they were based on relatively long-term hospitalization ( 7–12 days ) ; they are therefore not applicable to fast-track THA and TKA . Over the last decade , many industry-sponsored trials have documented the need for prolonged thromboembolic prophylaxis ( 10–30 days ) , mostly based on surrogate outcomes and with relatively small effects on clinical manifestations of thromboembolism ( Geerts et al. 2008 ) . A common characteristic of these studies has been a relatively long hospital stay ( 6–12 days or more ) . Since postoperative immobilization is a well-known risk factor for postoperative thromboembolism , the need for prolonged thromboembolic prophylaxis after implementation of fast-track surgery with early mobilization might be question ed . The fast-track group will therefore focus on a large ( n = 5,000 ) prospect i ve , detailed 90-day follow-up study with prophylaxis only until discharge ( 1–3 days ) . It is well-documented that cognitive function declines after THA and TKA in elderly patients ( Maze et al. 2008 ) . A fast-track setup may reduce cognitive dysfunction due to less postoperative sleep disturbances , less pain , and less opioid requirements , all of which may impair cognitive function . Finally , in the fast-track THA and TKA setting , safety aspects will be assessed regarding the risk of hip dislocation , and knee stiffness after TKA . In summary , despite major improvements in care and short-term outcome after THA and TKA , several issues remain to be answered in order to optimize fast-track treatment Objectives : Ketamine and nefopam has been documented to decrease pain intensity and improve rehabilitation after total knee arthroplasty ( TKA ) . We conducted a follow-up study of a previously r and omized clinical trial to determine the prevalence and risk factors of chronic pain 1 year after TKA and to assess the role of perioperative administration of ketamine and nefopam . Material s and Methods : The original r and omized , double-blind trial evaluated postoperative pain in 75 patients scheduled for TKA who received either a 48-hour infusion of ketamine or nefopam compared with placebo . The current study has evaluated patients at 6 and 12 months for the presence of chronic pain defined as a visual analogue scale ≥40 mm during a stair-climbing test . Other outcomes were incidence of neuropathic pain evaluated ( DN4 score ) , active flexion of the knee , and functional outcome ( KOOS-PS score ) . Results : A total of 69 patients completed the trial .  The prevalence of chronic pain at 12 months was 17.4 % ( 95 % confidence interval [ CI ] , 10.2%-27.9 % ) without difference between the ketamine ( 12.5 % ) , nefopam ( 13.7 % ) , and placebo groups ( 26.1 % ) . Prevalence of neuropathic pain was 10.2 % ( 95 % CI , 3%-17.3 % ) . Ketamine  reduced DN4 scores ( P=0.02 ) , increased knee flexion ( P=0.0007 ) , and KOOS-PS scores ( P<0.0001 ) compared with placebo . A visual analogue scale score ≥60 mm in the postoperative period was the only risk factor associated with the occurrence of chronic pain ( odds ratio 4.54 ; 95 % CI , 1.17 - 17.67 ) . Discussion : After TKA , the intensity of postoperative pain is a risk factor of chronic pain on movement . Intraoperative ketamine seems to improve long-term results of rehabilitation in this setting Many patients have an unfavourable pain outcome post total knee arthroplasty ( TKA ) . This multi-centre prospect i ve cohort study recorded weekly pain scores one week before TKA and 12 weeks post TKA . 96 patients were enrolled into the study . Patients kept a record of their weekly scores pre-operation and post-operation by using the visual acuity score . Pain was divided into " best " pain score ( lowest pain score ) and " worst " pain score ( highest pain score ) . Patients with a pre-operative pain scores ≤ 4 were identified as an at risk group for poor pain outcome . Female gender , age and anaesthetics type were not identified as risk factors for poor pain outcome . Pain trajectory analysis also identified general patterns of pain response post TKA BACKGROUND Anterior knee pain is still a major problem in total knee arthroplasty ( TKA ) . Although the most widely accepted opinion is that anterior knee pain is often associated with a patellofemoral etiology , there is no clear consensus as to etiology or treatment . Disabling pain receptors by electrocautery could theoretically achieve denervation of the anterior knee region . The present prospect i ve r and omized controlled study aim ed to evaluate results after patellar denervation with electrocautery in TKA at a minimum follow-up of 2 years . HYPOTHESIS Patellar denervation provides some benefit in terms of pain and clinical outcomes after TKA without patellar resurfacing . PATIENTS AND METHODS Clinical and radiological results for 35 patients with single-stage bilateral TKA ( 70 knees ; 26 women , nine men ; mean age , 68 years [ range , 58 to 77 years ] ) were review ed . In addition to removal of all osteophytes , patellar denervation by electrocautery was performed on one patella ; and debridement alone , removing all osteophytes , was performed on the contralateral patella , as a control . KSS score and a visual analog scale ( VAS ) were used to assess pre- and postoperative anterior knee pain . RESULTS Mean follow-up was 36 months ( 24 to 60 months ) . No revisions or re-operations were performed . There were no patellar fractures . On all parameters ( KSS score , range of motion and VAS ) , there was a statistically significant pre- to postoperative difference in favor of the denervation group . DISCUSSION Patellar denervation with electrocautery can reduce anterior knee pain , with satisfactory clinical and radiological outcome , in TKA without patellar resurfacing . LEVEL OF EVIDENCE Level II : low-powered prospect i ve r and omized trial Purpose It has been reported that even one year after total knee arthroplasty ( TKA ) , a relevant percentage of patients does not attain complete recovery and indicate unfavourable long-term pain outcome . We compared the clinical outcome of 33 patients undergoing TKA r and omly assigned to the control or the pulsed electromagnetic field group ( I-ONE therapy ) .  Methods I-ONE therapy was administered postoperatively four hours per day for 60 days . Patients were assessed before surgery and then at one , two and six months postoperatively using international scores . Results One month after TKA , pain , knee swelling and functional score were significantly better in the treated compared with the control group . Pain was still significantly lower in the treated group at the six month follow-up . Three years after surgery , severe pain and occasional walking limitations were reported in a significantly lower number of patients in the treated group . Conclusions Advantages deriving from early control of joint inflammation may explain the maintenance of results at follow-up . I-ONE therapy should be considered an effective completion of the TKA procedure BACKGROUND / PURPOSE Quadriceps-sparing minimally invasive total knee arthroplasty ( TKA ) has been proposed to limit surgical dissection without compromising surgical outcome . We conducted a prospect i ve and r and omized study to compare the outcomes of patients who underwent quadriceps-sparing TKA  with the outcomes of those who underwent st and ard medial parapatellar TKA  , after a 2-year follow-up period . METHODS Eighty primary TKA procedures that were to be performed in 60 osteoarthritis patients were r and omly assigned to either a  quadriceps-sparing ( 40 knees ) or a  st and ard medial parapatellar ( 40 knees ) group . All surgeries were design ed to set the prosthesis with a femoral component alignment of 7 ° valgus and a tibial component alignment that was perpendicular to the tibial shaft . Surgical time and  tourniquet time were recorded . Outcome variables included knee function , as defined by a hospital for special surgery knee score ; quadriceps muscle strength , which was measured by an isokinetic dynamometer ; pain , as indicated on a visual analog scale ; prosthetic position , which was measured on plain radiograph ; and range of motion . RESULTS Patients who underwent the 38 quadriceps-sparing and 37 st and ard TKA  procedures completed the 2-year follow-up period without any infection or revision . The mean surgical time and tourniquet time were significantly longer in the quadriceps-sparing group . The mean peak quadriceps muscle strength , hamstring muscle strength , normalized muscle balance ( hamstring/quadriceps ratio ) , pain score , function score , and range of motion were comparable in both groups at 2 months and 2 years . In the quadriceps-sparing group , both the femoral and the tibial components were significantly more varus-deviated from the expected position . CONCLUSIONS Patients undergoing quadriceps-sparing and st and ard medial parapatellar TKA  had comparable outcomes for quadriceps muscle strength , hamstring-quadriceps balance , and knee function ; however , the quadriceps-sparing TKA was more time consuming surgically and result ed in a less accurate prosthesis position
This study provides moderate-level evidence for pain catastrophizing as an independent predictor of chronic pain post-TKA .
BACKGROUND Total knee arthroplasty ( TKA ) is a common and costly surgical procedure .
Despite high success rates , many TKA patients develop chronic pain  in the months and years following surgery , constituting a public health burden .
Pain catastrophizing is a construct that reflects anxious preoccupation with pain , inability to inhibit pain-related fears , amplification of the significance of pain vis-à-vis health implication s , and a sense of helplessness regarding pain .
Recent research suggests that it may be an important risk factor for untoward TKA outcomes .
To clarify this impact , we systematic ally review ed the literature to date on pain catastrophizing as a prospect i ve predictor of chronic pain following TKA .