***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background Total hip or knee replacement is highly successful when judged by prosthesis-related outcomes . However , some people experience long-term pain . Objectives To review published studies in representative population s with total hip or knee replacement for the treatment of osteoarthritis reporting proportions of people by pain intensity . Data sources MEDLINE and EMBASE data bases search ed to January 2011 with no language restrictions . Citations of key articles in ISI Web of Science and reference lists were checked . Study eligibility criteria , participants and interventions Prospect i ve studies of consecutive , unselected osteoarthritis patients representative of the primary total hip or knee replacement population , with intensities of patient-centred pain measured after 3 months to 5-year follow-up . Study appraisal and synthesis methods Two authors screened titles and abstract s. Data extracted by one author were checked independently against original articles by a second . For each study , the authors summarised the proportions of people with different severities of pain in the operated joint . Results Search es identified 1308 articles of which 115 reported patient-centred pain outcomes .  Fourteen articles describing 17 cohorts ( 6 with hip and 11 with knee replacement ) presented appropriate data on pain intensity . The proportion of people with an unfavourable long-term pain outcome in studies ranged from about 7 % to 23 % after hip and 10 % to 34 % after knee replacement . In the best quality studies , an unfavourable pain outcome was reported in 9 % or more of patients after hip and about 20 % of patients after knee replacement . Limitations Other studies reported mean values of pain outcomes . These and routine clinical studies are potential sources of relevant data . Conclusions and implication s of key findings After hip and knee replacement , a significant proportion of people have painful joints . There is an urgent need to improve general awareness of this possibility and to address determinants of good and bad outcomes A gait analysis system was used to evaluate the kinematics of the hip and knee during stair ascending and descending after operation with total knee replacement . Patients with 5 ° varus/valgus alignment or less were selected r and omly to receive either a flat or a concave tibial component with retention of the posterior cruciate ligament . Patients who had more than 5 ° varus/valgus alignment and /or an extension defect of 10 ° or more were selected r and omly to receive the concave or posterior-stabilized tibial component with resection of the posterior cruciate ligament .  Twenty patients and 17 controls were studied 1–2 years after the operation . Patients had abnormal kinematics during stair ascending and descending . Both knee extension and flexion were reduced . Hip extension tended to decrease , and decreased hip extension moment was noted . RésuméUn system d’analyse de la marche a été utilisé pour évaluer la cinématique de la hanche et du genou pendant la montée et la descente d’escalier après prothèse totale du genou . Les malades avec 5 ° ou moins de varus/valgus ou moins ont été r and omisés pour recevoir un composant tibial plat ou concave avec conservation du ligament croisé postérieur . Les malades qui avaient plus de 5 ° de varus/valgus et/ou un défaut d’extension de 10 ° ou plus ont été r and omisés pour recevoir un composant tibial concave ou un composant postéro-stabilisé avec résection du ligament croisé postérieur . Vingt et un malades et 17 contrôles ont été étudiés une à deux années après l’opération . Les malades avaient une cinématique anormale pendant la montée et la descente l’escalier . L’extension et flexion du genou étaient plus faibles . L’extension de la hanche avait tendance à diminuer et une augmentation du moment de flexion a été noté A cross-sectional , community-based survey of a r and om sample of 1750 of 242,311 Medicare recipients was performed . The patients were at least sixty-five years old and had had a primary or revision knee replacement ( either unilaterally or bilaterally ) between 1985 and 1989 . Three sample s were surveyed separately : a national sample ( to reflect the United States as a whole ) and sample s from Indiana and the western part of Pennsylvania ( sites chosen for convenience to assess the validity of the findings for the national sample on a regional level ) . Each sample was stratified by race , age , residence ( urban or rural ) , and the year of the procedure . Valid and reliable question naires were used to elicit the participants ' assessment s of pain , physical function , and satisfaction two to seven years after the knee replacement . Of the 1486 patients who were eligible for inclusion in the survey , 1193 ( 80.3 per cent ) responded . The mean age of the respondents was 72.6 years . Eight hundred and forty-nine respondents ( 71.2 per cent ) were white , and 849 ( 71.2 per cent ) were women . The participants reported that they had little or no pain in the knee at the time of the survey , regardless of the age at the time of the knee replacement , the body-mass index , or the length of time since the knee replacement . After adjustment for potential confounding variables , predictors of better physical function after the replacement were an absence of problems with the contralateral knee , primary knee replacement ( rather than revision ) ( Indiana sample only ) , and a lower body-mass index ( Indiana and western Pennsylvania sample s ) . Four hundred and fifteen ( 85.2 per cent ) of the 487 patients in the national sample were satisfied with the result of the knee replacement . In what we believe to be the first community-based study of the outcome of knee replacement , patients reported having significant ( p = 0.0001 ) and persistent relief of pain , improved physical function , and satisfaction with the result two to seven years postoperatively . The findings of the present study suggest that age and obesity do not have a negative impact on patient-relevant outcomes ( pain and physical function ) . Dissemination of these findings has the potential to increase appropriate referrals for knee replacement and thereby reduce the pain and functional disability due to osteoarthrosis of the knee We have developed a 12-item question naire for patients having a total knee replacement ( TKR ) . We made a prospect i ve study of 117 patients before operation and at follow-up six months later , asking them to complete the new question naire and the form SF36 . Some also filled in the Stanford Health Assessment Question naire ( HAQ ) . An orthopaedic surgeon completed the American Knee Society ( AKS ) clinical score . The single score derived from the new question naire had high internal consistency , and its reproducibility , examined by test-retest reliability , was found to be satisfactory . Its validity was established by obtaining significant correlations in the expected direction with the AKS scores and the relevant parts of the SF36 and HAQ . Sensitivity to change was assessed by analysing the differences between the preoperative scores and those at follow-up . We also compared change in scores with the patients ' retrospective judgement of change in their condition . The effect size for the new question naire compared favourably with those for the relevant parts of the SF36 . The change scores for the new knee question naire were significantly greater ( p < 0.0001 ) for patients who reported the most improvement in their condition . The new question naire provides a measure of outcome for TKR that is short , practical , reliable , valid and sensitive to clinical ly important changes over time BACKGROUND Little is known about the effects of total knee replacement surgery on the contributions of individual joint moments to the total support moment . A better underst and ing of these effects may enhance rehabilitation protocol s and determine factors related to long-term surgical outcome . METHOD Twenty-one subjects with total knee replacement and 21 controls performed level walking and stair ascent  at two testing periods , pre- and 6 months post-surgery . Variables studied included gait velocity , stride length , knee flexion angle , net joint moments of the hip , knee and ankle , and total support moment . Data were analyzed at the first peak vertical ground reaction force . FINDINGS For level walking , the total support moment , knee extensor moment , and knee flexion angle of total knee replacement patients were less than controls at post-surgery . For stair ascent , the patient group total support moment , ankle plantarflexor moment , and knee flexion angle were less than controls at both testing periods , while knee extensor moment was less than controls at post-surgery . Extensor synergies of the total knee replacement patients revealed less knee and more hip contributions during level walking and larger hip contributions during stair ascent to the total support moment than controls at both testing periods . INTERPRETATION A feature of total knee replacement gait , pre- and post-surgery , is a stiff knee attitude which may serve to protect the quadriceps . The larger hip extensor contribution to the total support moment observed in the patients may compensate for the diminished knee extensor contribution during level walking and stair ascent Objective To assess health-related quality of life ( HRQOL ) in a prospect i ve study with 7 years of follow-up in 49 consecutive patients who underwent a total joint replacement because of osteoarthritis . Methods Generic HRQOL was assessed with the  short-form 36 ( SF-36 ) and specific HRQOL with the Western Ontario and McMaster Universities Osteoarthritis Index ( WOMAC ) . Results Out of the 39 subjects who have completed the 7 years of follow-up of this study , 22 ( 56.4 % ) underwent a hip replacement surgery and the other 17 ( 43.6 % ) a knee replacement . Six months after surgery , a significant improvement , compared to preoperative scores , was observed in two of the eight dimensions of the SF-36 ( i.e. physical function and pain ) . The same dimensions , pain and physical function , at the same time , 6 months after surgery , measured by the WOMAC , showed a significant improvement as well , but there was no significant change in the stiffness score . From 6 months to the end of follow-up , changes in SF-36 scores showed a significant improvement in physical function ( p = 0.008 ) , role-physical ( p = 0.004 ) and role-emotional ( p = 0.01 ) while all scores of the WOMAC improved ( p < 0.001 for pain , p < 0.001 for stiffness and p < 0.01 for physical function ) . Conclusion The improvements observed in HRQOL at short term after surgery , are at least maintained over a 7-year follow-up period The role of the posterior cruciate ligament ( PCL ) remains controversial in total knee arthroplasty ( TKA ) , with some surgeons who believe in PCL sacrifice and substitution and others who believe in PCL preservation for stability . Manufacturers have developed both cruciate-substituting/posterior stabilized ( PS ) implants typically used when the ligament is sacrificed and cruciate retaining ( CR ) implants design ed for ligament preservation . However , studies demonstrate excellent clinical results with CR implants despite PCL sacrifice . This study sought to determine functional stability differences between PS and CR TKAs following PCL sacrifice . Eighteen ( 9 matched pairs ) subjects with either a PS or CR TKA and sacrificed PCL and a normal contralateral knee were subjected to physical exam and gait analysis ( walking , stair ascent and descent ) using a staircase model , passive reflective arrays and an optoelectric system . No differences were detected between the two groups among any of the measured parameters ( knee flexion angle , knee flexion moment , knee power absorption , pelvic tilt ) .  PCL sacrifice in a well-balanced cruciate retaining TKA did not result in instability during stair descent based on gait parameters . The decision to use a posterior stabilized design when faced with an incompetent PCL intraoperatively should be based on factors other than anticipated instability BACKGROUND Currently there is a limited underst and ing of the factors influencing range of motion by comparing patellar resurfacing vs non-resurfacing in total knee arthroplasty during activities of daily living . A recent meta- analysis of patellar replacement confirms better outcome with patella resurfacing ; however , the result can be influenced by many other factors , such as : component design , surgeon experience , and technical aspects of the surgery . This study compares the biomechanics of the knee in patients after total knee arthroplasty with and without patellar resurfacing during stair climbing . METHODS Forty-seven patients with total knee arthroplasty were assessed at the mean follow-up of 24 months . In all of them a posterior stabilised fixed bearing prosthesis ( Optetrak PS , Exactech ) was implanted . Twenty-six patients were treated without patellar resurfacing and 21 with patellar resurfacing . Clinical evaluations were performed using the International Knee Society and the Hospital for Special Surgery scores . Ten patients with patellar resurfacing and 10 patients without patellar resurfacing were also studied with motion analysis during stair climbing ; 10 healthy subjects were studied for statistical comparison . FINDINGS Clinical passive knee flexion , International Knee Society Function and Hospital for Special Surgery scores were significantly higher in the patellar resurfacing group . During stair climbing , active knee joint range of motion during the stance phase was greater in patients with patellar resurfacing . The maximum adduction moment was significantly higher in the group without patellar resurfacing . INTERPRETATION Patients with patellar resurfacing demonstrated better clinical scores , and kinematic and kinetic data while ascending stairs 
    Output:
    
During stair ascent , knee flexion angle at heel strike and walking velocity were reduced in  TKA subjects compared to controls .
Results of other variables were not consistent between studies .
Other results during stair descent were not consistent between studies .