title: Less Anterior Knee Pain with a Mobile-bearing Prosthesis Compared with a Fixed-bearing Prosthesis Mobile-bearing prosthesis did not improve mid-term clinical results of total knee arthroplasty Greater satisfaction in older patients with a mobile-bearing compared with fixed-bearing total knee arthroplasty. One Year After Navigated Total Knee Replacement, No Clinically Relevant Difference Found Between Fixed Bearing and Mobile Bearing Knee Replacement in a Double-Blind Randomized Controlled Trial Functional outcome of PFC Sigma fixed and rotating-platform total knee arthroplasty. A prospective randomised controlled trial Comparison of micromotion in mobile bearing and posterior stabilized total knee prostheses Functional performance of mobile versus fixed bearing total knee prostheses: a randomised controlled trial Comparison of mobile- and fixed-bearing cemented total knee arthroplasty. Questionnaire on the perceptions of patients about total knee replacement. Patient-reported outcomes after fixed- versus mobile-bearing total knee replacement: a multi-centre randomised controlled trial using the Kinemax total knee replacement. Clinical and radiological results of high flex total knee arthroplasty: a 5 year follow-up Mobile and fixed-bearing (all-polyethylene tibial component) total knee arthroplasty designs. A prospective randomized trial. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. Long-term comparison of mobile-bearing vs fixed-bearing total knee arthroplasty. Comparison of mobile-bearing and fixed-bearing total knee arthroplasty: a prospective randomized study. The Knee Arthroplasty Trial (KAT) design features, baseline characteristics, and two-year functional outcomes after alternative approaches to knee replacement. A comparison of fixed-bearing and mobile-bearing total knee arthroplasty at a minimum follow-up of 4.5 years. Mobile vs. fixed meniscal bearing in total knee replacement: a randomised radiostereometric study. The John Insall Award: No Functional Advantage of a Mobile Bearing Posterior Stabilized TKA Fixed versus rotating platform total knee arthroplasty: a prospective, randomized, single-blind study. Staged bilateral mobile-bearing and fixed-bearing total knee arthroplasty in the same patients: a prospective comparison of a posterior-stabilized prosthesis Relationship between joint gap difference and range of motion in total knee arthroplasty: a prospective randomised study between different platforms Fixed- versus Mobile-Bearing Total Knee Arthroplasty in Indian Patients Comparison of Fixed-Bearing and Mobile-Bearing Total Knee Arthroplasties Introduction of a new mobile-bearing total knee prosthesis: minimum three year follow-up of an RCT comparing it with a fixed-bearing device. Rotating Platform Knees Did Not Improve Patellar Tracking: A Prospective, Randomized Study of 240 Primary Total Knee Arthroplasties Early clinical results of a high-flexion, posterior-stabilized, mobile-bearing total knee arthroplasty: a US investigational device exemption trial. Mobile Bearings Do Not Improve Fixation in Cemented Total Knee Arthroplasty Loss of Tibial Bone Density in Patients with Rotating- or Fixed-platform TKA Real In Vivo Kinematic Differences between Mobile-Bearing and Fixed-Bearing Total Knee Arthroplasties Fixed-bearing versus mobile-bearing total knee arthroplasty: a prospective randomised, clinical and radiological study with mid-term results at 7 years. Fixed- vs mobile-bearing total knee arthroplasty: does it make a difference?--a prospective randomized study. Comparison of the tibiofemoral rotational alignment after mobile and fixed bearing total knee arthroplasty Randomized controlled trial of radiographic and patient-assessed outcomes following fixed versus rotating platform total knee arthroplasty.
abstract: Abstract  Anterior knee pain is one of the major short-term complaints after TKA . Since the introduction of the mobile-bearing TKA , numerous studies have attempted to confirm the theoretical advantages of a mobile-bearing TKA over a fixed-bearing TKA but most show little or no actual benefits . The concept of self-alignment for the mobile bearing suggests the posterior-stabilized mobile-bearing TKA would provide a lower incidence of anterior knee pain compared with a fixed-bearing TKA . We therefore asked whether the posterior-stabilized mobile-bearing knee would in fact reduce anterior knee pain . We r and omized 103 patients scheduled for cemented three-component TKA for osteoarthrosis in a prospect i ve , double-blind clinical trial . With a 1-year followup , more patients experienced persistent anterior knee pain in the posterior-stabilized fixed-bearing group ( 10 of 53 , 18.9 % ) than in the posterior-stabilized mobile-bearing group ( two of 47 , 4.3 % ) . No differences were observed for range of motion , visual analog scale for pain , Oxford 12-item question naire , SF-36 , or the American Knee Society score . The posterior-stabilized mobile-bearing knee therefore seems to provide a short-term advantage compared with the posterior-stabilized fixed-bearing knee . Level of Evidence : Level I , therapeutic study . See the Guidelines for Authors for a complete description of levels of evidence A prospect i ve study was performed to compare the clinical and radiological results of mobile- and fixed-bearing total knee arthroplasty  with specific attention to rotational alignment and range of motion . Sixty-one knees were assigned to total knee arthroplasty with either the NexGen LPS Flex fixed-bearing or with the NexGen LPS Flex mobile-bearing prosthesis . Postoperatively , knees were compared with regard to range of motion , clinical score , and radiographic findings . Rotational alignment of the femoral and tibial components was evaluated by computed tomography . The median follow-up period was 5.9 years ( range 2.1–8.8 years ) . Median postoperative Knee Society scores were 99 points ( 68–100 ) for the fixed-bearing group and 100 points ( 66–100 ) for the mobile-bearing group ( n.s . ) . The median postoperative flexion angles of 120 ° ( 90 ° –150 ° ) for the fixed-bearing group and 125 ° ( 90 ° –145 ° ) for the mobile-bearing group were not significantly different from each other ( n.s . ) . No knee required revision surgery due to wear of polyethylene or loosening of the component in either group . Computed tomography showed that 11 knees had rotational mismatches of more than 10 ° between the femoral and tibial components , but no significant difference was found in the postoperative extension and flexion angles or in the clinical score between the two treatment groups . Using the identical design for both fixed- and mobile-bearing prostheses , this prospect i ve , r and omized study did not show any clinical advantages of the mobile-bearing knee . Analysis of rotational alignment by CT scan did not reveal a particular advantage of the self-aligning mechanism of mobile-bearing implants A prospect i ve , r and omized , controlled , double-blind trial was performed to compare outcomes between 61 mobile- and 58 fixed-bearing primary TKAs in patients aged 70 years or older . At last follow-up , no difference was found for Knee Society score . The mobile-bearing group had greater knee flexion at 3 and 6 months , but this was similar at 2 years . The patient satisfaction was better in the mobile-bearing group than in fixed-bearing group , with respect to Knee Society functional score , Western Ontario MacMasters University score , Short-Form 12 score , and visual analog scale score . A multivariate analysis confirmed that the only independent factors predictive of postoperative quality of life were early postoperative flexion . We believe that better perception and satisfaction with mobile-bearing in older patients was due to the earlier regain of their knee flexion . Our results justify the use of mobile-bearing design in the older population Background : The mobile bearing design s have not yet been shown to improve clinical outcome of total knee arthroplasty ( TKA ) . In this prospect i ve r and omized study , we compared the short-term clinical results of a mobile bearing implant with those of the fixed bearing version of the same implant . Methods : We r and omized 100 knees into two double-blind groups who received either the fixed ( FB , 52 knees ) or the mobile bearing ( MB , 48 knees ) version of the same implant .  We used navigation to st and ardize the surgical technique . For up to one year , we recorded the Knee Society ( KSS ) and Oxford ( OXF ) scores . We performed an exploratory analysis of variance ( ANOVA ) to determine the influence of baseline scores as covariate and the extent of improvement in clinical outcome over time . Results : After one year , we did not detect any statistically significant difference between the two groups . The KSS scores differed by 2 points , the OXF scores by 1.1 points . Conclusion : Even with identical geometry of implant surfaces and a navigated surgical technique , first-year results do not support a preference for either a fixed or a mobile design The aim of this study was to determine whether there is a difference in functional outcome between the PFC Sigma fixed-bearing and rotating-platform total knee replacement systems .  One hundred twenty patients were r and omised to receive either a fixed-bearing or rotating-platform PFC Sigma total knee replacement .  Range of movement ( ROM ) , Oxford knee score ( OKS ) and Knee Society score ( KSS ) were assessed independently before and one year after surgery . Weight-bearing X-rays were taken immediately and one year post surgery to determine the incidence of osteolysis and loosening . At a mean follow-up of 13.4 months there was no statistically significant difference in mean ROM , OKS and KSS between the two groups . There was no evidence of osteolysis or loosening in either of the groups and no revision for infection or implant failure . This study shows that there is no statistically significant difference in functional outcome between the two types of implants at short-term follow-up Background On theoretical grounds mobile bearing total knees should reduce the micromotion of the tibial component relative to the bone . Patients and methods We used radiostereometric analysis to measure the three-dimensional micromotion in  42 tibial components  during 2 years of follow-up . The patients had been r and omized as to whether they would receive a mobile bearing ( MB ) or posterior stabilized ( PS ) design .  We expected that the MB knee would facilitate dissipation of forces from the prosthesis-bone interface by the motion of the bearing and by load sharing with the soft tissues , leading to less micromotion . In the PS design s , limited free rotation caused by the campost articulation might cause additional stress at the bone-prosthesis interface . Results We found no significant differences between the MB and PS group at the 2-year follow-up evaluation with respect to Knee Society scores and radiographic results . The PS group had a higher variability in subsidence and anterior-posterior tilting of the component than the MB group . Interpretation The low variability of the data in the MB knee prosthesis group suggests that this design is more predictable and forgiving with respect to micromotion of the tibial component Purpose The primary goal of this study was to assess the difference in active flexion between patients with a mobile versus a fixed bearing , cruciate retaining , and total knee arthroplasty .  The study was design ed as a r and omised controlled multi-centre trial . Methods Participants were assigned to interventions by using block-stratified , r and om allocation . Outcome parameters were active flexion , passive flexion , and Knee Society Score ( KSS ) . Outcome parameters were assessed preoperatively and at 3 , 6 , and 12 months postoperatively by an independent nurse . Results Ninety-two patients from one centre were included , 46 in each group . Active flexion was comparable for the two groups , 99.9 ° for the mobile bearing group and 101 ° for the fixed bearing group with a baseline controlled difference of 1.0 ( 95 % CI −3.9 to 5.8 , n.s . ) . The Clinical KSS was comparable between the two bearing groups ( Mobile 90.0 vs. fixed 92.4 , n.s . ) . The functional KSS showed a difference that was attributable to the stair climbing subscore , which showed a difference in favour of the fixed bearing design between preoperative and 3 months ( 7.3 point difference ; 95 % CI 2.3–12.5 ; P = 0.005 ) as well as 12 months ( 4.8 point difference ; 95 % CI 0.1–9.6 ; P = 0.045 ) . Conclusions There were no short-term differences in active flexion  between fixed bearing and mobile bearing total knee arthroplasty . Level of evidence Concern about polyethylene wear and related osteolysis after knee arthroplasty has developed in the last years . Mobile-bearing knee prostheses were design ed in order to reduce the influence of this critical factor on long-term success of total knee replacement . We present a prospect i ve study comparing clinical and radiological results with a mobile-bearing ( Ceragyr ) and a fixed-bearing knee prosthesis ( posterior stabilized Hermes ) . Clinical results did not show any significant differences in Knee Society scores . We found better results in the mobile-bearing group for pain scores and subjective preference , but the difference did not reach statistical significance . Within the time limits of this study , radiological analysis showed no osteolysis in either group , but longer follow-up will be needed to confirm this 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 We compared patient-reported outcomes of the Kinemax fixed- and mobile-bearing total knee replacement in a multi-centre r and omised controlled trial . Patients were  r and omised to the fixed- or the mobile-bearing prosthesis via a sealed envelope method after the bone cuts had been made in the operating theatre . R and omisation was stratified by centre and diagnosis . Patients were assessed pre-operatively and at eight to 12 weeks , one year and two years post-operatively . Vali date d question naires were used which included the Western Ontario MacMasters University , Short-Form 12 , Mental Health Index-5 , Knee Injury and Osteoarthritis Outcome Score for Knee-Related Quality of Life and Function in Sport and Recreation scales and a vali date d scale of satisfaction post-operatively . In total , 242 patients ( 250 knees ) with a mean age of 68 years ( 40 to 80 ) were recruited from four NHS orthopaedic centres . Of these , 132 patients ( 54.5 % ) were women . No statistically significant differences could be identified in any of the patient-reported outcome scores between patients who received the fixed-bearing or the mobile-bearing knee up to two-years post-operatively Introduction In a prospect i ve r and omized study , we compared the results after implantation of the mobile bearing high flex TKA with a fixed bearing posterior stabilized TKA in 60 patients ( 30 patients each group ) . Method We evaluated the hospital for special surgery-score ( HSS ) and different radiological parameters preoperatively , as well as 3 months , 3 and 5 years postoperatively . Result Three months postoperatively , the high flex group showed better results in scores for pain , ROM ( 122.5 ° vs. 107.33 ° ) , as well as in the overall HSS ( 87.21 vs. 82.68 points ) . Three and 5 years postoperatively , there were no differences between both the groups in all scores , but the HSS is still increasing . Conclusion The theoretical advantages of the mobile bearing knee prostheses were reflected in the clinical results , only partly and temporarily BACKGROUND Proponents of mobile-bearing total knee arthroplasty believe that it has potential advantages over a fixed-bearing design in terms of diminished wear and improved motion and /or function , but these advantages have not been demonstrated in a r and omized clinical comparison to our knowledge . We conducted a patient-blinded , prospect i ve , r and omized clinical trial to compare mobile-bearing and fixed-bearing cruciate-substituting total knee arthroplasties of the same design . METHODS Patients between the ages of sixty and eighty-five years were prospect ively r and omized to receive a cruciate-substituting rotating-platform design or a fixed-bearing design with an all-polyethylene tibial component . There were no significant differences in the demographic characteristics ( mean age , 72.2 years ; mean American Society of Anesthesiologists score , 2.7 ; mean body mass index , 31.8 kg/m(2 ) ) or preoperative clinical or radiographic measures between the groups . Routine clinical and radiographic follow-up measures included the Knee Society score ( KSS ) , Western Ontario and McMaster Universities Osteoarthritis Index ( WOMAC ) , and Short Form-36 ( SF-36 ) outcome measures . RESULTS The results of 312 arthroplasties ( 136 with an all-polyethylene tibial component  and 176 rotating-platform design s ) in 273 patients were analyzed at a minimum of two years ( mean , forty-two months ) postoperatively . Although there was significant improvement in both groups , there was no significant difference between the groups with regard to the mean postoperative range of motion ( 110.9 degrees and 109.1 degrees , respectively ; p = 0.21 ) , the mean KSS clinical score ( 90.4 and 88.2 points ; p = 0.168 ) , or the mean KSS pain score ( 44.9 and 43.1 points ; p = 0.108 ) at this follow-up point . There were ten revisions : seven because of infection , one because of patellar fracture , one because of instability , and one because of aseptic loosening . CONCLUSIONS The two design s functioned equivalently at the time of early follow-up in this low-to-moderate-dem and patient group . The rotating-platform design had no significant clinical advantage over the design with the all-polyethylene tibial component Within the context of a double blind r and omized controlled parallel trial of 2 nonsteroidal antiinflammatory drugs , we vali date d WOMAC , a new multidimensional , self-administered health status instrument for patients with osteoarthritis of the hip or knee . The pain , stiffness and physical function subscales fulfil conventional criteria for face , content and construct validity , reliability , responsiveness and relative efficiency . WOMAC is a disease-specific purpose built high performance instrument for evaluative research in osteoarthritis clinical trials Few published reports have been published regarding a comparison of the long-term outcomes between mobile- ( MB ) and fixed-bearing component design s for knee arthroplasty . The minimum 10-year clinical and radiologic follow-up of an unselected consecutive series of 89 patients ( 107 knees ) who were r and omized to have one of these different design s for primary arthroplasty was done . Twenty-six patients ( 30 knees ) who had a fixed-bearing design and 24 patients ( 33 knees ) who had an MB prosthesis were available for follow-up . Two MB knees were revised for aseptic loosening of a tibial component in one and femoral component fracture in the other . In patients who did not have revision surgery , there were no differences between the groups with respect to mean Knee Society scores , knee flexion , or pain scores The purpose of this prospect i ve r and omized study was to compare the postoperative recovery and early results of 2 groups of patients undergoing total knee arthroplasty : 107 patients received an established fixed-bearing posterior-stabilized prosthesis ( Legacy Posterior Stabilized [ LPS ] ) , and 103 patients the meniscal-bearing prosthesis ( Meniscal Bearing Knee [ MBK ] ) .  Surgical procedures were the same for both groups except for posterior cruciate ligament management , which was sacrificed in the LPS group and spared but completely released from the tibia in the MBK group . At an average follow-up of 36 months , knee , function , and patellar scores were comparable in both groups . The LPS group showed a significantly higher maximum flexion than the MBK group ( 112 degrees vs 108 degrees ) . Using a fixed-bearing or a mobile-bearing design did not seem to influence the short-term recovery and early results after knee arthroplasty . Key words : total knee arthroplasty , mobile bearing , knee prosthesis , meniscal-bearing knee , posterior stabilized , prospect i ve r and omized BACKGROUND The aim of continued development of total knee replacement systems has been the further improvement of the quality of life and increasing the duration of prosthetic survival . Our goal was to evaluate the effects of several design features , including metal backing of the tibial component , patellar resurfacing , and a mobile bearing between the tibial and femoral components , on the function and survival of the implant . METHODS A pragmatic , multicenter , r and omized , controlled trial involving 116 surgeons in thirty-four centers in the United Kingdom was performed ; 2352 participants were r and omly allocated to be treated  with or without a metal backing of the tibial component ( 409 ) , with or without patellar resurfacing ( 1715 ) , and /or with or without a mobile bearing ( 539 ) . R and omization to more than one comparison was allowed . The primary outcome measures were the Oxford Knee Score ( OKS ) , Short Form-12 , EuroQol-5D , and the need for additional surgery . The results up to two years postoperatively are reported . RESULTS Functional status and quality -of-life scores were low at baseline but improved markedly across all trial groups following knee replacement ( mean overall OKS , 17.98 points at baseline and 34.82 points at two years ) . Most of the change was observed at three months after the surgery . Six percent of the patients had additional knee surgery within two years . There was no evidence of differences in clinical , functional , or quality -of-life measures between the r and omized groups at two years . CONCLUSIONS Patients have substantial improvement following total knee replacement . This is the first adequately powered r and omized controlled trial , of which we are aware , in which the effects of metal backing , patellar resurfacing , and a mobile bearing were investigated . We found no evidence of an effect of these variants on the rate of early complications or on functional recovery up to two years after total knee replacement BACKGROUND Durable long-term independent results with the Low Contact Stress rotating-platform ( mobile-bearing ) and the Insall Burstein-II ( fixed-bearing ) total knee prostheses have been reported , but no studies describing either the mid-term or long-term results and comparing the two prostheses are available , to our knowledge . METHODS Thirty-two patients who had bilateral arthritis of the knee with similar deformity and preoperative range of motion on both sides and who agreed to have one knee replaced with a mobile-bearing total knee design and the other with a fixed-bearing design were prospect ively evaluated . Comparative analysis of both design s was done at a mean follow-up period of six years , minimizing patient , surgeon , and observer-related bias . Clinical and radiographic outcome , survival , and complication rates were compared . RESULTS Patients with osteoarthritis had better function scores and range of motion compared with patients with rheumatoid arthritis . However , with the numbers available , no benefit of mobile-bearing over fixed-bearing design s could be demonstrated with respect to Knee Society scores , range of flexion , subject preference , or patellofemoral complication rates . Radiographs showed no difference in prosthetic alignment . Two knees with a mobile-bearing prosthesis required a reoperation : one had an early revision because of bearing dislocation and another required conversion to an arthrodesis to treat a deep infection . CONCLUSIONS We found no advantage of the mobile-bearing arthroplasty over the fixed-bearing arthroplasty with regard to the clinical results at mid-term follow-up . The risk of bearing subluxation and dislocation in knees with the mobile-bearing prosthesis is a cause for concern and may necessitate early revision . LEVEL OF EVIDENCE Therapeutic Level II 52 knees scheduled for a total knee arthroplasty were r and omised to either a fixed or a mobile polyethylene bearing . The design was identical in all parts . The knee systems used were the Rotaglide Total Knee System ( RTK ) and the Nuffield Total Knee System ( NTK ) , both from the same manufacturer ( Corin Medical Ltd. , UK ) . All knees implanted were uncemented . The patients were followed for 2 years clinical ly and with radiostereometric analyses to assess migration over time and inducible displacement of the tibial component . Separate analysis of the mobility of the tibial insert in the knees with a mobile bearing was also made . The migration measured with RSA between the 1st and 2nd year expressed as maximum total point motion ( MTPM ) might predict the risk of loosening of the implant . There were no differences between the groups regarding clinical outcome ( HSS Knee score ) , migration or inducible displacement during the 2 years follow-up . The movement between the tibial tray and the mobile meniscal insert expressed as maximum total point motion ( MTPM ) was 6.8+/-3.3 mm at the 1st year follow-up Background Mobile bearing ( MB ) total knee design has been advocated as a means to enhance the functional characteristics and decrease the wear rates of condylar total knee arthroplasty ( TKA ) . However , it is unclear if these design s achieve these goals . Questions / purpose sWe asked whether function of patients or survivorship would be greater or complications would be lesser in groups of patients with MB compared with fixed bearing ( FB ) TKA .  We also sought to describe retrieval findings . Methods We r and omized 507 primary TKAs in 416 eligible patients to receive MB ( n = 252 ) or FB ( n = 255 ) devices from November 2001 to August 2007 ( Investigational Device Exemption G000180 , Clinical Trials.gov registration number NCT00946075 ) . Patients were blinded to treatment allocation . WOMAC Index , SF-12 Health Survey , knee range of motion , and Knee Society scores were collected and compared preoperatively and at 6 , 12 , and 24 months postoperatively . We recorded device failures and complications until October 2009 . Kaplan-Meier survivorship was compared using the log rank test . Twelve retrieved MB devices underwent pathologic analysis . The minimum postoperative time was 2.2 years ( mean , 5.9 years ; range , 2.2–7.9 years ) . Results We found no differences in mean clinical assessment scores or mean score changes from baseline at any postoperative interval through 2 postoperative years . Nineteen of the 252 MB and 13 of the 255 FB knees had undergone revision of any component . Estimated survival at 6 postoperative years was similar for the two devices : 90.1 % ( 95 % confidence interval [ CI ] , 84.1–93.9 ) for MB and 94.2 % ( 95 % CI , 90.1–96.6 ) for FB . Two MB and no FB tibial components were revised for loosening . There was one case of MB insert dislocation . Retrieved MB devices demonstrated no unexpected wear or mechanical device failures . Conclusion We found no evidence of functional advantage of the MB design . Survivorship was similar , although the study is limited by short duration of followup . Level of Evidence Level I , therapeutic study . See Guidelines for Authors for a complete description of levels of evidence The purpose of this r and omized , single-blind clinical trial was to compare a rotating platform ( RP ) total knee arthroplasty to a fixed-bearing ( FB ) total knee arthroplasty . Ninety-five knees in 69 patients were implanted by 2 surgeons . There were no significant differences in the preoperative demographics . At a minimum of 2-year follow-up , clinical outcomes and complication rates were similar , with the exception that the RP group had significantly better stair-climbing scores ( P = .04 ) . Postoperative range of motion was equally good in both groups ( FB knees , 1 ° -125 ° ; RP knees , 1 - 126 ° ) . There were no bearing dislocations in the RP group . In conclusion , this RP design performs at least as well as the FB version , and the RP patients reported better stair-climbing ability . Enthusiasm for this finding should be tempered by the relatively small sample size Mobile-bearing total knee arthroplasty ( TKA ) has several theoretical advantages over fixed-bearing TKA . We conducted a prospect i ve r and omized trial to compare the results of mobile-bearing and fixed-bearing posterior-stabilized TKA in the same patients using the same femoral component design of a mobile-bearing prosthesis in one knee and a fixed-bearing prosthesis in the other knee in 25 patients with osteoarthritis . The mean follow-up was 40 months . No significant differences were found in the mobile-bearing and fixed-bearing knees in terms of clinical and radiographic results . No osteolysis , loosening , or revision occurred . One knee with a mobile-bearing prosthesis had a dislocation of the rotating bearing ; however , spontaneous reduction occurred and the dislocation did not recur . Satisfactory early results can be achieved in both mobile-bearing and fixed-bearing knees . We could not demonstrate an advantage of a mobile-bearing TKA The objective of this study was to investigate the range of motion ( ROM ) of the knee before and four years after total knee arthroplasty ( TKA ) with a mobile or fixed type of platform and to prospect ively evaluate whether there was a difference in ligament balance between the platform types . The subjects were 68 patients involving 76 joints . The mobile type was used in 31 joints and fixed type in 45 joints by employing a prospect i ve r and omised method . The passive maximum ROM was measured using a goniometer before and four years after surgery . Also , the intraoperative knee ligament balance was measured . The postoperative extension ROM was significantly improved after TKA using a mobile bearing type compared with that employing a fixed bearing type . In TKA using the former , the intraoperative gap difference was not related to the postoperative flexion angle of the knee . However , they were related in TKA using a fixed bearing type , with a positive correlation regarding the flexion gap Purpose . To compare the mid-term clinical outcomes in Indian patients after total knee arthroplasty ( TKA ) using a fixed- or mobile-bearing prosthesis . Methods . 120 consecutive patients ( 50 men and 70 women ) aged 55 to 76 ( mean , 63 ) years who had arthritis of the knee with similar deformity and range of motion were r and omised to undergo TKA using a fixed- or mobile-bearing prosthesis .  Patients with mediolateral instability and infective arthritis were excluded .  Knee Society knee and functional scores , range of motion , and the presence of flexion contracture were assessed . Results . The mean follow-up duration was 3.5 ( range , 1–4.6 ) years . The mid-term outcome of the 2 groups was comparable . One patient with a mobile-bearing prosthesis had recurrent dislocation at postoperative week 2 , owing to iatrogenic medial collateral ligament injury . Conclusion . Long-term studies of both functional and radiological outcomes are needed to determine the indications for fixed- versus mobile-bearing prostheses The purpose of the current study was to directly compare the results of fixed-bearing and mobile-bearing total knee arthroplasties in the same patient who had bilateral simultaneous total knee replacements . A fixed-bearing total knee prosthesis ( AMK ) was implanted in one knee and a mobile-bearing total knee prosthesis ( LCS ) was implanted in the other knee in 116 patients . The average age of the patients was 65 years ( range , 33–70 years ) . The average followup was 7.4 years ( range , 6–8 years ) .  Clinical and radiographic followup was done using Knee Society and Hospital for Special Surgery knee rating systems at 6 weeks , 3 months , 6 months , 1 year after surgery , and yearly thereafter . Total knee score , pain score , mean functional score , and range of motion were comparable in both groups . Two knee replacements ( 2 % ) in one patient with AMK prostheses were revised because of complete wear of tibial bearing polyethylene . One knee replacement ( 1 % ) in one patient with an LCS prosthesis was revised because of dislocation of the medial tibial bearing polyethylene and one knee replacement ( 1 % ) in one patient with an LCS prosthesis was revised because of complete wear of the medial tibial bearing polyethylene . No knee had aseptic loosening or osteolysis in either group . After a minimum followup of 6 years , the results of fixed- and mobile-bearing total knee prostheses in the current series are favorable . However , there is no evidence to prove the superiority of the mobile-bearing total knee design As part of the step-wise validation of a new prosthesis ( TMK ) , we previously published the 1 year results of a r and omised controlled trial in patients undergoing bilateral knee replacement  [ Price A. , Rees J. , Beard D. , Juszczak E. et al. A mobile-bearing total knee prosthesis compared with a fixed-bearing prosthesis . JBJS B 2003;85-B-1:62 - 7 . ] . Forty patients had the new mobile-bearing prosthesis implanted in one knee and an established fixed-bearing device in the other ( AGC ) . We now report the 3 year status of these patients and , in addition , review a separate multi-centre cohort of 172 patients who had undergone unilateral arthroplasty with the TMK .  No significant differences were found in outcome ( American Knee Society Score and Oxford Knee Score ) between the two prostheses . The greater incidence of " clicking " in the mobile-bearing knee , reported in the previous review , persisted ( TMK=48 % , AGC=30 % ) . The presence of this mechanical noise was found to have no relationship with outcome in either of the prostheses . The unilateral cohort study showed an acceptable complication rate for the new prosthesis , although some patients reported subjective instability . The method of controlled introduction of the TMK , of which this constitutes a further step , has allowed us to assess the significance of a reported problem ( clicking ) and to provide scientific data from which other surgeons can decide about use of the implant Renewed interest in mobile-bearing total knee replacement design s has been generated by the concept of self alignment and the suggestion that those design s can accommo date small mismatches in the rotational position of the tibial and femoral components . Self alignment might improve patellar tracking , decrease the prevalence of lateral retinacular release and postoperative patellar tilt or subluxation , improve knee flexion , and improve patellofemoral function during daily activities such as stair climbing . This prospect i ve r and omized study of 240 patients used a single posterior-stabilized femoral component  and included three groups of 80 patients : an  all-polyethylene group , a modular metal-backed group , and a rotating platform tibia group . The prevalence of lateral retinacular release was 3.8 % in each group . The prevalence of patellar tilt was 5 % ( all-polyethylene group ) , 7 % ( modular metal-backed group ) , and 11 % ( rotating platform group ) . Preoperative motion was not significantly different and both the 3-month flexion ( 112 ° , 110 ° , and 108 ° ) and 1-year flexion ( 116 ° , 117 ° , and 115 ° ) were not significantly different among the all-polyethylene , modular metal-backed , and rotating platform groups , respectively . Preoperative stair climbing scores were not significantly different and both the 3-month ( 38 , 41 , and 35 points ) and 1-year ( 44 , 46 , and 42 points ) scores were not significantly different . In this prospect i ve r and omized study , the rotating platform knee design did not decrease the prevalence of lateral retinacular release or patellar tilt or subluxation and did not increase knee flexion or improve stair climbing ability at 3 months or at 1 year postoperatively when compared with a posterior-stabilized , fixed-bearing knee Between May 2001 and June 2004 , 388 total knee arthroplasty cases were enrolled in a prospect i ve , r and omized , multicenter investigational device exemption trial . Patients received either the investigational high-flexion mobile-bearing knee or a fixed-bearing control . At 2 to 4 years of follow-up , results in 293 patients with degenerative joint disease were compared using Knee Society Assessment and Function scores , radiographic results , complications analysis , and survival estimates . The mobile-bearing and fixed-bearing groups demonstrated similar , significant improvement over preoperative assessment s in Knee Scores , maximum flexion , and range of motion . One mobile-bearing arthroplasty required revision . Radiographic results were unremarkable , and implant-related complications were rare in both groups . At this early follow-up , the investigational high-flexion mobile-bearing knee and its fixed-bearing counterpart demonstrated comparable , effective performance Mobile bearings were introduced to improve wear and knee kinematics . By uncoupling the forces generated at the articulation from the implant-bone interface this would , theoretically , also improve the fixation of the implant to bone . We did this study to evaluate whether mobile bearings  improve the fixation of the tibial component to bone .  Fifty-two consecutive knees in 47 patients ( average age , 72 years ; range , 62 - 84 years ) with primary osteoarthrosis were r and omized into two groups to receive a cemented total knee arthroplasty with either a fixed-bearing or mobile-bearing tibial component . The quality of fixation was analyzed with radiostereometric analysis for up to 2 years . Mobile bearings did not improve fixation . Both magnitudes and directions of component rotations were similar , and the number of implants with continuous migration was almost identical . Both implant types had a combination of subsidence and lift-off , but where the mobile bearing implants displayed more of subsidence , the fixed bearing knees showed more lift-off . It might be that the somewhat stiffer cobalt-chromium baseplate or the different joint conformity used in the mobile-bearing knees counteracts any potential effects of the mobile bearing . Level of Evidence : Therapeutic Level I. See the Guidelines for Authors for a complete description of levels of evidence Little is known about tibial bone remodeling with TKA and its clinical relevance . We performed a r and omized clinical trial to compare tibial bone density changes in cemented components with different bearing design s. Bone density changes were assessed using quantitative computed tomography (qCT)-assisted osteodensitometry . Twenty-eight rotating-platform and 26 fixed-platform cemented TKAs were included . The nonoperated contralateral side was used as a control . CT scans were performed postoperatively and 1 year and 2 years after the index operation . Cancellous bone density loss ( up to 12.6 % at 2 years ) was observed in all proximal tibial regions in both cohorts . In contrast , we found lower cortical bone density loss ( up to 3.6 % at 2 years ) . We found no differences in bone loss between fixed- and rotating-platform implants . The decrease of cancellous bone density after TKA suggests stress transfer to the cortical bone We did an in vivo fluoroscopic study comparing the sagittal plane kinematics of mobile-bearing and fixed-bearing total knee arthroplasties in a unique group of patients . These patients were part of a larger bilateral r and omized controlled outcome trial with each patient having received both types of total knee arthroplasties . Invited patients did three exercises with each of their different knee replacements ; extension against gravity , flexion against gravity , and a step-up . These exercises were recorded using video fluoroscopy , and a series of still digital images over the flexion range were retrieved . The relationship of patella tendon angle to knee flexion angle for each patient was derived . The patella tendon angle to knee flexion angle of the mobile-bearing knee behaved in a linear manner more closely replicating the normal knee , whereas the fixed-bearing knee behaved in a nonlinear , more variable manner . This pattern of results was similar for all three exercises with each patient having one knee replacement that behaved differently in the sagittal plane when compared with their other knee replacement . These kinematic differences may explain the clinical differences observed in the r and omized controlled trials that compared these two total knee arthroplasties Mobile-bearing ( MB ) total knee arthroplasty ( TKA ) was developed as an alternative to the established fixed-bearing ( FB ) design because of theoretical advantages . Short-term studies comparing these design s have not shown any differences in clinical and radiographic results . We compared the results at 7 years of a r and omised study of patients undergoing TKA using either a FB or a MB variant of the same prosthesis . Fifty-two patients ( 52 knees ) with an average age of 70 years received a FB posterior-stabilized prosthesis , and 50 patients ( 52 knees ) with an average age of 72 years , a MB prosthesis .  All implants were cemented and the patella was routinely resurfaced . Preoperatively , there were no differences between the two groups , and surgical procedure and postoperative protocol were the same for both . At an average follow-up of 7.1 years , no significant differences of FB over MB design could be demonstrated with respect to the American Knee Society score ( AKSS ) , pain score , a question naire of general health ( SF-12 score ) , range of motion ( ROM ) , or complication rates . Radiographs showed no significant difference in prosthetic alignment or evidence of loosening . Two knees with a MB design required reoperation , one for persistent joint stiffness and another to treat septic loosening . One patient with a MB prosthesis with signs of tibial component loosening was asymptomatic . We conclude that at mid-term follow-up there is no evidence to prove the superiority of MB over FB TKA with regard to the clinical and radiographic results The purpose of this prospect i ve , r and omized study was to compare the early clinical and functional results of primary total knee arthroplasty using a fixed-bearing ( FB ) and a rotating-platform ( RP ) prosthesis .  Outcomes including range of motion ( ROM ) , Knee Society Score , Western Ontario MacMaster ( WOMAC ) , and Short Form-36 ( SF-36 ) were measured preoperatively and at 6 weeks , 3 months , 6 months , 1 year , and 2 years . Radiographic analysis was performed . There were 72 FB and 68 RP knees . The RP group had a greater ROM at 6 weeks and 1 year . This difference was not statistically significant at 2 years . There were no differences in the ROM at any other period . There were no significant differences in Knee Society Score , Short Form-36 , or Western Ontario MacMaster scores at any period . No clinical ly significant differences were noted in the radiographic analysis . The use of a FB or RP design did not affect the early functional outcomes after total knee arthroplasty Purpose The anatomical l and mark for the anteroposterior ( AP ) axis of the proximal tibia and its variability was investigated in order to determine whether a certain l and mark could be employed as a reference axis for the proximal tibia after the rotating platform mobile bearing and fixed bearing total knee arthroplasties ( TKAs ) . Methods Eighty primary osteoarthritic knees were r and omized to undergo either rotating platform mobile bearing ( Group A , n = 40 ) or fixed bearing ( Group B , n = 40 ) TKAs , and were followed up for 31 and 30 months , respectively . The AP axes were defined for the distal femur , proximal tibia , ankle , and each TKA component on the reconstructed CT scan and the angles between the distal femoral AP axis and those of each bone or component were estimated . Clinical and radiographic outcomes were evaluated during the follow up . Results A significant difference was seen between the preoperative and postoperative rotational position of the proximal tibia relative to the distal femur following rotating platform mobile bearing TKA ( P = 0.014 ) whereas no such difference was seen after fixed bearing TKA .  The mean postoperative alignment of the tibia differed between the two groups ( Group A : Group B = −2.9:0.2 , P = 0.010 ) and its variability was significantly greater in group A ( P < 0.001 ) . There were no differences in the clinical outcomes including range of motion , knee society score , function score , HSS , and WOMAC score as well as the mean postoperative coronal tibiofemoral alignment between the two groups . Conclusion The unpredictable change in the rotational axis of the tibia and its broad variability after rotating platform mobile bearing TKA may provide a warning against the use of a fixed l and mark for establishing tibial rotational alignment . Level of evidence Prospect i ve comparative study , Level II This prospect ively blinded r and omized controlled study evaluated the difference in the functional and radiological outcomes in patients who received a press-fit condylar Sigma cemented cruciate-substituting total knee arthroplasty with either a rotating platform ( RP ) or a fixed bearing ( FB ) .  There were 51 joints in 49 patients : 24 joints in the RP group ( mean follow-up , 43 months ) and 27 joints in the FB group ( mean follow-up , 40 months ) . At baseline , there was no significant difference in age , body mass index , preoperative diagnosis , Charnley class , range of motion , clinical and functional scores , between the RP and FB groups . At mid-term follow up both the RP and FB give equivalent results , but patients with the RP tended to have a higher activity level score
target: Meta-analyses showed no clinical ly relevant differences in terms of revision rates , clinical outcome scores or patient-reported outcome measures between MB and FB TKRs .
  It appears that theoretical assumptions of superiority of MB over FB TKR are not borne out in clinical practice
background: Mobile-bearing ( MB ) total knee replacement ( TKR ) was introduced to reduce the risk of aseptic loosening and wear of polyethylene inserts .
  However , no consistent clinical advantages of mobile- over fixed-bearing ( FB ) TKR have been found .
  In this study we evaluated whether mobile bearings have an advantage over fixed bearings with regard to revision rates and clinical outcome scores .
  Furthermore , we determined which modifying variables affected the outcome .