***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: Introduction Previous radiostereometric studies have revealed abnormal anterior-posterior translation of the femur in patients operated with AMK ( DePuy , Johnson and Johnson , Leeds , UK ) total knee arthroplasty ( TKA ) . Based on these observations , we hypothesized that patients with TKA have an abnormal gait pattern , and that there are differences in kinematics depending on the design of the tibial joint area . Method We used a gait analysis system to evaluate the influence of joint area design on the kinematics of the hip and knee during level walking .  39 TKA patients ( 42 knees ) and 18 healthy age-matched controls were studied . Patients with 5 ° varus/valgus alignment or less were r and omized to receive either a relatively flat or a concave tibial insert with retention of the posterior cruciate ligament .  Patients who had more than 5 ° varus-valgus alignment and /or extension defect of 10 ° or more were r and omized to receive the concave or a posterior-stabilized tibial component with resection of the posterior cruciate ligament . Results Patients with TKA tended to have less hip and knee extension and decreased knee and hip extension moment than controls . They also tended to walk more slowly . TKA altered the gait pattern , but choice of implant design had little influence . Interpretation In patients with a similar degree of degenerative joint disease and within the limits of the constraints offered by the prostheses under study , the choice of joint area constraint has little influence on the gait pattern OBJECTIVE The aim of this study is to evaluate residual muscle function abnormalities after total knee replacement  , with respect to gait kinematics and kinetics . DESIGN Longitudinal study on a follow-up of up to two years . BACKGROUND Gait usually presents an excellent improvement after total knee replacement . Nevertheless , some kinematics and kinetics abnormalities persist even after a long period of time and they might have implication s in long-term prosthesis failure . Additionally , lower limb muscle activity has not been sufficiently studied in the past directly by means of dynamic EMG . METHODS Nine patients who had a posterior cruciate sparing total knee replacement design  were evaluated by means of clinical assessment and gait analysis at the end of rehabilitation trials at six , twelve and twenty four months .  EMG from trunk and lower limb muscles was registered and elaborated through a statistical detector for the on-off timing . RESULTS Gait analysis showed a slow gait , with a " stiff knee gait pattern " and prolonged muscular co-contractions during stance . CONCLUSIONS Knee kinematics and kinetics abnormalities during loading acceptance after total knee replacement are associated with co-contractions in muscular activation pattern . RELEVANCE Gait pattern at two years after total knee replacement is deemed unphysiological , potentially dangerous for the implant duration in time and responsible for residual disability in patients . Muscular behavior during daily activities provides insight into the integration of the prosthetic biomechanics within the muscular-skeletal system . This information is of relevance to improve prosthetic design , rehabilitation programs and knee motor performance OBJECTIVE Patients with unilateral hip or knee replacements for end-stage osteoarthritis ( OA ) are at high risk for future progression of OA in other joints of the lower extremities , often requiring additional joint replacements . Although the risks of future surgery in the contralateral cognate joints ( i.e. , contralateral hip replacement after an initial hip replacement ) have been evaluated , the evolution of end-stage hip OA to OA involving the knee joints , and vice versa ( i.e. , noncognate progression ) has not been investigated . Because characterization of OA progression in noncognate joints may shed light on the pathogenesis of multijoint OA , we investigated the pattern of evolution of end-stage lower extremity OA in a large , clinical cohort . METHODS Total joint replacement ( TJR ) was selected as a marker of end-stage OA , and a data base comprising all lower extremity TJRs performed at a large referral center between 1981 and 2001 was accessed . Of the 5,894 patients identified , 486 patients with idiopathic OA who underwent hip replacement and 414 who underwent initial knee replacement  were analyzed to determine the relative likelihood of subsequent TJRs .  Patients with the systemic inflammatory arthropathy , rheumatoid arthritis ( RA ) , were evaluated as a control population because RA progression is not considered to be a primarily mechanically mediated process . RESULTS The contralateral cognate joint was the most common second joint to undergo replacement in both the OA and the RA groups . However , in OA patients for whom the second TJR was in a noncognate joint , that joint was > 2-fold more likely to be on the contralateral limb than on the ipsilateral limb ( hip to knee P < 0.001 ; knee to hip P = 0.013 ) . In contrast , among the RA cohort , the evolution was r and om and no laterality for noncognate TJR was observed at either the hip or the knee ( P = 0.782 ) . CONCLUSION This characterization of end-stage lower extremity OA demonstrates that the disease evolves nonr and omly ; after 1 joint is replaced , the contralateral limb is significantly more likely to show progression of OA than is the ipsilateral limb . Thus , OA in 1 weight-bearing joint appears to influence the evolution of OA in other joints . The absence of such laterality in RA suggests that OA progression may be mediated by extrinsic factors such as altered joint loading Abstract : The objective of this study was to measure three-dimensional knee motion during gait in patients with total knee replacements which either retained the posterior cruciate ligament ( n = 11 ) , or required sacrifice of the posterior cruciate ligament and replacement of its function with a posterior stabilizing articular surface ( n = 9 ) . Clinical ly meaningful translations ( anterior and posterior , medial and lateral , proximal and distal ) and rotations ( flexion and extension , internal and external rotation , abduction and adduction ) were measured using an instrumented spatial linkage . Although patients from both groups were able to achieve passive full extension and a minimum of 95 ° flexion , some of their translations and rotations during free speed walking were consistently less than those in a group of healthy controls . Motion during the swing phase of gait was similar for both knee replacement groups . However , abduction and adduction and proximal and distal translation were larger ( but neither difference was significant ) for the patients with implants with a posterior stabilizing surface , which suggests that the stabilizing surface may not reliably provide as much stability in these directions as does retention of the posterior cruciate ligament BACKGROUND Clarification of the indications for patellar resurfacing in total knee arthroplasty ( TKA ) is still necessary . Few studies of adequate power have evaluated functional differences between total knee arthroplasty with and without patellar resurfacing , in particular walking gait . This study aim ed to identify clinical ly relevant differences in knee kinematic or kinetic parameters during level walking between total knee arthroplasty with and without patellar resurfacing , after controlling for pre-surgery gait parameters . METHODS Kinematic and kinetic gait analysis of level walking was performed on 34 subjects ( 41 knees ) before and 12 - 18 months after total knee arthroplasty with patellar resurfacing performed r and omly . Linear regression analysis was used to examine the influence of patellar resurfacing upon gait variables whilst controlling for the corresponding pre-surgery measure . FINDINGS The pre-surgery value was a moderate to strong significant predictor of all post-surgery temporal-spatial and kinetic gait parameters ( p < 0.001 - 0.008 ) , and most kinematic parameters ( p < 0.001 - 0.066 ) . The addition of patellar resurfacing to the regression models did not improve the predictive power in any case . Only one parameter , knee flexion at heel-strike , displayed a difference near statistical significance between total knee arthroplasty with and without patellar resurfacing ( 10 degrees versus 7 degrees respectively , p = 0.023 ) . INTERPRETATION Pre-surgery gait patterns are an important determinant of post-surgery gait . There are no clinical ly relevant differences in walking gait between total knee arthroplasty performed with or without patellar resurfacing , using the Profix design 
    Output:
    
Studies indicated smaller peak knee flexion during weight acceptance and less knee flexion excursion in total knee arthroplasty subjects compared to controls .
Knee angle at foot strike was generally similar in arthroplasty groups compared to controls .
Maximum external knee flexion moment was generally lower in arthroplasty groups compared to controls .
Conflicting results were found for other knee moments .
Conclusions Peak knee flexion and knee flexion excursion during weight acceptance are smaller in the operated knee following total knee arthroplasty compared to healthy controls .
There may also be a smaller peak knee flexion moment after arthroplasty compared to controls .
Knee mechanics in the operated knee are not normal after total knee arthroplasty .
Abnormal gait mechanics may predispose the individual to further joint degeneration , particularly in the nonoperated knee .