***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: OBJECTIVE To determine whether hip abductor and adductor muscle strengthening reduces medial compartment knee load and improves symptoms in people with medial tibiofemoral OA and varus malalignment . METHODS In a r and omised controlled trial , 89 participants were r and omly allocated to a hip strengthening group or to a control group with no intervention . The strengthening group performed a physiotherapist-supervised home exercise program targeting the hip abductor and adductor muscles for 12 weeks . The primary outcome was the peak external knee adduction moment measured using three-dimensional gait analysis by a blinded assessor . Secondary outcomes included a pain numeric rating scale , Western Ontario and McMaster Universities Osteoarthritis Index , step test , stair climb test , maximum isometric strength of hip and quadriceps muscles and participant-perceived rating of overall change . Intention-to-treat analyses were performed using linear regression modelling adjusting for baseline outcomes and other characteristics . RESULTS The trial was completed by 76/89 participants ( 85 % ) . There was no significant between-group difference in change in the knee adduction moment [ mean difference ( 95 % confidence interval ( CI ) ) 0.134 ( -0.069 to 0.337 ) Nm/BW x HT% ] . All pain , physical function and muscle strength measures showed significantly greater improvement in the strengthening group ( all P<0.05 ) . The relative risk ( 95 % CI ) of participant-perceived overall improvement in the strengthening group compared to the control group was 20.02 ( 6.21 - 64.47 ) . CONCLUSIONS Although strengthening the hip muscles improved symptoms and function in this patient group , it did not affect medial knee load as measured by the knee adduction moment . Thus it is unlikely that hip muscle strengthening influences structural disease progression . TRIAL REGISTRATION ACTR12607000001493 Background / rationale Although TKA reliably reduces pain from knee osteoarthritis , full recovery of muscle strength and physical function to normal levels is rare . We presumed that a better underst and ing of acute changes in hamstrings and quadriceps muscle performance would allow us to enhance early rehabilitation after TKA and improve long-term function . Questions / purpose sThe purpose s of this study were to ( 1 ) evaluate postoperative quadriceps and hamstrings muscle strength loss after TKA and subsequent recovery using the nonoperative legs and healthy control legs for comparison , and ( 2 ) measure hamstrings coactivation before and after TKA during a maximal isometric quadriceps muscle contraction and compare with nonoperative and healthy control legs . Methods We prospect ively followed 30 patients undergoing TKA at 2 weeks preoperatively and 1 , 3 , and 6 months postoperatively and compared patient outcomes with a cross-sectional cohort of 15 healthy older adults . Bilateral , isometric strength of the quadriceps and hamstrings was assessed along with EMG measures of hamstrings coactivation during a maximal isometric quadriceps contraction . Results There were no differences in strength loss or recovery between the quadriceps and hamstrings muscles of the operative leg throughout the followup , although differences existed when compared with nonoperative and healthy control legs . Hamstrings muscle coactivation in the operative leg during a maximal quadriceps effort was elevated at 1 month ( 144.5 % ) compared to the nonoperative leg . Conclusions Although quadriceps dysfunction after TKA typically is recognized and addressed in postoperative therapy protocol s , hamstrings dysfunction also is present and should be addressed . Clinical Relevance Quadriceps and hamstrings muscle strengthening should be the focus of future rehabilitation programs to optimize muscle function and long-term outcomes OBJECTIVE To evaluate the maximal voluntary contraction ( MVC ) force and the voluntary activation of the quadriceps femoris muscle in patients with knee osteoarthritis ( OA ) before and after total knee arthroplasty ( TKA ) . DESIGN A prospect i ve intervention study . SETTING University hospital clinic in Germany . PATIENTS Fifty patients ( 32 women , 18 men ; mean age + /- st and ard deviation , 65.8+/-5.6 y ) with knee OA and 23 healthy age- and gender-matched control subjects . INTERVENTION Unilateral TKA without patella resurfacing . MAIN OUTCOME MEASURES Voluntary activation , MVC , and true maximal contraction forces of the bilateral quadriceps femoris muscles , using the twitch interpolation technique before and 33+/-8 months after TKA . Assessment of postoperative knee pain by the Lewis score . RESULTS Voluntary activation increased bilaterally after surgery ( P<.01 operated side , P=.02 nonoperated side ) but remained lower than the voluntary activation of the controls . MVC ( P<.001 ) and true maximal contraction forces ( P=.01 ) increased significantly on the operated side . MVC remained unchanged ( P=.45 ) , and true maximal contraction forces decreased significantly ( P=.04 ) on the nonoperated side . CONCLUSION Patients with knee OA have significant bilateral voluntary activation deficits that are , at least in part , reversible within 3 years after TKA . Rehabilitation programs immediately after TKA should focus on reduction of voluntary activation deficits . After voluntary activation improves , physical therapy should target the augmentation of quadriceps femoris muscle strength OBJECTIVE : To test the feasibility of creating a valid and reliable checklist with the following features : appropriate for assessing both r and omised and non-r and omised studies ; provision of both an overall score for study quality and a profile of scores not only for the quality of reporting , internal validity ( bias and confounding ) and power , but also for external validity . DESIGN : A pilot version was first developed , based on epidemiological principles , review s , and existing checklists for r and omised studies . Face and content validity were assessed by three experienced review ers and reliability was determined using two raters assessing 10 r and omised and 10 non-r and omised studies . Using different raters , the checklist was revised and tested for internal consistency ( Kuder-Richardson 20 ) , test-retest and inter-rater reliability ( Spearman correlation coefficient and sign rank test ; kappa statistics ) , criterion validity , and respondent burden . MAIN RESULTS : The performance of the checklist improved considerably after revision of a pilot version . The Quality Index had high internal consistency ( KR-20 : 0.89 ) as did the subscales apart from external validity ( KR-20 : 0.54 ) . Test-retest ( r 0.88 ) and inter-rater ( r 0.75 ) reliability of the Quality Index were good . Reliability of the subscales varied from good ( bias ) to poor ( external validity ) . The Quality Index correlated highly with an existing , established instrument for assessing r and omised studies ( r 0.90 ) . There was little difference between its performance with non-r and omised and with r and omised studies . Raters took about 20 minutes to assess each paper ( range 10 to 45 minutes ) . CONCLUSIONS : This study has shown that it is feasible to develop a checklist that can be used to assess the method ological quality not only of r and omised controlled trials but also non-r and omised studies . It has also shown that it is possible to produce a checklist that provides a profile of the paper , alerting review ers to its particular method ological strengths and weaknesses . Further work is required to improve the checklist and the training of raters in the assessment of external validity The purpose of the present prospect i ve intervention study was to evaluate voluntary isometric force production , relaxation and activation capacity of the quadriceps femoris ( QF ) muscle before and 6 months after unilateral total knee arthroplasty ( TKA ) . TKA was performed in ten women with primary knee osteoarthritis ( OA ) using the condular endoprostheses .  Isometric maximal voluntary contraction ( MVC ) force , rate of force development at 50 % of MVC ( RFD50 ) and their ratio to body mass , half-relaxation time ( HRT ) and voluntary activation ( VA ) of the QF muscle were recorded in patients for operated and non-operated leg before and 6 months after TKA . Established characteristics were compared with data on the dominant leg of ten age- and gender-matched controls . The clinical examination was performed using the Knee Society System ( KSS ) scores and pain intensity was assessed by visual analogue scale . MVC force in operated leg was lower ( P < 0.05 ) before and 6 months after TKA as compared with the non-operated leg ( 31 and 32 % , respectively ) and controls ( 48 and 44 % , respectively ) . Patients had lower ( P < 0.05 ) VA of the QF muscle in operated leg 6 months after TKA as compared to controls . Significant increase ( P < 0.05 ) of KSS clinical scores and the tendency for the increasing of explosive force production of QF muscle in the operated leg were observed 6 months after TKA ( RFD50 was 60 % lower before TKA and 40 % lower 6 months after surgery as compared to controls ) . When compared with the preoperative value , HRT prolongation ( P < 0.05 ) was noted 6 months after TKA in QF muscle of both legs in patients . Therefore , the present study confirmed that patients with knee OA had reduced force generation ability of QF muscle before TKA and the improvement of explosive force was noted 6 months after surgery OBJECTIVE While joint arthroplasty improves the functional ability of persons with severe knee osteoarthritis ( OA ) , the long-term effects of surgical intervention on body mass have not been evaluated . The objective of this study was to determine if a reduction in body mass index ( BMI ) was present following unilateral total knee arthroplasty ( TKA ) compared to an age-matched healthy control group who did not have surgery . METHOD One hundred and six adults with unilateral , end-stage knee OA and thirty-one persons without knee pain participated in the prospect i ve longitudinal study . Subjects with OA underwent primary unilateral TKA and received post-operative out-patient physical therapy . Height , weight , quadriceps strength and self-perceived functional ability were measured at baseline and at a 2-year follow-up . RESULTS There was a significant interaction effect between body mass over time and subject group ( P=0.017 ) . BMI showed a significant increase over 2 years for the surgical group ( P<0.001 ) , but not for the control group ( P=0.842 ) . Sixty-six percent of the persons in the surgical group gained weight over the 2 years with an average weight gain of 6.4 kg , or 14 pounds , 2 years after their initial physical therapy visit . Educational level , marital status , income level and activity level prior to surgery were not related to post-surgical weight gain . CONCLUSION The majority of subjects gain weight after surgery and this can not be attributed to the effects of aging . Weight gain after TKA should be treated as an independent concern and management of orthopedic impairments will not result in weight loss . Post-operative care should include access to nutrition or weight management professionals in addition to medical and physical therapy services BACKGROUND It is reported that a majority of the patients with knee osteoarthritis have cartilage degeneration in medial and patellofemoral compartments . A bi-compartmental knee replacement system was design ed to treat osteoarthritis at medial and patellofemoral compartments . To date , there is very little information regarding the knee mechanics during gait after bi-compartmental knee replacement . The purpose of the study was to evaluate knee strength and mechanics during level walking after knee replacement . METHODS Ten healthy control subjects and eight patients with unilateral bi-compartmental knee replacement participated in the study .  Maximal isokinetic concentric knee extension strength was evaluated . 3D kinematic and kinetic analyses were conducted for level walking . Paired Student t-test was used to determine difference between surgical and non-involved limbs . One way MANOVA was used to determine difference between surgical and control groups . FINDINGS The surgical knee exhibited less peak torque and initial abduction moment than both the non-involved and control limbs ( P<0.05 ) . The non-involved limb had less knee extension at stance and greater knee extensor moment during push-off than both the surgical and control limbs ( P<0.05 ) . No differences were found for other typical knee mechanics among the surgical , non-involved , and control limbs during walking ( P>0.05 ) . INTERPRETATIONS Patients with bi-compartmental knee replacement exhibited good frontal plane knee mechanics and were able to produce the same level of knee extensor moment as healthy control limbs during walking . While showing some compensatory patterns during walking , patients with bi-compartmental knee replacement largely exhibited normal gait patterns and knee mechanics We performed a single-center , r and omized , double-blind study to compare muscle strength in patients who had undergone primary total knee arthroplasty ( TKA ) , performed using either a minimally invasive or a conventional surgical technique . We evaluated 30 knees in healthy age-matched subjects , 22 knees after conventional TKA ( conventional group ) , and 23 knees after minimally invasive surgery TKA ( MIS group ) .  The Hospital for Special Surgery ( HSS ) score , Oxford knee score ( OKS ) , and isokinetic ( 60º/s ) muscle strength were evaluated the day before surgery and 3 , 6 , and 12 months after surgery . HSS and OKS improved significantly over time during follow-up ( p<0.001 ) , but there was no significant difference between the groups ( p>0.05 ) . The extensor peak torque 
    Output:
    
There was low quality evidence of quadriceps and hamstring weakness following TKA .