***TASK*** the task is to summarize an input biomedical literature in six sentences 
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    Input: Background The primary purpose of this r and omized controlled trial ( RCT ) was to compare knee-specific outcomes ( stiffness , pain , function ) between patellar retention and resurfacing up to 10 years after primary total knee arthroplasty ( TKA ) . Secondarily , we compared re-operation rates . Methods 38 subjects with non-inflammatory arthritis were r and omized at primary TKA surgery to receive patellar resurfacing ( n = 21 ; Resurfaced group ) or to retain their native patella ( n = 17 ; Non-resurfaced group ) . Evaluations were performed preoperatively , one , five and 10 years postoperatively by an evaluator who was blinded to group allocation . Self-reported knee-specific stiffness , pain and function , the primary outcomes , were measured by the Western Ontario McMaster Osteoarthritis Index ( WOMAC ) . Revision rate was determined at each evaluation and through hospital record review . Results 30 ( 88 % ) and 23 ( 72 % ) of available subjects completed the five and 10-year review respectively . Knee-specific scores continued to improve for both groups over the 10-years , despite diminishing overall health with no significant group differences seen . All revisions occurred within five years of surgery ( three Non-resurfaced subjects ; one Resurfaced subject ) ( p = 0.31 ) . Two revisions in the Non-resurfaced group were due to persistent anterior knee pain . Conclusions We found no differences in knee-specific results between groups at 5–10 years postoperatively . The Non-resurfaced group had two revisions due to anterior knee pain similar to rates reported in other studies . Knee-specific results provide useful postoperative information and should be used in future studies comparing patellar management strategies . Clinical Trials.gov During a two-year period , eighty-nine patients who were scheduled to have a total knee arthroplasty for the treatment of degenerative osteoarthrosis were r and omly assigned to one of two groups : resurfacing of the patella or retention of the patella . All patients received the same  posterior cruciate-sparing prosthesis  , and all operations were performed by , or under the direct supervision of , one of us . Three patients died in the early postoperative period . The remaining eighty-six patients ( 118 knees ; fifty-eight that had had resurfacing of the patella and sixty that had not ) formed the study group . They were followed for a mean of thirty months ( range , twenty-four to forty-four months ) . Evaluation was performed with use of the clinical scoring system of The Knee Society , a patient-satisfaction question naire , specific questions regarding patellofemoral symptoms and function , and radiographs . All clinical evaluations were performed by the same research nurse , without the involvement of a physician , in a blinded manner ( neither the nurse nor the patient had knowledge of whether the patella had been resurfaced ) . Preoperatively , the mean Knee Society score , on a scale ranging from 0 to 200 points , was 89.7 points ( range , 33 to 132 points ) ; postoperatively , this score improved to a mean of 172.7 points ( range , 98 to 200 points ) . With the numbers available for study , we could detect no significant difference between the knees that had had patellar resurfacing and those that had not with regard to the over-all score ( p = 0.63 ) , the subscore for pain ( p = 0.56 ) , or the subscore for function ( p = 0.77 ) . We also could detect no difference between the treatment groups , with the numbers available , with regard to patient satisfaction or the responses to questions involving the function of the patellofemoral joint , including the ability to exit from an automobile , to rise from a chair , and to climb stairs .  Thirty-two patients had bilateral total knee replacement with resurfacing of the patella in one knee and retention of the patella in the other . These patients expressed no clear preference for either knee . Eight ( 13 per cent ) of the sixty knees that had not had resurfacing were painful anteriorly compared with four ( 7 per cent ) of the fifty-eight that had ; this was not a significant difference ( p = 0.38 ) , with the numbers available . The anterior pain that was noted postoperatively was predominantly of new onset ; it had not been observed preoperatively in three of the four knees that had had resurfacing or in four of the eight that had not . No additional treatment options were offered to the patients who had anterior pain in the knee after resurfacing . However , six ( 10 per cent ) of the sixty knees that had not had resurfacing had it subsequently , because of anterior pain in the knee , after the twelfth postoperative month ( range , fifteen to thirty-nine months ) . The pain decreased in four of these knees . Thus , total knee arthroplasty with retention of the patella yielded clinical results that were comparable with those after total knee arthroplasty with patellar resurfacing , but it was associated with a 10 per cent prevalence of the need for subsequent resurfacing . The prevalence of anterior pain after total knee arthroplasty was not influenced by whether or not the patella had been resurfaced . The postoperative clinical scores , the postoperative development of anterior pain , and the need for subsequent resurfacing were not predicted by the presence of preoperative anterior pain , obesity , or the grade of chondromalacia observed intraoperatively . Because of the short duration of follow-up , these results should be considered preliminary . Additional follow-up is planned BACKGROUND The need for patella resurfacing remains an area of considerable controversy in total knee replacement surgery . There would appear to be no reported evidence on the effect of patella resurfacing on knee function , as measured by functional range of movement used in a series of tasks , in patients undergoing knee replacement . The object of this study was to measure knee joint motion during functional activities both prior to and following total knee replacement in a r and omised group of patients with and without patella resurfacing and to compare these patient groups with a group of normal age-matched subjects . METHODS The study design was a double blinded , r and omised , prospect i ve , controlled trial . The knee joint functional ranges of movement of a group of patients ( n=50 , mean age=70 years ) with knee osteoarthritis were investigated prior to and following total knee arthroplasty ( 4 months and 18 - 24 months ) along with a group of normal subjects ( n=20 , mean age=67 ) . Patients were r and omly allocated into two groups , those who received patella resurfacing ( n=25 ) and those who did not ( n=25 ) . Flexible electrogoniometry was used to measure the flexion-extension angle of the knees with respect to time in eleven functional activities . FINDINGS No statistically significant differences ( alpha level 0.05 ) in joint excursion of the affected knee were found between patients who received patella resurfacing and those who did not . INTERPRETATION Routine patella resurfacing in a typical knee arthroplasty population does not result in an increase in the functional range of movement used after knee replacement Patellar resurfacing during total knee arthroplasty ( TKA ) is an actively debated issue . This prospect i ve study addresses fundamental questions regarding whether to resurface the patella . To do this , we compared clinical results of Scorpio PS knees with and without patellar resurfacing  to determine whether there was any statistically significant difference in survivorship , function , pain , and radiographic analyses . Our study failed to demonstrate any statistical difference between the 2 groups ( resurfaced versus nonresurfaced ) according to knee pain , walking abilities , stair climbing , range of motion , and radiologic findings , as well as cross-correlations between patellar pain and age , gender , obesity , or etiology . Our radiologic findings did not reveal any failures of bony structures facing the metallic flange . Some knee design s can thus be seen as " patella friendly . " Given the significant cost of patella resurfacing and the result ing well-known complications , we continue to avoid systematic resurfacing of the patella during Scorpio TKA Complications of patellar resurfacing in total knee arthroplasty have rekindled the interest of many surgeons in patellar retention . In a prospect i ve study 20 r and omly selected patients of 40 underwent patellar resurfacing in combination with their total knee arthroplasty .  The other 20 patients were left with an unresurfaced patella . Within 24 months of follow-up , the advantages of patellar resurfacing could be seen according to the Knee Society Score . Especially in advanced osteoarthritis of the knee joint , the patients achieved better scores in climbing stairs and in function . The superior functional results are arguments for patellar resurfacing , at least in knees with advanced osteoarthritis OBJECTIVE The aim is of this prospect i ve r and omised study was to investigate the necessity of resurfacing the patella in combination with total knee arthroplasty in patients without or mild anterior knee pain before undergoing total knee replacement .  METHODS Between May 1999 and May 2000 fifty patients were enrolled in a prospect i ve , r and omised study . All patients received the same posterior-cruciate-sparing total knee replacement and were r and omised to treatment with and without resurfacing of the patella .  Inclusion criteria were primary osteoarthritis of the knee , preoperatively no pain when the patella was shifted during clinical examination , a maximal grade III radiological degeneration of the patella according to Sperner et al. and at most a mild anterior knee pain in preoperative interview . Evaluations consisted of the determination of the Knee Society clinical score , the completion of a patient satisfaction question naire , and radiographic assessment basing on the Knee Society roentgenographic evaluation and scoring system . All patients were examined preoperatively and 3 , 6 , and 12 months postoperatively . RESULTS In all postoperative examinations patients with patella resurfacing demonstrated a higher overall Knee Society score . At month 6 the difference was statistically significant . The patient satisfaction question naire demonstrated no significant difference between both groups . However , regarding to relief of anterior knee pain and improvement of pain in general patients with nonresurfacing were less satisfied at all follow-ups . Furthermore , after 12 months all answers to the patient satisfaction question naire of the resurfaced group were better . Patella-associated revisions were performed in two patients without resurfacing . Radiographic analysis demonstrated no loosening , fracture , subluxation or dislocation . CONCLUSION The presented study demonstrated after one year follow-up a better functional result , a higher degree of contentment and fewer complications after total knee replacement with patella resurfacing in patients without or mild preoperative anterior knee pain Patellar resurfacing is a controversial issue in primary total knee replacement . So , we took advantage of a large study to try and answer this question . An open prospect i ve multicentric study was conducted about the outcome of the  Nex Gen Total Knee prosthesis  with clinical and radiological follow-up at regular intervals ( 1 , 2 and 5 years ) . The data were central ly collected and analyzed by independent observers . A total of whole 5,915 cases were included ( 487 in the French group ) ; incidences of patello-femoral pain were observed in both French and international groups and compared between cases with or without resurfaced patellae . Only osteoarthritic cases were selected for this particular study . Statistical analysis was performed using a Pearson ’s Chi-square test with a 95 % confidence interval . The frequency of preoperative pain was significantly higher in the French group ; 85.1 % versus 66.6 % ( p<0.05 ) . No patello-femoral pain appeared in preoperatively painless patients in the French group . The frequency of lateral patellar release was similar in both groups . 35.7 % of the patellae were resurfaced in the international group versus 98.8 % in the French one . At 2 years , patello-femoral pain was observed in 6.3 % of cases in the former group versus 0.7 % in the latter one . The risk of having patello-femoral pain was 9.45 times higher in the international group . When considering resurfaced cases in both groups the risk of having anterior knee pain was not significantly different ( p=0.35 ) . In the French group , one case out of nine ( 11.1 % ) with patello-femoral pain had not been resurfaced , while 129 cases out of 151 ( 85.4 % ) had not had a resurfacing in the international group . This emphasizes the effect of patellar implant on pain . Although patello-femoral pain is multifactorial , this analysis tool is powerful in getting rid of the “ center effect ” ( cf Swedish register ) . Even if a longer follow-up for confirmation is needed , our data favor patellar resurfacing with this type of implant in spite of the fact that the trochlear design was considered as anatomical Background : Whether to resurface the patella during a primary total knee arthroplasty performed for the treatment of degenerative osteoarthritis remains a controversial issue . Parameters that have been suggested as being useful in guiding this decision include patient height and weight , the presence of anterior knee pain preoperatively , and the grade of chondromalacia encountered intraoperatively . The purpose of this study was to determine whether these parameters were predictive of the clinical result following total knee arthroplasty with or without patellar resurfacing . Methods : Eighty-six patients ( 118 knees ) undergoing primary total knee arthroplasty for the treatment of osteoarthritis were enrolled in a prospect i ve , r and omized , double-blind study . All patients received the same posterior-cru 
    Output:
    
The most relevant meta- analysis reported no differences in functional scores and incidence of anterior knee pain between the groups .
Conclusions Comparable outcomes were found when comparing patellar resurfacing and non-resurfacing in TKA .
The higher risk of re-operations after non-resurfacing should be interpreted with caution due to the method ological limitations of the meta-analyses regarding search criteria , heterogeneity and the inherent bias of easier indication to reoperation when the patella is not resurfaced .
There is no clear superiority of patellar resurfacing compared to patellar retention .