***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 
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    Input: 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 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 : 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-cruciate-sparing total knee prosthetic components . Patients were r and omized to treatment with or without resurfacing of the patella . Evaluations consisted of the determination of a Knee Society clinical score , the completion of a patient satisfaction question naire , specific questions relating to patellofemoral symptoms , and radiographs .  Sixty-seven patients ( ninety-three knees ) were followed for a minimum of five years ( range , sixty to eighty-four months ; average , 70.5 months ) . Results : With the numbers available , there was no significant difference between the groups treated with and without resurfacing with regard to the overall Knee Society score or the pain and function subscores . Obesity , the degree of patellar chondromalacia , and the presence of preoperative anterior knee pain did not predict postoperative clinical scores or the presence of postoperative anterior knee pain . Conclusions : The occurrence of anterior knee pain could not be predicted with any clinical or radiographic parameter studied . On the basis of these results , it seems likely that postoperative anterior knee pain is related either to the component design or to the details of the surgical technique , such as component rotation , rather than to whether or not the patella is resurfaced The effect of  total knee arthroplasty design on  extensor mechanism function was evaluated prospect ively in a consecutive , single-surgeon series . Group 1 knees ( n = 83 ) were implanted with a prosthesis that has a multiradius femoral component , and group 2 knees ( n = 101 ) were implanted with a femoral prosthesis that has a single flexion-extension axis . Group 2 knees gained flexion more rapidly : At 6 weeks , the average flexion for was 94.5 degrees for group 1 and 107.1 degrees for group 2 ( P<.001 ) . Significantly more patients with group 2 knees were able to arise from a 16-inch ( low ) chair without using their arms starting at 6 weeks , and a difference was maintained through 2 years ( 90 % vs 73 % ; P=.003 ) . Patients with group 2 knees had significantly less anterior knee pain when rising from a seated position starting at 6 weeks , and a difference was maintained through 2 years ( 1 % vs 22 % ; P=.001 ) The aim of this study was to assess medium term results of patellar resurfacing in total knee arthroplasty , specifically looking at anterior knee pain , patellofemoral function and need for reoperation . A prospect i ve cohort study was conducted with patients undergoing staged bilateral knee arthroplasty with the patella being resurfaced only on one side . This was due to change in the clinical practice of the senior author . Sixty patients were review ed clinical ly and radiologically on a regular basis . The surgery was either performed or supervised by the senior author in all cases . All patients received the cemented press-fit condylar © prosthesis . The Knee Society clinical rating system was used . Scores were recorded pre-operatively and post-operatively at three months , one year , two years and three yearly thereafter . The mean age of patients in the study group was 75 years ( range : 62–89 years ) . There were 42 women and 18 men in the study . The mean duration of follow-up was 4.5 years ( range : 2–12 years ) . There was no significant difference in the pre-operative scores in both groups . There were significantly better scores ( p < 0.05 ) on the resurfaced side as compared to the non-resurfaced side at final follow-up . No revision was carried out for patellofemoral complications on the resurfaced side . Four patients required revision in the form of patellar resurfacing on the non-resurfaced side for persistent anterior knee pain .  Patellar resurfacing is recommended in total knee arthroplasty for better functional outcome with regards to anterior knee pain and patellofemoral function To describe the natural history of pain after total knee arthroplasty and to identify factors predicting excessive postoperative pain , we used a prospect i ve , observational study assessing clinical and radiographic variables preoperatively and at 1 , 3 , 6 , and 12 months after knee replacement .  Data sources included the visual analog pain scale and other measures of patient health , psychologic state , and component reliability . Regression analyses were conducted to identify specific factors predictive of postoperative pain , controlling for ine quality of variables , and confirmed using regression diagnostics . For 116 patients ( 149 knees ; mean age , 66 years ; 55.2 % women ) , significant pain was reported by 72.3 % , 44.4 % , 22.6 % , 18.4 % , and 13.1 % , respectively . No intergroup differences existed for anesthesia , weight , age , or gender . Patients with greater preoperative pain had more postoperative pain , used more home therapy , and postoperative manipulations . Preoperative depression and anxiety were associated with heightened pain at 1 year . Pain after knee replacement resolves quickly , declining to approximately 1/2 by 3 months . However , one in eight patients report moderate to severe pain 1 year after surgery despite an absence of clinical or radiographic abnormalities . Development of office-based preoperative screening tools and interventions for these patients may reduce postoperative costs and improve patient-perceived outcomes Patellofemoral problems are a common cause of morbidity and reoperation after total knee arthroplasty . We made a prospect i ve study of 52 patients who had bilateral arthroplasty ( 104 knees ) and in whom the patella was resurfaced on one side and not on the other . A movable-bearing prosthesis with an anatomical femoral groove was implanted on both sides by the same surgeon using an otherwise identical technique . The mean follow-up was 5.24 years ( 2 to 10 ) . In the 30 available patients ( 60 knees ) there was no difference between the two sides in subjective preference , performance on ascending and descending stairs or the incidence of anterior knee pain . Radiographs showed no differences in prosthetic alignment , femoral condylar height , patellar congruency or joint line position . The use of an appropriate prosthetic design and careful surgical technique can provide equivalent results after knee arthroplasty with or without patellar resurfacing . Given the indications and criteria , which we discuss , retention of the patellar surface is an acceptable option Patellar resurfacing in total knee arthroplasty remains controversial . This study compared the long-term clinical outcomes of total knee arthroplasties performed with and without the patella resurfaced and is an up date of a previous report . Eighty-six patients ( 118 knees ) underwent primary total knee replacement  and were r and omized into two groups : those treated with and those treated without resurfacing of the patella . Outcomes included the scores according to the Knee Society clinical rating system , the scores according to a forty-one- question patellofemoral-specific patient question naire , patient satisfaction , global and anterior knee pain scores , radiographic findings , and complications and revisions .  Fifty-seven patients ( seventy-eight knees ) were followed for a minimum of ten years . No significant differences were identified between the two groups in terms of the range of motion , Knee Society scores , satisfaction , global knee pain , or anterior knee pain . The overall revision rates in the original series of 118 knees were 12 % in the nonresurfacing group and 9 % in the resurfacing group . Seven patients ( 12 % ) in the nonresurfacing group and two patients ( 3 % ) in the resurfacing group underwent revision for a reason related to a patellofemoral problem . On the basis of these findings , we concluded that , with the type of total knee arthroplasty used in our patients , similar results may be achieved with and without patellar resurfacing To find out the improvement 
    Output:
    
A weak correlation with AKP was found for specific retained presurgery gait patterns .
A weak recommendation can be given for the use of femoral components with a posterior centre of rotation , resection of Hoffa ’s fat pad , patellar rim electrocautery , and preventing combined component internal rotation .
The correlation between postsurgical AKP and the degree of patellar cartilage wear , tibial component bearing strategies , and patellar resurfacing is inconclusive .