***TASK*** the task is to summarize an input biomedical literature in six sentences 
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    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: Background Few studies exist that evaluate the effect of partial medial meniscectomy in knees with intact anterior cruciate ligaments . Hypothesis Partial meniscectomy of bucket-h and le medial meniscus tears will cause joint space narrowing . Study Design Case series ; Level of evidence , 4 . Methods Between 1982 and 2001 , 135 patients met the study criteria of a partial medial meniscectomy , intact ligaments , no surgery to the contralateral knee , and no chondromalacia greater than grade II . Seventy-nine patients living within 150 miles of the clinic were asked to return for physical examination .  Joint space narrowing was measured from the middle of the femoral condyle to the middle of the tibial plateau using digitally magnified weightbearing 45 ° flexed posteroanterior and full-extension anteroposterior radiographs . Measurements were performed twice with the observer blinded to the previous measurements . Subjective follow-up was obtained prospect ively on an annual basis with International Knee Documentation Committee and modified Noyes knee question naires . Results Forty-nine patients were examined at a mean of 11.8 years postoperatively . Mean medial joint space narrowing was 1.2 ± 0.5 mm on 45 ° flexed posteroanterior radiograph and 0.2 ± 0.9 mm on full-extension anteroposterior radiographs ( P < . 001 ) . Four patients had 2 mm or more of joint space narrowing . Subjective surveys obtained from 95 patients showed a mean subjective score of 89.9 points . Subjective scores did not decrease through time , and there was no correlation of joint space narrowing to lower subjective scores . Conclusion Partial medial meniscectomy in stable knees causes only mild joint space narrowing ( mean , 1.2 mm ) at a mean 12-year follow-up . Digitally magnified 45 ° flexed posteroanterior radiographs are more likely to demonstrate joint space narrowing than are full-extension anteroposterior radiographs In this prospect i ve r and omised study two treatments after non-traumatic medial meniscal tear diagnosed with radiological examination and magnetic resonance imaging were compared ; arthroscopic partial meniscectomy followed by supervised exercise or supervised exercise alone . The aim was to evaluate knee function and physical activity . Ninety patients ( mean age 56 years ) were evaluated using the  Knee Injury and Osteoarthritis Outcome Score , the Lysholm Knee Scoring Scale , the Tegner Activity Scale and a Visual Analogue Scale for knee pain prior to the intervention , after 8 weeks of exercise and after 6 months . According to the outcome scores arthroscopic partial medial meniscectomy combined with exercise did not lead to greater improvement than exercise alone . After the intervention both groups reported decreased knee pain , improved knee function and a high satisfaction ( P < 0.0001 ) . Forty-one per cent of the patients returned to their pre-injury activity level after 6 months . In conclusion , when evaluated with outcome scores , arthroscopic partial medial meniscectomy followed by supervised exercise was not superior to supervised exercise alone in terms of reduced knee pain , improved knee function and improved quality of life BACKGROUND Recent evidence shows that arthroscopic partial meniscectomy ( APM ) offers no benefit over conservative treatment of patients with a degenerative meniscus tear . However , patients who report mechanical symptoms ( sensations of knee catching or locking ) may benefit from APM . OBJECTIVE To assess whether APM improves mechanical symptoms better than sham surgery . DESIGN R and omized , patient- and outcome assessor-blinded , sham surgery-controlled , multicenter trial . ( Clinical Trials.gov : NCT00549172 ) . SETTING 5 orthopedic clinics in Finl and . PATIENTS Adults ( aged 35 to 65 years ) with a degenerative medial meniscus tear and no knee osteoarthritis . INTERVENTION APM or sham surgery . MEASUREMENTS Patients ' self-report of mechanical symptoms before surgery and at 2 , 6 , and 12 months after surgery . RESULTS 70 patients were r and omly assigned to APM , and 76 were assigned to sham surgery . Thirty-two patients ( 46 % ) in the APM group and 37 ( 49 % ) in the sham surgery group reported catching or locking before surgery ; the corresponding numbers at any follow-up were 34 ( 49 % ) and 33 ( 43 % ) , with a risk difference of 0.03 ( 95 % CI , -0.06 to 0.12 ) . In the subgroup of 69 patients with preoperative catching or locking , the risk difference was 0.07 ( CI , -0.08 to 0.22 ) . LIMITATION Analyses were post hoc , and the results are only generalizable to knee catching and occasional locking because few patients reported other types of mechanical symptoms . CONCLUSION Resection of a torn meniscus has no added benefit over sham surgery to relieve knee catching or occasional locking . These findings question whether mechanical symptoms are caused by a degenerative meniscus tear and prompt caution in using patients ' self-report of these symptoms as an indication for APM . PRIMARY FUNDING SOURCE Academy of Finl and Background — Arthroscopic meniscal surgery is the most common orthopedic procedure , and the incidence has increased in Denmark over the last 10 years . Concomitantly , several r and omized controlled trials have shown no benefit of arthroscopic procedures including arthroscopic partial meniscectomy in middle-aged and older individuals suffering from knee pain with or without knee osteoarthritis . We examined the annual incidence of meniscal procedures together with age , sex , and diagnosis for patients who underwent meniscal procedures in the period 2000–2011 in Denmark . Methods — Data on age , sex , diagnosis , and surgical procedures were extracted from the Danish National Patient Register for the years 2000–2011 , for all records containing meniscal surgery as a primary or secondary procedure . Results — The overall annual incidence of meniscal procedures per 100,000 persons in Denmark doubled from 164 in 2000 to 312 in 2011 ( i.e. 8,750 procedures to 17,368 procedures ) . A 2-fold increase was found for patients aged between 35 and 55 , and a 3-fold increase was found for those older than 55 . Middle-aged and older patients accounted for 75 % of all 151,228 meniscal procedures carried out between 2000 and 2011 . Interpretation — The incidence of meniscal procedures performed in Denmark doubled from 2000 to 2011 , with the largest increase in middle-aged and older patients . This increase contrasts with the mounting evidence showing no added benefit of arthroscopic partial meniscectomy over non-surgical treatments . Our observations illustrate the long delay in the dissemination , acceptance , and implementation of research evidence into the practice of arthroscopic surgery The purpose of this study is to define the clinical features and characteristics of radial tears in the root of the posterior horn of the medial meniscus and to report the outcome of arthroscopic treatment . Arthroscopic meniscus surgery  was performed on 7,148 knees . Of those , 722 ( 10.1 % ) were radial tear in the root of the posterior horn of the medial meniscus . We review ed the medical records from a r and om sample of 67 subjects studied ( mean age 55.8 years , range 38–72 , mean follow-up period 56.7 months , range , 8–123 ) , which included surgical notes and detailed arthroscopic photographs of 70 knees . All patients were treated with arthroscopic partial meniscectomy .  The age distribution , preoperative physical signs , results of magnetic resonance imaging , body mass index , and surgical findings of the study subjects were analyzed and the clinical results were grade d with the Lysholm knee scoring scale and a question naire . Radiologic evaluation consisted of preoperative and at the latest follow-up radiographs . Eighty percent of the patients were older than 50 years , and 80.6 % were either obese or morbidly obese . The mean Lysholm score improved from a preoperative value of 53 to a value of 67 . The average preoperative Kellgren – Lawrence radiograph grade was 2 ( range 0–3 points ) , a value that increased to 3 ( range 2–4 ) at the latest follow-up , which showed a significant worsening . The preoperative MRI was reevaluated after the arthroscopic confirmation of a medial meniscal root tear . A tear could be demonstrated in only 72.9 % of the patients , the rest of whom demonstrated degeneration and /or fluid accumulation at the posterior horn without a visible meniscal tear . Radial tears in the root of the medial meniscal posterior horn , which may not be visible in about one-third of the preoperative MRI scans , are common . That type of meniscal tear is strongly associated with obesity and older age and is morphologically different from the degenerative tears that often occur in the posterior horn . Partial meniscectomy provides symptomatic relief in most cases but does not arrest the progression of radiographically revealed osteoarthritis Background : It is still debated whether a degenerative horizontal tear of the medial meniscus should be treated with surgery . Hypothesis : The clinical outcomes of arthroscopic meniscectomy will be better than those of nonoperative treatment for a degenerative horizontal tear of the medial meniscus . Study Design : R and omized controlled trial ; Level of evidence , 1 . Methods : A total of 102 patients with knee pain and a degenerative horizontal tear of the posterior horn of the medial meniscus on magnetic resonance imaging were included in this study between January 2007 and July 2009 . The study included 81 female and 21 male patients with an average age of 53.8 years ( range , 43 - 62 years ) . Fifty patients underwent arthroscopic meniscectomy ( meniscectomy group ) , and 52 patients underwent nonoperative treatment with strengthening exercises  ( nonoperative group ) . Functional outcomes were compared using a visual analog scale ( VAS ) for pain , Lysholm knee score , Tegner activity scale , and patient subjective knee pain and satisfaction . Radiological evaluations were performed using the Kellgren-Lawrence classification to evaluate osteoarthritic changes . Results : In terms of clinical outcomes , meniscectomy did not provide better functional improvement than nonoperative treatment . At the final follow-up , the average VAS scores were 1.8 ( range , 1 - 5 ) in the meniscectomy group and 1.7 ( range , 1 - 4 ) in the nonoperative group ( P = .675 ) . The average Lysholm knee scores at 2-year follow-up were 83.2 ( range , 52 - 100 ) and 84.3 ( range , 58 - 100 ) in the meniscectomy and nonoperative groups , respectively ( P = .237 ) . In addition , the average Tegner activity scale and subjective satisfaction scores were not significantly different between the 2 groups . Although most patients initially had intense knee pain with mechanical symptoms , both groups reported a relief in knee pain , improved knee function , and a high level of satisfaction with treatment ( P < .05 for all values ) . Two patients in the meniscectomy group and 3 in the nonoperative group with Kellgren-Lawrence grade 1 progressed to grade 2 at the 2-year follow-up . Conclusion : There were no significant differences between arthroscopic meniscectomy and nonoperative management with strengthening exercises in terms of relief in knee pain , improved knee function , or increased satisfaction in patients after 2 years of follow-up BACKGROUND Arthroscopic partial meniscectomy is one of the most common orthopedic procedures , yet rigorous evidence of its efficacy is lacking . METHODS We conducted a multicenter , r and omized , double-blind , sham-controlled trial in 146 patients 35 to 65 years of age who had knee symptoms consistent with a degenerative medial meniscus tear and no knee osteoarthritis . Patients were r and omly assigned to arthroscopic partial meniscectomy or sham surgery . The primary outcomes were changes in the Lysholm and Western Ontario Meniscal Evaluation Tool ( WOMET ) scores ( each ranging from 0 to 100 , with lower scores indicating more severe symptoms ) and in knee pain after exercise ( rated on a scale from 0 to 10 , with 0 denoting no pain ) at 12 months after the procedure . RESULTS In the intention-to-treat analysis , there were no significant between-group differences in the change from baseline to 12 months in any primary outcome . The mean changes ( improvements ) in the primary outcome measures were as follows : Lysholm score , 21.7 points in the partial-meniscectomy group as compared with 23.3 points in the sham-surgery group ( between-group difference , -1.6 points ; 95 % confidence interval [ CI ] , -7.2 to 4.0 ) ; WOMET score , 24.6 and 27.1 points , respectively ( between-group difference , -2.5 points ; 95 % CI , -9.2 to 4.1 ) ; and score for knee pain after exercise , 3.1 and 3.3 points , respectively ( between-group difference , -0.1 ; 95 % CI , -0.9 to 0.7 ) . There were no significant differences between groups in the number of patients who required subsequent knee surgery ( two in the partial- 
    Output:
    
Moderate evidence was found , that the presence of radiological knee osteoarthritis at baseline and longer duration of symptoms ( > 1 year ) are associated with worse clinical outcome following APM .
In addition , resecting > 50 % of meniscal tissue and leaving a non-intact meniscal rim after meniscectomy are intra-articular predictive factors for worse clinical outcome .
Moderate evidence was found that sex , onset of symptoms ( acute or chronic ) , tear type or preoperative sport level are not predictors for clinical outcome .
Conflicting evidence was found for the prognostic value of age , perioperative chondral damage , body mass index and leg alignment .
Summary / conclusion Long duration of symptoms ( > 1 year ) , radiological knee osteoarthritis and resecting > 50 % of meniscus are associated with a worse clinical outcome following APM .