***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: Background One of the rationale s behind using strength training in the treatment of adolescents with Patellofemoral Pain ( PFP ) is that reduced strength of the lower extremity is a risk factor for PFP and a common deficit . This rationale is based on research conducted on adolescents > 15 years of age but has never been investigated among young adolescents with PFP . Objectives To compare isometric muscle strength of the lower extremity among adolescents with PFP compared to age- and gender-matched pain-free adolescents . Methods In 2011 a population -based cohort ( APA2011-cohort ) consisting of 768 adolescents aged 12–15 years from 8 local schools was formed . In September 2012 , all adolescents who reported knee pain in September 2011 were offered a clinical examination if they still had knee pain . From these , 20 adolescents ( 16 females ) were diagnosed with PFP . Pain-free adolescents from the APA2011-cohort ( n = 20 ) were recruited on r and om basis as age- and gender-matched pairs . Primary outcome was isometric knee extension strength normalized to body weight ( % BW ) and blinded towards subject information . Secondary outcomes included knee flexion , hip abduction/adduction and hip internal/external rotation strength . Demographic data included Knee Injury and Osteoarthritis Outcome Score ( KOOS ) and symptom duration . Results Adolescents with PFP reported long symptom duration and significantly worse KOOS scores compared to pain-free adolescents . There were no significant differences in isometric knee extension strength ( Δ0.3 % BW , p = 0.97 ) , isometric knee flexion strength ( Δ0.4 % BW , p = 0.84 ) or different measures of hip strength ( Δ0.4 to 1.1 % BW , p>0.35 ) . Conclusion Young symptomatic adolescents with PFP between 12 and 16 years of age did not have decreased isometric muscle strength of the knee and hip . These results question the rationale of targeting strength deficits in the treatment of adolescents with PFP . However , strength training may still be an effective treatment for those individuals with PFP suffering from strength deficits Objectives Describe proportions of individuals with patellofemoral pain ( PFP ) with an unfavourable recovery over 12 months ; identify clinical predictors of poor recovery at 3 and 12 months ; and determine baseline values of predictors that identify those with poor 12-month prognosis . Methods An observational analysis utilised data from 310 individuals with PFP enrolled in two r and omised clinical trials . Thirteen baseline variables ( participant , PFP , study characteristics ) were investigated for their prognostic ability . Pain , function and global recovery were measured at 3 and 12 months . Multivariate backward stepwise regression analyses ( treatment-adjusted , p<0.10 ) were performed for each follow-up measure . Receiver operator characteristic curves identified cut-points associated with unfavourable recovery at 12 months . Results 55 % and 40 % of participants had an unfavourable recovery at 3 and 12 months , respectively . Longer baseline pain duration was significantly associated with poor 3-month and 12-month recovery on measures of pain severity ( β 11.36 to 24.94 ) , Anterior Knee Pain ( AKP ) Scale ( −4.44 to −11.33 ) and global recovery ( OR : 2.32 to 6.11 ) . Greater baseline pain severity and lower AKP Scale score were significantly associated with poor recovery on multiple measures ( p<0.05 ) . Baseline duration > 2 months and AKP Scale score < 70/100 were associated with unfavourable 12-month recovery . Conclusions A substantial number of individuals with PFP have an unfavourable recovery over 12 months , irrespective of intervention . Knee pain duration > 2 months is the most consistent prognostic indicator , followed by AKP Scale score < 70 . Sports medicine practitioners should utilise interventions with known efficacy in reducing PFP , and promote early intervention to maximise prognosis . Trial registration Australian study : Australian Clinical Trials Registry ( ACTRN012605000463673 ) , Clinical Trials.gov ( NCT00118521 ) ; Dutch study : International St and ard R and omised Controlled Trial Number Register ( IS RCT N83938749 Purpose The purpose of the study was to investigate if changes in psychological variables are related to the outcome in pain and disability in patients with chronic anterior knee pain . Methods A longitudinal observational study on 47 patients with chronic anterior knee pain was performed in a secondary healthcare setting .  Pain was measured with the visual analogue scale and disability with the Lysholm scale . The psychological variables , such as anxiety , depression , pain coping strategies , catastrophizing and fear to movement beliefs , were studied by using self-administered question naires . Results Among the pain coping strategies , only the catastrophizing subscale showed a significant reduction . Similarly , anxiety , depression and kinesiophobia were significantly reduced after treatment . Those patients who decreased the catastrophizing , kinesiophobia , anxiety and depression showed a greater improvement in pain and disability after a purely biomedical treatment . A multiple regression analysis revealed that changes in catastrophizing predicted the amount of improvement in pain severity and that changes in both catastrophizing and anxiety predicted changes in disability after treatment . Conclusion What has been found suggests that clinical improvement in pain and disability is associated with a reduction in catastrophizing and kinesiophobia . Therefore , co- interventions to reduce catastrophizing thinking and kinesiophobia may enhance the results .Level of evidence Prospect i ve Cohort Study , Level I for prognosis AIM To study the prevalence of persistent post-surgical pain ( PPSP ) and neuropathic pain ( NP ) after total knee replacement ( TKR ) . METHODS MEDLINE and Embase data bases were search ed for articles published until December 2014 in English language . Published articles were included if they referred to pain that lasts at least 3 mo after primary TKR for knee osteoarthritis , and measured pain with pain specific instruments . Studies that referred to pain caused by septic reasons and implant malalignment were excluded . Both prospect i ve and retrospective studies were included and only 14 studies that match the inclusion criteria were selected for this review . RESULTS The included studies were characterized by the heterogeneity on the scales used to measure pain and pre-operative factors related to PPSP and NP . The reported prevalence of PPSP and NP seems to be relatively high , but it varies among different studies . There is also evidence that the prevalence of post-surgical pain is related to the scale used for pain measurement . The prevalence of PPSP is ranging at 6 mo from 16 % to 39 % and at 12 mo from 13.1 % to 23 % and even 38 % of the patients . The prevalence of NP at 6 mo post-operatively is ranging from 5.2 % to 13 % . Pre-operative factors related to the development of PPSP also differ , including emotional functioning , such as depression and pain catastrophizing , number of comorbidities , pain problems elsewhere and operations in knees with early grade of osteoarthritis . CONCLUSION No firm conclusions can be reached regarding the prevalence of PPSP and NP and the related factors due to the heterogeneity of the studies & NA ; Few studies have investigated whether prognostic indicators , which contribute to the transition from acute to chronic low back pain ( LBP ) , are also those which contribute to continuing persistence of chronic LBP . We compared the contribution of physical , psychological and social indicators to predicting disability after one year between consulters with LBP of less than 3 months duration and more than 3 months duration . Data from two large prospect i ve cohort studies of consecutive patients consulting with LBP in general practice s were merged , providing complete data for 258 cases with acute/subacute LBP and 668 cases with chronic LBP at 12 months follow‐up . There were significant differences between the two LBP groups in baseline characteristics and clinical course of disability , assessed by Rol and Morris Disability Question naire , during the year of follow‐up . Adjusted associations between potential prognostic indicators and disability at 12 months were carried out in the two LBP subgroups . The final multivariable regression models showed that being non‐employed , having widespread pain , a high level of Chronic Pain Grade , and catastrophising were the strongest prognostic indicators for disability at 12 months in both LBP groups . Fear of pain was significantly associated with disability in chronic LBP . Importantly , beyond baseline disability , the effect size of the other prognostic indicators for poor outcome was rather low . These findings must continue to challenge research ers to identify useful early predictors of outcome in persons with disabling back pain , as screening and targeted treatment approaches are dependent upon prognostic indicators with clinical significance & NA ; The objective of this study is to determine whether depression is an independent risk factor for onset of an episode of troublesome neck and low back pain .  There is growing evidence that pain problems increase the risk of depression . However , the evidence about the role of depression as a risk factor for onset of pain problems is contradictory . This lack of consistency in research findings may be due in part to method ological weaknesses in existing studies , for example , use of an inappropriate study design and inadequate consideration of confounding . A population ‐based r and om sample of adults was surveyed and followed at 6 and 12 months . Individuals at risk of troublesome ( intense and /or disabling ) neck or low back pain are the subjects of this report ( n=790 ) . We used Cox proportional hazards models to measure the time‐varying effect of depressive symptoms on the onset of troublesome neck and low back pain . Our multivariable analysis considered the possible confounding effects of demographic and socio‐economic factors , health status , co‐morbid medical conditions and injuries to the neck or low back . We found an independent and robust relationship between depressive symptoms and onset of an episode of pain . In comparison with the lowest quartile of scores ( the least depressed ) , those in the highest quartile of depression scores had a four‐fold increased risk of troublesome neck and low back pain ( adjusted HRR 3.97 ; 95 % CI 1.81–8.72 ) . Depression is a strong and independent predictor for the onset of an episode of intense and /or disabling neck and low back pain Purpose This r and omized controlled trial had two main aims . The first aim was to investigate the effect of early preventive , psychologically informed , interventions for  pain-related disability .  The second aim was explore whether people who are matched to an intervention specifically targeting their psychological risk profile had better outcomes than people who were not matched to interventions . Methods A total of 105 participants were recruited from their workplace , screened for psychological risk factors and classified as being at risk for long-term pain-related disability . They were subgrouped into one of three groups based on their psychological profile . Three behaviorally oriented psychological interventions were developed to target each of the three risk profiles . Half of the participants were assigned a matched intervention developed to target their specific profile , and half were assigned an unmatched intervention . After treatment , repeated measure ANOVAs and χ2 tests were used to determine if treatments had an effect on primary and secondary outcomes including perceived disability , sick leave , fear and avoidance , pain catastrophizing and distress , and if matched participants had better outcomes than did unmatched . Results Treatments had effects on all outcome variables ( effect sizes d ranging between 0.23 and 0.66 ) , but matched participants did not have better outcomes than unmatched . Conclusions Early , preventive interventions have an impact on a number of outcome variables but it is difficult to realize a matching procedure . More in-depth research of the process of matching is needed This study was a prospect i ve single blind r and omised controlled trial to compare the effects of rehabilitation with emphasis on retraining the vastus medialis ( VMO ) component of the quadriceps femoris muscle and rehabilitation with emphasis on general strengthening of the quadriceps femoris muscles on pain , function and Quality of Life in patients with patellofemoral pain syndrome ( PFPS ) . Patients with PFPS ( n=69 ) were recruited from a hospital orthopaedic clinic and r and omised into three groups : ( 1 ) physiotherapy with emphasis on selectively retraining the VMO ( Selective ) ; ( 2 ) physiotherapy with emphasis on general strengthening of the quadriceps femoris muscles ( General ) ; and ( 3 ) a no-treatment control group ( Control ) . The three groups were then compared before and after an eight-week rehabilitation period . The Selective and General groups demonstrated statistically significant and ' moderate ' to ' large ' effect size reductions in pain when compared to the Control group . Both the Selective and General groups displayed statistically significant and ' moderate ' and ' large ' effect size improvements in subjective function and Quality of Life compared to the Control group . Knee flexion excursion during the stance phase of gait , demonstrated that there were no statistical significant differences and only ' trivial ' to ' small ' effect size differences between the Selective or General groups and the Control group . A large number of PFPS patients can experience significant improvements in pain , function and Quality of Life , at least in the short term , with quadriceps femoris rehabilitation , with or without emphasis on selective activation of the VMO component . Both approaches would seem acceptable for rehabilitating patients with PFPS . It may be appropriate to undertake exercises involving selective activation of the vastus medialis early in the rehabilitation process , however , clinicians should not overly focus on selective activation before progressing rehabilitation , especially in more chronic cases 
    Output:
    
There is limited evidence of mental health and cognitive differences in some individuals with PFP .
Features demonstrating linear correlations with pain and physical function included anxiety/depression , catastrophising , praying and hoping and pain-related fear .
Conclusions Anxiety , depression , catastrophising and fear of movement may be elevated in individuals with PFP and correlate with pain and reduced physical function .