***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: 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 A prospect i ve study of 390 infantry recruits revealed that the medial tibial intercondylar distance and that the isometric strength of the quadriceps , tested at 85 degrees of flexion of the knee , had a statistically significant correlation with the incidence of patellofemoral pain caused by overactivity . Increased  medial tibial intercondylar distance and increased strength of the quadriceps were therefore deemed to be risk factors for this syndrome Background Patellofemoral pain syndrome is one of the most common chronic knee injuries ; however , little research has been done to determine the risk factors for this injury . Hypothesis Altered lower extremity kinematics and kinetics , decreased strength , and altered postural measurements will be risk factors . Study Design Cohort study ( prognosis ) ; Level of evidence , 2 . Methods A total of 1597 participants were enrolled in this investigation and prospect ively followed from the date of their enrollment ( July 2005 , July 2006 , or July 2007 ) through January 2008 , a maximum of 2.5 years of follow-up . Each participant underwent baseline data collection during their pre-freshman summer at the United States Naval Academy . Baseline data collection included 3-dimensional motion analysis during a jump-l and ing task , 6 lower extremity isometric strength tests , and postural alignment measurements ( navicular drop and Q angle ) . Results Risk factors for the development of patellofemoral pain syndrome included decreased knee flexion angle , decreased vertical ground-reaction force , and increased hip internal rotation angle during the jump-l and ing task . Additionally , decreased quadriceps and hamstring strength , increased hip external rotator strength , and increased navicular drop were risk factors for the development of patellofemoral pain syndrome . Conclusion Multiple modifiable risk factors for patellofemoral pain syndrome pain have been identified in this investigation . To decrease the incidence of this chronic injury , the risk factors for patellofemoral pain syndrome need to be targeted in injury prevention programs . Clinical Relevance Prevention programs should focus on increasing strength of the lower extremity musculature along with instructing proper mechanics during dynamic movements to decrease the incidence of patellofemoral pain syndrome Objective : To prospect ively determine gait-related risk factors for patellofemoral pain .  Design : A prospect i ve cohort study . Setting : Male and female recruits of the Belgian Royal Military Academy during a 6-week basic military training period . Participants : Eighty-four officer cadets ( 65 men , 19 women ) , who entered the Military Academy and were without a history of any knee or lower-leg complaints , participated in the study . Interventions : Before the start of the 6-week basic military training period ,  plantar pressure measurements during walking were performed . During the basic military training period , patellofemoral complaints were diagnosed and registered by a sports medicine physician . Main Outcome Measurements : Plantar pressure measurements during walking were performed using a footscan pressure plate ( RsScan International ) . Results : During the 6-week training period , 36 subjects developed patellofemoral pain  ( 25 male and 11 female ) . Logistic regression analysis revealed that subjects who developed patellofemoral pain had a significantly more laterally directed pressure distribution at initial contact of the foot , a significantly shorter time to maximal pressure on the fourth metatarsal , and a significantly slower maximal velocity of the change in lateromedial direction of the center of pressure during the forefoot contact phase . Conclusions : Our findings suggest that the feet of the persons who developed anterior knee pain have a heel strike in a less pronated position and roll over more on the lateral side compared with the control group . The results of this study can be considered valuable in identifying persons at risk for patellofemoral pain Background Inappropriate control of the vastus medialis oblique and vastus lateralis muscles by the central nervous system can contribute to maltracking of the patella . Hypothesis The activation timing and amplitude of the vastus medialis oblique and vastus lateralis muscles will be different between normal subjects and patients with patellofemoral pain . Study Design Controlled laboratory study . Methods Subjects with patellofemoral pain and asymptomatic control subjects performed maximum voluntary knee extension contractions initiated from a flexed and an extended position . The activation timing and amplitude of the vastus lateralis and vastus medialis oblique muscles were quantified from the recorded electromyographic signals . Results There were no between-group differences in activation timing . The activation amplitude of the vastus medialis oblique and vastus lateralis muscles of the patellofemoral pain subjects was altered to the greatest extent during eccentric contractions and differed significantly from that of control subjects . Conclusions The activation amplitudes of the vastus medialis oblique and vastus lateralis muscles of subjects with patellofemoral pain are consistent with a laterally tracking patella during eccentric contractions . Clinical Relevance The findings suggest the clinical importance of determining whether altered activation patterns are sensitive to rehabilitation , and , if so , if subjective reports of knee joint pain and function parallel changes in the activation patterns as a result of rehabilitation PURPOSE There is emerging evidence that foot orthoses are effective in the management of  patellofemoral pain syndrome ( PFPS ) . However , the identification of those most likely to benefit from foot orthoses has not been adequately explored . The aim of this study was to develop a preliminary clinical prediction rule to help identify individuals with PFPS who are most likely to benefit from foot orthoses . METHODS A total of 60 individuals with PFPS were issued with noncustomized prefabricated foot orthoses containing built-in arch supports and 4 ° rear foot varus wedging . Patient-reported level of improvement was documented at 12 wk . Potential baseline predictor variables of interest included patient demographics , pain characteristics , footwear motion control properties , foot and ankle characteristics , and functional performance measures . RESULTS Fourteen ( 25 % ) participants reported marked improvement at 12 wk . The number of participants with marked improvement increased to 78 % if three of the following four criteria were met : footwear motion control properties score of < 5.0 ( indicative of less supportive footwear ) , usual pain < 22.0 mm , ankle dorsiflexion range of motion ( knee flexed ) < 41 ° , and reduced single-leg squat pain when wearing the orthoses . CONCLUSIONS Individuals with PFPS who wear less supportive footwear , report lower levels of pain , exhibit less ankle dorsiflexion range of motion , and report an immediate reduction in pain with foot orthoses when performing a single-leg squat are more likely to benefit from foot orthoses Objective Patellar malalignment is a major cause of patellofemoral pain syndrome ( PFPS ) , but the relationship between clinical symptoms and changes in patellar position and knee muscle strength has not been confirmed . This study examined the effect of weight training on hip and knee muscle strength , patellofemoral joint contact area , and patellar tilt on subjects with and without PFPS , hoping to develop an optimal rehabilitation protocol for subjects with PFPS . Design The study uses a prospect i ve independent group comparison . Fifteen subjects with and without PFPS were assessed for knee strength , patellofemoral joint contact area , and patellar tilt angle using magnetic resonance imaging . The subjects with PFPS were also examined and given a numeric pain rating score and a Kujala patellofemoral score . The subjects performed lower-limb weight training 3 times/wk for 8 wks , and the outcomes were assessed both before and after training . Results Subjects with PFPS have increased their patellofemoral joint contact area after weight training ( P < 0.001 ) . No statistical significant change was found on the patellar tilt angle . The isometric and isokinetic knee strength in subjects with and without PFPS have increased after weight training ( P value increased from 0.007 to 0.05 ) . Both numeric pain rating and Kujala patellofemoral score in the PFPS group improved after training ( P < 0.001 ) . Conclusions Weight-training exercise increased knee muscle strength and the patellofemoral joint contact area , which could reduce mechanical stress in the joint , improving pain and function in subjects with PFPS Objective : To determine prospect ively gait-related intrinsic risk factors for patellofemoral pain ( PFP ) in a population of novice recreational runners . Design : Prospect i ve cohort study . Participants : 102 novice recreational runners ( 89 women ) with no history of knee or lower leg complaints . Interventions : The st and ing foot posture of the subjects was examined and plantar pressure measurements during running were collected . The subjects then participated in a 10-week “ start to run ” programme . During this period all sports injuries were registered by a sports medicine physician . Main outcome measurements : The relationship between the st and ing foot posture and PFP was investigated and gait-related intrinsic risk factors for PFP were determined . Results : The 17 runners who developed PFP exerted a significantly higher vertical peak force underneath the lateral heel and metatarsals 2 and 3 . Logistic regression analysis showed that a significantly higher vertical peak force underneath the second metatarsal and shorter time to the vertical peak force underneath the lateral heel were predictors for PFP . No significant evidence was found for an association between an excessively pronated or supinated foot posture and the development of PFP . Conclusions : The findings suggest that an excessive impact shock during heel strike and at the propulsion phase of running may contribute to an increased risk of developing PFP . The hypothesis that persons at risk for PFP show an altered static foot posture in comparison with non-afflicted persons is not supported by the results of this study Background : The prevalence of adolescent knee pain is 33 % , and patellofemoral pain ( PFP ) is the most common diagnosis with a nontraumatic onset . The 2-year prognosis of adolescent PFP compared with other types of knee pain is unknown . Purpose : To investigate the 2-year prognosis of knee pain among adolescents with and without a diagnosis of PFP . Study Design : Cohort study ; Level of evidence , 2 . Methods : In 2011 , a cohort of 2200 adolescents aged 15 to 19 years answered an online question naire on musculoskeletal pain .  Of these , 504 reported knee pain , and 153 of these were clinical ly diagnosed with PFP . After 2 years , the 504 adolescents , as well as 252 r and omly selected adolescents who did not report knee pain in 2011 , were contacted again . Primary outcome at follow-up was the proportion of adolescents with knee pain during the last week prior to follow-up . Results : Overall , 55.9 % ( 95 % CI , 50.8%-60.9 % ) of those reporting knee pain at baseline also reported pain 2 years later . Adolescents diagnosed with PFP had a 1.26 ( 95 % CI , 1.05 - 1.50 ) higher relative risk ( RR ) of knee pain at follow-up compared with other types of knee pain . Adolescents with PFP were significantly more likely to reduce or stop sports participation compared with adolescents with other types of knee pain . Of those without knee pain at baseline , 12.8 % ( 95 % CI , 8.4%-17.2 % ) reported knee pain at follow-up in 2013 . Adolescents with knee pain at baseline had a 4.51 ( 95 % CI , 3.15 - 6.45 ) higher RR of knee pain at follow-up compared with adolescents without knee pain at baseline . Conclusion : Knee pain during adolescence , and PFP in particular , is in most cases present after 2 years and thus may not be self-limiting . 
    Output:
    
No significant link between BMI and intervention outcomes in adults with PFP was identified .
Conclusions Higher BMI is present in PFP and PFOA , but not in adolescents with PFP .