***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 Bone marrow lesions ( BMLs ) , common osteoarthritis-related magnetic resonance imaging findings , are associated with osteoarthritis progression and pain . However , there are no articles describing the use of 3-dimensional quantitative assessment s to explore the longitudinal relationship between BMLs and hyaline cartilage loss . The purpose of this study was to assess the cross-sectional and longitudinal descriptive characteristics of BMLs with a simple measurement of approximate BML volume , and describe the cross-sectional and longitudinal relationships between BML size and the extent of hyaline cartilage damage . Methods 107 participants with baseline and 24-month follow-up magnetic resonance images from a clinical trial were included with symptomatic knee osteoarthritis . An ' index ' compartment was identified for each knee defined as the tibiofemoral compartment with greater disease severity . Subsequently , each knee was evaluated in four regions : index femur , index tibia , non-index femur , and non-index tibia . Approximate BML volume , the product of three linear measurements , was calculated for each BML within a region . Cartilage parameters in the index tibia and femur were measured based on manual segmentation . Results BML volume changes by region were : index femur ( median [ 95 % confidence interval of the median ] ) 0.1 cm3 ( -0.5 to 0.9 cm3 ) , index tibia 0.5 cm3 ( -0.3 to 1.7 cm3 ) , non-index femur 0.4 cm3 ( -0.2 to 1.6 cm3 ) , and non-index tibia 0.2 cm3 ( -0.1 to 1.2 cm3 ) . Among 44 knees with full thickness cartilage loss , baseline tibia BML volume correlated with baseline tibia full thickness cartilage lesion area ( r = 0.63 , p < 0.002 ) and baseline femur BML volume with longitudinal change in femoral full thickness cartilage lesion area ( r = 0.48 p < 0.002 ) . Conclusions Many regions had no or small longitudinal changes in approximate BML volume but some knees experienced large changes . Baseline BML size was associated to longitudinal changes in area of full thickness cartilage loss It has been suggested that bone marrow edema-like ( BME ) lesions in the knee are associated with progression of osteoarthritis ( OA ) . The purpose of our study in patients with OA was to evaluate prospect ively changes of BME lesions over 2 years and their relationship with clinical features . Magnetic resonance ( MR ) images of the knee were obtained from 182 patients ( 20 % male ; aged 43–76 years ; mean age 59 years ) who had been diagnosed with familial symptomatic OA at multiple joint sites . MR images were made at baseline and at 2 years follow-up .  BME  lesions in 2 years were associated with clinical features assessed by Western Ontario and McMaster Universities Osteoarthritis ( WOMAC ) scores . A total of 327  BME lesions were recorded . Total size of BME lesions changed in 90 patients ( 66 % ) . Size of individual lesions changed in 147 foci ( 45 % ) : new lesions appeared in 69 ( 21 % ) , existing lesions disappeared in 32 ( 10 % ) , increased in size in 26 ( 8 % ) and decreased in size in 20 ( 6 % ) lesions . Increase or decrease of BME lesions , over a 2-year time period , was not associated with severity of WOMAC scores . BME lesions fluctuated in the majority of patients with OA over a 2-year time period . These changes were not associated with severity of WOMAC scores at the study end point Introduction There are conflicting data on the natural history and clinical significance of bone marrow lesions ( BMLs ) . The aims of this study were to describe the natural history of MRI-detected BMLs at the knee using a quantitative measure and examine the association of BMLs with pain , function and stiffness scores , and total knee replacement ( TKR ) surgery . Methods A total of 395 older males and females were r and omly selected from the general population ( mean age 63 years , range 52 to 79 ) and measured at baseline and approximately 2.7 years later .  BMLs  were determined using T2-weighted fat saturation MRI by measuring the maximum area of the lesion . Reproducibility was excellent ( intraclass correlation coefficient ( ICC ) : 0.97 ) . Pain , function , and stiffness were assessed by Western Ontario and McMaster Universities Osteoarthritis ( WOMAC ) scores . X-ray was used to assess radiographic osteoarthritis ( ROA ) at baseline . Results At baseline , 43 % ( n = 168/395 ) had a BML . Of these 25 % decreased in size and 24 % increased . Of the remaining sample ( n = 227 ) , 7 % developed a new BML . In a multivariable model , a change in BML size was associated with a change in pain and function scores ( β = 1.13 to 2.55 per 1 SD increase , all P < 0.05 ) , only in those participants without ROA . Lastly , baseline BML severity predicted TKR surgery ( odds ratio ( OR ) 2.10/unit , P = 0.019 ) . Conclusions In a population based sample , BMLs ( assessed by measuring maximal area ) were not static , with similar proportions both worsening and improving . A change in BML size was associated with changes in pain in those without established ROA . This finding suggests that fluctuating knee pain may be attributable to BMLs in those participants with early stage disease . Baseline BMLs also predicted TKR surgery . These findings suggest therapeutic interventions aim ed at altering the natural history of BMLs should be considered Introduction To examine the relationship between development or resolution of bone marrow lesions ( BMLs ) and knee cartilage properties in a 2 year prospect i ve study of asymptomatic middle-aged adults . Methods 271 adults recruited from the Melbourne Collaborative Cohort Study , underwent a magnetic resonance imaging scan ( MRI ) of their dominant knee at baseline and again approximately 2 years later . Cartilage volume , cartilage defects and BMLs were determined at both time points . Results Among 234 subjects free of BMLs at baseline , 33 developed BMLs over 2 years . The incidence of BMLs was associated with progression of tibiofemoral cartilage defects ( OR 2.63 ( 95 % CI 0.93 , 7.44 ) , P = 0.07 for medial compartment ; OR 3.13 ( 95 % CI 1.01 , 9.68 ) , P = 0.048 for lateral compartment ) . Among 37 subjects with BMLs at baseline , 17 resolved . Resolution of BMLs was associated with reduced annual loss of medial tibial cartilage volume ( regression coefficient -35.9 ( 95%CI -65 , -6.82 ) , P = 0.02 ) and a trend for reduced progression of medial tibiofemoral cartilage defects ( OR 0.2 ( 95 % CI 0.04 , 1.09 ) , P = 0.06 ) . Conclusions In this cohort study of asymptomatic middle-aged adults the development of new BMLs was associated with progressive knee cartilage pathology while resolution of BMLs prevalent at baseline was associated with reduced progression of cartilage pathology . Further work examining the relationship between changes and BML and cartilage may provide another important target for the prevention of knee osteoarthritis OBJECTIVE To describe the frequency of bone marrow lesions ( BMLs ) detected by magnetic resonance imaging ( MRI ) , and to examine the association of BMLs with knee pain severity in community residents in Korea . METHODS Participants were r and omly chosen from the population -based Hallym Aging Study , irrespective of whether they had knee osteoarthritis ( OA ) or pain . Demographic and knee pain data were obtained by question naire . Radiographic evaluations consisted of weight-bearing knee anteroposterior radiographs and 1.5-T MRI scans . MRI was performed in the dominant knees of subjects without knee pain and in the more symptomatic knees of subjects with knee pain . BMLs were grade d according to the whole-organ MRI score . RESULTS The mean age of the 358 study subjects was 71.8 years , and 34.5 % of subjects had radiographically detected knee OA . The prevalences of BMLs and large BMLs in the tibiofemoral compartments were 80.3 % and 40.4 % , respectively . After adjusting for age , sex , and body mass index , total and medial compartment BML scores were significantly associated with the presence of knee pain , and the association was stronger as the summary score for BML increased . In proportional regression analysis , knee pain severity increased with BML severity in any compartment and in the medial compartment . CONCLUSION BMLs detected by MRI were highly prevalent in this elderly Asian population . BMLs were significantly linked to knee pain , and BML severity correlated with knee pain severity . BMLs may be important surrogate targets for monitoring pain and structure modification in OA therapeutics OBJECTIVE To describe the association between chondral defects , bone marrow lesions , knee and hip radiographic osteoarthritis ( OA ) , and knee pain . METHODS Knee pain was assessed by the Western Ontario and McMaster Universities Osteoarthritis Index . T1- and T2-weighted fat saturation magnetic resonance imaging was performed on the right knee to assess chondral defects and subchondral bone marrow lesions . Radiography was performed on the right knee and hip and scored for radiographic OA . Body mass index ( BMI ) and knee extension strength were measured . RESULTS A total of 500 r and omly selected men and women participated . The prevalence of knee pain was 48 % . In multivariable analysis , prevalent knee pain was significantly associated with medial tibial chondral defects ( odds ratio [ OR ] 2.32 , 95 % confidence interval [ 95 % CI ] 1.02 - 5.28 for grade 3 versus grade 2 or less ; OR 4.93 , 95 % CI 1.07 - 22.7 for grade 4 versus grade 2 or less ) , bone marrow lesions ( OR 1.44 , 95 % CI 1.04 - 2.00 per compartment ) , and hip joint space narrowing ( OR 1.36 , 95 % CI 1.07 - 1.73 per unit ) , as well as greater BMI and lower knee extension strength . It was not significantly associated with radiographic knee OA . These variables were also associated with more severe knee pain . In addition , there was a dose response association between knee pain and number of sites having grade 3 or 4 chondral defects ( OR 1.39 , 95 % CI 1.12 - 1.73 per site ) , with all subjects having knee pain if all compartments of the knee had these defects . CONCLUSION Knee pain in older adults is independently associated with both full and non-full-thickness medial tibial chondral defects , bone marrow lesions , greater BMI , and lower knee extension strength , but is not associated with radiographic knee OA . The association between radiographic hip OA and knee pain indicates that referred pain from the hip needs to be considered in unexplained knee pain Context Bone marrow edema on magnetic resonance imaging ( MRI )  correlates with pain in patients with knee osteoarthritis , but its association with progression of joint changes is unknown . Contribution Among 223 patients with knee osteoarthritis , bone marrow edema on MRI  was associated with radiographic progression in the same compartment over the following 15 to 30 months after adjustment for age , sex , body mass index , and limb malalignment ( another predictor of progression ) . Caution s While this study shows that bone marrow edema is associated with the progression of knee osteoarthritis , we do not know whether it is causal or an epiphenomenon . These findings do not define a role for MRI in the routine evaluation of knee osteoarthritis . The Editors Osteoarthritis , the most common form of arthritis , is the leading cause of mobility-related disability in elderly persons ( 1 ) . With the aging of the population , the prevalence of osteoarthritis is increasing . Loss of hyaline articular cartilage is a central pathologic event in osteoarthritis , but the pathogenesis of cartilage loss is poorly understood . Specifically , there is a paucity of information about what factors identify joints at high risk for progression . Identification of such factors might permit better underst and ing of the disease process . While cartilage loss is a major pathologic feature of osteoarthritis , abnormal bone has been documented as another important element . Bone scan studies of persons with osteoarthritis have reported late-phase uptake of tracer in subchondral bone , signifying accelerated bone turnover . This increase in tracer has been associated with joint pain ( 2 ) and with a markedly increased risk for radiographic progression in osteoarthritis of the knee ( 3 ) and h and ( 4 ) . The study in knees , however , was limited by the use of out date d radiographic techniques ( 5 ) . Increased uptake on bone scan has a parallel finding on magnetic resonance imaging ( MRI ) :  bone marrow edema ( 6 , 7 ) . Bone marrow edema is indicated by focally increased signal in the marrow on fat-suppress 
    Output:
    
The occurrence of BML is an important index for severe degenerative pathologies in the knee .
It appears that MRT symptoms predict the progression of the disease .