***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: Objective : To assess the clinical relevance of mean and minimum femorotibial joint space narrowing ( JSN ) for predicting future osteoarthritis related surgery in patients with knee osteoarthritis . Methods : 126 subjects with primary knee osteoarthritis were followed prospect ively for a mean eight years .  Minimum and mean joint space width ( JSW ) were assessed from st and ard x rays at baseline and after a follow up of three years . The rate of knee osteoarthritis related surgery was recorded for the following five years . Results : After a mean follow up of eight years , 16 patients ( 12.7 % ) had received osteoarthritis related joint surgery . The areas under the curves ( AUC ) result ing from the receiver operating characteristic curve analyses for predicting osteoarthritis surgery were 0.73 ( p = 0.006 ) for minimum JSN and 0.55 ( p = 0.54 ) for mean JSN . The cut off for minimum JSN maximising sensitivity and specificity for predicting future surgery was a change of 0.7 mm or more in minimum joint space width over a period of three years . However , no meaningful differences were observed for cut off values between 0.5 and 0.8 mm The relative risk ( adjusted for age , body mass index , baseline symptoms , and baseline JSW ) of experiencing osteoarthritis related surgery during the eight year of follow up was 5.15 ( 95 % confidence interval , 1.70 to 15.60 ) ( p = 0.004 ) in patients with a minimum joint space narrowing of 0.7 mm or more during the first three years of the study . Conclusions : A cut off of 0.5 to 0.8 mm in minimum JSN , measured on st and ard x rays , reflects a clinical ly relevant progression in patients with knee osteoarthritis OBJECTIVE The failure to image the patellofemoral joint or the posterior knee compartment when evaluating persons for knee osteoarthritis may result in missed cases . While the skyline view has been recommended due to more reproducible assessment of the patellofemoral joint space , the lateral view may be easier to acquire and provides different information . We evaluated the sensitivity of different combinations of X-ray views ( anteroposterior and lateral ; anteroposterior and skyline ; all three views ) in 377 persons with knee symptoms who had all three views available and had a definite osteophyte on at least one view . RESULTS Of the different views , skylines had to be excluded most often because the image of the patellofemoral joint was technically unsatisfactory . In the remaining knees , adding either a lateral or a skyline view to an anteroposterior view yielded roughly equal and high sensitivity ( 94 - 97 % ) when compared with the gold st and ard of a positive X-ray on any of the three views . CONCLUSION As long as at least an anteroposterior view and one image of the patellofemoral joint is obtained ( either skyline or lateral ) , few cases with radiographic disease will be missed . For clinical or epidemiological studies the lateral view may be easier to acquire with high quality than the skyline view OBJECTIVE Flexion and erect st and ing radiographs were evaluated in the current study to compare their sensitivity in detecting articular cartilage wear . DESIGN Prospect i ve cohort study . SETTING A tertiary care hospital outpatient orthopedic clinic . PATIENTS All patients with osteoarthritis of the knee ages 40 to 75 scheduled for arthroscopic debridement between March 1995 and November 1997 were considered for the current study . INTERVENTION Radiographs were obtained 1 week preoperatively in both the 3-foot st and ing anteroposterior ( AP ) and a 45 degrees posteroanterior ( PA ) flexion weight-bearing projection .  Joint space height was measured with a ruler in millimeters at the narrowest point of each compartment . All radiographs were assessed by two independent observers who were blinded to the arthroscopic findings and clinical symptoms of the subjects . MAIN OUTCOME MEASURES Prediction accuracy of each radiograph for severe Grade IV articular cartilage wear in tibio-femoral compartments . RESULTS One hundred fifty-two patients with a mean ( + /- SD ) age of 60.5+/-8.5 years were enrolled in the study . Fifty-one percent were female . Twelve patients were categorized as having severe lateral compartment articular chondropathy ( Grade IV ) at the time of arthroscopy . The lateral joint space height averaged 1.0+/-1.7 mm SD on the 45 degrees PA radiograph compared with 2.7+/-1.1 mm SD on the 3-foot st and ing AP view . Using a cutoff of 2 mm or less , the 45 degrees PA view was much more sensitive ( 83 % versus 42 % ) at correctly detecting the most severe chondropathy . Forty-one patients were classified with severe Grade IV medial compartment chondropathy at arthroscopy . There was little difference in the average joint space height measured by the 45 degrees PA view ( 1.4+/-1.4 mm SD ) or the 3-foot st and ing AP view ( 1.9+/-1.6 mm SD ) . A number of cutoff measures were evaluated , but no significant advantage could be found for either view in evaluating the medial compartment severity . CONCLUSIONS The bilateral 45 degrees PA is superior for detecting lateral compartment wear but offers no advantage on the medial side . This view should be considered as the screening radiograph of choice in evaluating osteoarthritis of the knee OBJECTIVE To compare quantitative estimates of change in joint space width ( JSW ) with semiquantitative ratings of the progression of joint space narrowing ( JSN ) with respect to sensitivity to change over time . METHODS 431 obese women 45 to 64 years old with unilateral radiographic knee osteoarthritis were r and omised to 30 months ' treatment with doxycycline 100 mg twice daily or placebo . Quantitative estimates of change in JSW in the medial tibiofemoral compartment from fluoroscopically assisted semiflexed AP radiographs were obtained at baseline and 16 and 30 months after r and omisation . Radiographic JSN was rated ( 0 - 3 scale ) in the same images by two readers using a st and ard atlas . Changes in overall severity of knee osteoarthritis were derived from gradings of conventional st and ing AP radiographs at baseline and 30 months , with blinding to treatment group and chronological order of examination . RESULTS Follow up radiographs were obtained from 381 subjects ( 88 % ) at 16 months and from 367 ( 85 % ) at 30 months . The treatment groups did not differ in the frequency of significant loss of JSW by dichotomous criteria ( > or = 0.5 mm , > or = 1.0 mm , > or = 20 % , or > or = 50 % of baseline JSW ) . Progressors and non-progressors , as defined by each of the dichotomous outcomes , differed significantly in mean value for quantitative measurement of change in JSW at 30 months ( p < or = 0.001 ) . CONCLUSIONS Quantitative and semiquantitative indicators of progression of osteoarthritis in fluoroscopically st and ardised radiographs of osteoarthritic knees are highly related , but the effect of doxycycline on articular cartilage thickness was more easily detected with quantitative measurements of change in JSW than with semiquantitative ratings of JSN OBJECTIVE To evaluate the effectiveness of using subchondral bone texture observed on a radiograph taken at baseline to predict progression of knee osteoarthritis ( OA ) over a 3-year period . METHODS A total of 138 participants in the Prediction of Osteoarthritis Progression study were evaluated at baseline and after 3 years . Fractal signature analysis ( FSA ) of the medial subchondral tibial plateau was performed on fixed flexion radiographs of 248 nonreplaced knees  , using a commercially available software tool . OA progression was defined as a change in joint space narrowing ( JSN ) or osteophyte formation of 1 grade according to a st and ardized knee atlas . Statistical analysis of fractal signatures was performed using a new model based on correlating the overall shape of a fractal dimension curve with radius . RESULTS Fractal signature of the medial tibial plateau at baseline was predictive of medial knee JSN progression ( area under the curve [ AUC ] 0.75 , of a receiver operating characteristic curve ) but was not predictive of osteophyte formation or progression of JSN in the lateral compartment . Traditional covariates ( age , sex , body mass index , knee pain ) , general bone mineral content , and joint space width at baseline were no more effective than r and om variables for predicting OA progression ( AUC 0.52 - 0.58 ) . The predictive model with maximum effectiveness combined fractal signature at baseline , knee alignment , traditional covariates , and bone mineral content ( AUC 0.79 ) . CONCLUSION We identified a prognostic marker of OA that is readily extracted from a plain radiograph using FSA . Although the method needs to be vali date d in a second cohort , our results indicate that the global shape approach to analyzing these data is a potentially efficient means of identifying individuals at risk of knee OA progression Preoperatively predicting chondral damage is important . Weightbearing radiographs , including the st and ing antero- posterior and 45 ° flexion posteroanterior views traditionally have been used for this purpose . We wanted to determine if one radiograph had superior sensitivity or specificity in detecting arthroscopically confirmed Grade II chondromalacia ( mild arthritis ) . A st and ard prospect i ve st and ing radio- graphic protocol was design ed for all patients who presented to a sports medicine center with knee complaints . Patients who had subsequent arthroscopic surgery  had their radio- graphs measured in a blinded manner for articular cartilage intervals in millimeters to detect joint-space narrowing . Intraarticular chondral damage was correlated with the radio- graphic findings . Three hundred forty-nine of a possible 411 ( 87 % ) patients during a 2-year period had both radiographs and subsequent  arthroscopic grading of chondromalacia . This has been the largest study that correlated arthroscopic chondromalacia grade s with two commonly preferred weightbearing radiograph projections . Despite specificities greater than 90 % , the sensitivity was extremely low and neither st and ing radiograph was superior . Neither radiograph was useful in detecting Grade II chondral damage . Level of Evidence : Diagnostic study , Level I-1 ( testing of previously developed diagnostic criteria in series of consecutive patients -with universally applied reference “ gold ” st and ard ) . See the Guidelines for Authors for a complete description of levels of evidence We proposed to establish a system of assessing severity of chondropathy taking into account localization , size , and depth of cartilage lesions . The design of the study was prospect i ve and multicenter . The subjects were 755 patients who had undergone arthroscopy of the knee .  Criteria for assessment of severity of chondropathy were as follows : ( a ) Physician 's overall assessment using a 100-mm-long Visual Analogue Scale , and ( b ) size , grade , and localization of cartilage lesions recorded on a diagram . We used multivariate parametric and nonparametric analyses . The analyses result ed in two systems of assessing severity of chondropathy : SFA scoring for the three compartments of the knee , which is a continuous variable , and SFA grading , which is a semiquantitative variable . These systems seem to be of clinical relevance . However , more studies are required to further vali date them and their capacity to detect changes in severity of chondropathy Twenty-seven patients with chronic knee pain were examined prospect ively using conventional radiography , radionuclide angiography , planar bone scintigraphy , and single-photon emission computed tomographic ( SPECT ) bone scintigraphy . When the results of subsequent arthroscopic examination of all three compartments of the knee were correlated with those of the noninvasive methods , SPECT bone scintigraphy was found to be most sensitive for evaluating the extent of osteoarthritis . Differences in detection sensitivity for articular cartilage damage and synovitis were greatest in the patellofemoral compartment . The frequency with which hyperemia was present in association with cartilage damage and synovitis indicates that osteoarthritis of the knee is capable of producing hyperemia and further implies that increased perfusion can not be used to distinguish with confidence between osteoarthritis and septic processes involving the knee . SPECT ( 1.00 ) and planar ( 0.91 ) bone scintigraphy were highly sensitive indicators of torn menisci in a subgroup of 14 patients , each having a prearthroscopic clinical diagnosis of a torn meniscus . This result suggests that for patients with chronic knee pain and clinical suggestion of a torn meniscus , bone scintigraphy has significant potential as a high-sensitivity , prearthroscopic screening examination OBJECTIVE To evaluate progression of joint space narrowing in radiographs of osteoarthritic ( OA ) knees imaged in both the st and ing anteroposterior ( AP ) and the Lyon schuss positions , using alternative methods to measure joint space width ( JSW ) . METHODS St and ing AP ( extended view ) and  Lyon schuss ( posteroanterior [ PA ] view , with 20 - 30 degrees of flexion ) radiographic images of 58 OA knees were obtained twice ( at baseline and 2 years later ) . With both methods , 
    Output:
    
The 45 ° flexion PA view showed a higher sensitivity than the st and ing AP view for detecting severe arthritis involving either the medial or lateral tibiofemoral compartment .
There was no difference in the specificities for the 2 views .
The direct comparison of the Kellgren-Lawrence and the JSN radiographic grading systems found no clinical difference between the 2 systems regarding the sensitivities , although the specificity was greater for the JSN system .
However , as an inexpensive screening tool , the 45 ° flexion PA view is more sensitive than the st and ing AP view to detect severe tibiofemoral osteoarthritis .
When evaluating the radiograph for severe osteoarthritis using either the Kellgren-Lawrence or JSN grading system , there is no clinical difference in the sensitivity between the 2 methods ; however , the JSN may be more specific for ruling in severe osteoarthritis in the medial compartment .