knee osteoarthritis is a disease that causes pain , functional limitation and disability , 
 and its incidence rate is gradually rising with an increase in the elderly population1 , 2 . since knee osteoarthritis causes pain and restricts the mobility of joints , it interferes 
 with walking and activities of daily living3 . an elderly person with knee osteoarthritis is at greater risk of 
 falling down , and it has been reported that about 30% of the elderly population aged 65 and 
 older experience a fall at least once a year4 . the present study aims to analyze factors that affect the quality 
 of life of patients with knee osteoarthritis through an assessment of the patients quality 
 of life . participants for this study were selected from among 135 patients with knee osteoarthritis 
 who were hospitalized at the h hospital in south korea . the inclusion criteria were as 
 follows : patients who have undergone no operations except knee surgery , no functional 
 limitation with nervous system disorders or other diseases , and the ability to understand 
 the purpose of the study and fully participate in it . the exclusion criteria were as 
 follows : patients with other diseases except for knee arthritis , patients that underwent 
 reoperation within one year . the present study was approved by the sahmyook university 
 institutional review board ( syuirb2013 - 021 ) and the objective of the study and its 
 requirements were explained to the subjects , and all participants provided written consent , 
 in accordance with the ethical principles of the declaration of helsinki . in this study , the general characteristics of the participants were recorded and consisted 
 of age , gender , weight , and height . medical characteristics , specifically body mass index , 
 pain in the knee , range of motion in the knee , range of knee contracture , angle of the 
 varus , and quality of life , were evaluated . to measure the pain in the knee the goniometer was used for evaluation of the range of motion in 
 the knee . to measure the angle of the genu varus , we used radiological inspection methods . 
 to measure the quality of life and functional state of the knee before and after knee 
 surgery , we used the knee society function score ( ksfs ) , hospital severity score ( hss ) , 
 short form-36 ( sf-36 ) , and the western ontario and mcmaster universities arthritis index 
 ( womac ) . , the patients rated 
 their pain on a 100  mm horizontal linear scale of 0 to 10 , with a higher score indicating 
 more severe pain5 . during knee flexion and 
 extension , the knee s range of motion the tibiofemoral angle was measured on anterior - posterior x - ray images in a standing 
 position . the function of the knee joint was evaluated based on functional activities using 
 the knee society knee score ( ksfs ) , which encompasses pain , range of motion , stability , 
 flexion contracture and distance of walking , and the knee society function score ( ksfs ) , 
 which includes stair climbing6 . in 
 addition , the hospital severity score ( hss ) was used to evaluate the clinical state of 
 patients with total knee replacement . moreover , the short form 36 ( sf-36 ) health survey was employed to assess the quality of 
 life.its survey consists of a total of eight subcategories of physical function ( pf ) , role 
 physics ( rp ) , bodily pain ( bp ) , general health ( gh ) , vitality ( vt ) , social function ( sf ) , 
 restriction emotion ( re ) and mental health ( mh ) . the score in each subcategory was converted 
 to a scale of 0100 , with a higher score indicating better health2 , 7 . the western 
 ontario and mcmaster universities arthritis index ( womac ) was used along with sf-36 as tools 
 to evaluate knee functions and the patients quality of life8 . the womac comprises a total of 24 subcategories under the key 
 categories of pain , stiffness , and physical functions . scores are on a scale of 0 to 4 , with 
 four being the highest score , and low scores indicate low levels of pain and knee functions . all statistical analyses in this study were performed using the statistical package for the 
 social sciences ( spss ) version 19.0 . the general characteristics of participants are 
 expressed as mean and standard deviation , using the descriptive analysis function in spss . in addition , to evaluate the correlations between sf-36 pcs , sf-36 mcs , functional state and 
 quality of life , a correlation analysis was performed . there were correlations of the sf-36 pcs with age , vas , kss , ksfs , hss , function and rom 
 ( p<0.05 ) . among the subcategories of the sf-36 pcs , vas had high correlations with 
 function while kss had correlations with hss and rom ( p<0.05 ) . in addition , ksfs showed 
 correlations with hss and pain ( p<0.05 ) ( table 
 1table 1.correlation analysis of sf-36 pcssf-36 pcsagesheightsbmivasksspre ltksspre rtksfspre ltksfspre rthsspre lthsspre rtpainfunctionromextentionltromflexionltromextensionrtromflexionrtsf-36 pcs1.000ages0.273 * 1.000heights0.0710.13310.00bmi0.0820.1070.01210.00vas0.543 * 0.1820.0970.0381.000kss lt.0.305*0.363 * 0.1500.0760.248 * 1.000kss rt0.263*0.243 * 0.0440.0500.323 * 0.422 * 1.000ksfs lt0.677*0.276 * 0.217*0.203*0.252 * 0.388 * 0.330 * 1.000ksfs rt0.678*0.263 * 0.1790.1450.289 * 0.414 * 0.344 * 0.915 * 1.000hss lt0.576*0.324 * 0.1340.0320.327 * 0.507 * 0.369 * 0.629 * 0.531 * 1.000hss rt0.560*0.367 * 0.1350.0470.384 * 0.499 * 0.641 * 0.599 * 0.574 * 0.823 * 1.000pain0.648*0.0130.0710.0850.412 * 0.301 * 0.1330.528 * 0.464 * 0.595 * 0.501 * 1.000function0.757*0.1420.0050.0660.660 * 0.285 * 0.236 * 0.491 * 0.449 * 0.551 * 0.482 * 0.696 * 1.000rom extension lt0.1470.267*0.0690.0170.0120.488*0.411*0.224*0.1850.617*0.525*0.0950.0801.000rom flexion lt0.1880.0200.0140.1610.207 * 0.242 * 0.1830.218 * 0.1330.364 * 0.311**0.1390.218*0.1611.000rom extension rt0.0710.270*0.0350.263 * 0.1470.312*0.5610.0310.0070.405*0.534 * 0.0190.1050.660*0.1821.000rom flexion rt0.269 * 0.0090.0940.0030.224 * 0.227 * 0.4010.332 * 0.304 * 0.380 * 0.4850.1280.214*0.279 * 0.699*0.2601.000*p<0.05 ; sf-36 pcs : short form 36- physical component summary ; bmi : body mass 
 index ; kss : knee society score ; ksfs : knee society function score ; hss : hospital 
 special surgery ; rom : range of motion ) . * p<0.05 ; sf-36 pcs : short form 36- physical component summary ; bmi : body mass 
 index ; kss : knee society score ; ksfs : knee society function score ; hss : hospital 
 special surgery ; rom : range of motion there were correlations of the sf-36 mcs with age , bmi , ksfs , function and rom ( p<0.05 ) . 
 among the subcategories of the sf-36 mcs , vas had correlations with the kss , ksfs , hss while 
 kss had correlations with hss , rom , pain and alignment ( p<0.05 ) . in addition , hss showed 
 correlations with pain , function and rom ( p<0.05 ) ( table 2table 2.correaltion of sf-36 mcssfpre mcsagesvasksspre ltksspre rtksfspre ltksfspre rthsspre lthsspre rtpainfunctionromextensionltromflexionltromextensionrtromflexionrtsf pre mcs1.000ages0.0151.000vas0.0160.1821.000kss pre lt0.0890.363*0.248 * 1.000kss pre rt0.0620.243*0.323 * 0.422 * 1.000ksfs pre lt0.320*0.276*0.252 * 0.388 * 0.330 * 1.000ksfs pre rt0.338*0.263*0.289 * 0.414 * 0.344 * 0.915 * 1.000hss pre lt0.1140.324*0.327 * 0.507 * 0.369 * 0.629 * 0.531 * 1.000hss pre rt0.1040.367*0.384 * 0.499 * 0.641 * 0.599 * 0.574 * 0.823 * 1.000pain0.1400.0130.412 * 0.301 * 0.1330.528 * 0.464 * 0.595 * 0.501 * 1.000function0.240*0.1420.6600.285 * 0.236 * 0.491 * 0.449 * 0.551 * 0.482 * 0.696 * 1.000rom extension lt0.1750.267 * 0.0120.488*0.411*0.224*0.1850.617*0.525*0.0950.0801.000rom flexion lt0.0180.0200.2070.242 * 0.1830.218 * 0.1330.364 * 0.311 * 0.1390.218*0.1611.000rom extension rt0.288 * 0.270 * 0.1470.312*0.561*0.0310.0070.405*0.534 * 0.0190.1050.660*0.1821.000rom flexion rt0.0340.0090.2240.227 * 0.401 * 0.332 * 0.304 * 0.380 * 0.485 * 0.1280.214*0.279 * 0.699*0.260 * 1.000*p<0.05 ; sf-36 mcs : short form 36- medical component summary ; bmi : body mass 
 index ; kss : knee society score ; ksfs : knee society function score ; hss : hospital 
 special surgery ; rom : range of motion ) . * p<0.05 ; sf-36 mcs : short form 36- medical component summary ; bmi : body mass 
 index ; kss : knee society score ; ksfs : knee society function score ; hss : hospital 
 special surgery ; rom : range of motion with age , one s overall physical functions decline . in particular , the gait speed and step 
 length decrease due to a smaller range of motion for hip flexion , resulting in an increase 
 in the stance time and a decline in balance while walking . if a patient has knee osteoarthritis , he or she experiences a distinct decline in 
 balance , which causes postural perturbation and greatly affects the quality of life3 . regular exercise is the first and foremost step that elderly people can take to maintain 
 their health . since activities of daily living and leisure are based on full body movement , 
 elderly people , especially people for whom muscle weakness such as arthritis is the 
 underlying cause of illness , should perform regular exercise9 . people in their forties and above have a high incidence of knee osteoarthritis because they 
 generally experience an apparent health decline due to inadequate exercise and individual 
 health management . the pressure on the knee during walking is 0.3 times the body weight 
 whereas the pressure is 2.5 times the body weight during stair ascension , 3.5 times during 
 stair descent and 7 times during squatting10 . given such pressure on the knee , people with severe pain have 
 difficulty in performing efficient movements during the activities of daily living , which 
 may affect the functional assessment scores such as kss , ksfs and hss . the full range of 
 motion is not required to carry out the activities of daily living . about 117 degrees of flexion is required when tying a shoelace or putting on socks , about 
 90 degrees is required to sit on a chair and about 80 degrees is required to climb stairs . however , during knee extension , the full range of motion is needed in order to carry out any 
 activities of daily living without limitation . during the present study , the range of motion 
 appeared to have greater impact on the quality of life . both sf-36 pcs and sf-36 mcs showed 
 high correlations with the range of motion , particularly in subcategories such as kss , hss 
 and ksfs . therefore , management of psychological and mental problems is needed to improve pain in 
 patients with arthritis of the knee . knee osteoarthritis brings about change in the muscle structure and results in a high body 
 mass index and a decrease in both the range of knee flexion and the quadriceps thickness , 
 accompanied by asymmetric weight support and the limitations of gait11 . among patients with knee osteoarthritis , a decrease in the range of knee flexion due to 
 body weight increase has a high correlation with an increase in pain12 . particularly , given the relatively lower effect of 
 rehabilitation programs among patients with bmi higher than 25  kg / m13 , it appears that systematic and professional therapeutic 
 interventions such as aerobic exercises which aim to secure and maintain the range of motion 
 and adequate bmis are needed from the early stages of knee osteoarthritis to enhance the 
 quality of life for knee osteoarthritis patients . the present study has limitations because of a small number of research subjects and future 
 studies should include more research subjects . moreover , the present study explored and 
 identified the muscle strength based on functional scores such as kss . for the purpose of 
 future research , the correlations of the quality of life need to be studied based on an 
 objective assessment of muscle strength . financial disclosure statements have been obtained , and no conflicts of interest have 
 been reported by the author or by any individuals in control of the content of this 
 article . financial disclosure statements have been obtained , and no conflicts of interest have 
 been reported by the author or by any individuals in control of the content of this 
 article .
[ purpose ] the objective of this study is to provide a direction for efficient management 
 of arthritis through the analysis of multiple factors related to the functional state of 
 patients . 
 [ subjects and methods ] the visual analog scale , knee society knee score & 
 function score , hospital for special surgery , short form-36 health survey and western 
 ontario mcmaster universities osteoarthritis index for a total of 135 patients with knee 
 arthritis were determined with a survey . 
 [ results ] there is a significant correlation 
 between age , pain , knee society knee score , hospital for special surgery , knee society 
 function score , and western ontario mcmaster universities osteoarthritis index score . 
 [ conclusion ] it is necessary to improve the factors that affect knee function and quality 
 of life , and a study on knee joint muscle strength is suggested as a follow - up study .