osteoarthritis ( oa ) is a noninflammatory chronic degenerative disease characterized by 
 progressively occurring cartilage destruction , osteophyte formation , and subchondral 
 sclerosis especially in the load - bearing joints . symptomatically , the knee is the most 
 frequently affected joint in osteoarthritis1 , 2 . with the current decrease in mortality of 
 infectious , nutritional , and cardiovascular diseases and increasing lifespan , an increase in weightbearing of the knee joint and weakness in the stabilizing muscles 
 around the joint are important factors accelerating degeneration of the joint . therefore , 
 education about protecting the joint from mechanical trauma , the use of assistive devices , 
 and a strengthening program for the surrounding muscles to increase stability are important 
 in conservative treatment of knee osteoarthritis6 , 
 7 . the extensor effect in the knee and 
 the flexor effect in the hip of the quadriceps muscle play an important role in 
 mobilization . a significant relationship has been shown between quadriceps muscle thickness 
 and strength8,9,10 . however , the degree of 
 atrophy in the quadriceps muscle has not , as yet , been used in oa diagnosis , staging , and 
 evaluation of treatment efficacy or follow - up . the use of ultrasound ( us ) in the diagnosis 
 and follow - up of musculoskeletal system diseases has recently become widespread as a 
 noninvasive , cheap , easy to apply , reliable diagnostic method . us can easily differentiate 
 muscle tissue , bone , fat , and vascular structures and has been reported to be a cheap , 
 practical , valid , and safe choice in valuation of the quadriceps femoris muscle11 . several reliable methods have been 
 defined related to evaluation of the quadriceps femoris muscle mass with us . one of these 
 evaluation methods is measuring of the quadriceps femoris muscle layer thickness by us10,11,12,13,14 . in the present work , the relationship 
 between quadriceps muscle thickness measured by us , clinical parameters , and radiological 
 staging in knee osteoarthritis was investigated . the study included a total of 75 patients ( 51 female , 24 male ) aged 4065 years who were 
 admitted to the physical medicine and rehabilitation polyclinic between february 2013 and 
 june 2013 with complaints of bilateral knee pain and were diagnosed with bilateral knee 
 osteoarthritis according to american college of rheumatology ( acr ) criteria15 . the study was approved by the local 
 ethics committee , and informed consent was obtained from all the study participants . examination and evaluation of all the patients were performed by the same doctor . the age , 
 gender , height ( cm ) , weight ( kg ) , and body mass index ( bmi ,  kg / m ) of the 
 patients were recorded . each patient was questioned about their complaints , history , 
 occupation , and family history . in the physical examination , posture , gait , range of 
 movement of the joint , knee deformities , swelling , increased temperature , instability , 
 crepitation , and patellar shock were evaluated . standing anterior - posterior and lateral knee 
 radiographs were evaluated for each patient using the kellgren - lawrence grading scale16 . for patients that had different grades of 
 oa in the two knees , patients 
 included in their study were chosen according to normal limits for full blood count , fasting 
 blood sugar , liver and kidney function tests , erythrocyte sedimentation rate , c - reactive 
 protein , rheumatoid factors , and full urine tests . patients were excluded from the study if 
 they had a history of knee trauma , surgery , injection in the knee within the previous six 
 months , findings of active synovitis , rheumatoid arthritis , seronegative 
 spodyloartthropathy , gout , pseudogout , osteoporosis , osteomalacia , diabetes mellitus , 
 radiculopathy , coxarthrosis , or any neuromuscular disease , had used any steroid or 
 nonsteroid anti - inflammatory medication within the previous month , or had performed exercise 
 for the quadriceps within the previous month . patients were clinically evaluated using a 
 visual analog scale ( vas ) , the western ontario and mcmaster osteoarthritis index ( womac ) , a 
 50- meter walking test , and a 10-step stair test . the patient scores the pain on a scale of 010 ( 0= no pain , 10= the most 
 severe pain)17 . the womac is a 
 widely - used , valid , and reliable method of evaluating hip and knee oa . the womac oa index 
 consists of 24 questions in 3 sections regarding pain , stiffness , and physical function . all 
 the questions are scored on a scale of 04 ( 0=none , 1=mild , 2=moderate , 3=severe , 4=very 
 severe)18 . in the 50-meter walking test 
 and 10-step stair test , the patients were required to walk a distance of 50 meters if 
 possible and to go up and down 10 stairs if possible , as quickly as possible . the walking 
 and stair tests were repeated three times with rest intervals of at least 5 minutes . measurements of the 
 muscle layer of the quadriceps femoris muscle ( m. vastus intermedius and m. rectus femoris ) 
 were made from specified points as described in previous studies8 , 19 , 20 . the patient was laid supine with their legs in full 
 extension for bilateral assessment of the muscle layer thickness of the m. vastus 
 intermedius and m. rectus femoris from the points ( a ) at the border between the upper and 
 lower two - thirds and point ( b ) at the center of the line between the anterior superior iliac 
 spine and the upper pole of the patella . measurements from points ( a ) and ( b ) were made on 
 both legs , and the mean of those 4 measurements was calculated as the mean muscle layer 
 thickness ( mlt ) . all the ultrasound examinations were performed on a portable siemens acuson 
 antares ultrasound ( siemens , erlangen , germany ) device , equipped with 94  mhz linear array 
 transducers ( siemens acuson antares vfx 9 - 4 ) by a single operator who was oblivious to the 
 randomization and not involved in any further data analysis ( fig . 1.transverse image of the anterior aspect of the m. vastus intermedius and m. rectus femoris . ) . according to the distribution characteristics in the 
 definition and level of the relationship between variables , pearson s or spearman s 
 correlation analysis was used . in the comparison of quantitative data between groups , the 
 mann whitney u test and transverse image of the anterior aspect of the m. vastus intermedius and m. rectus femoris . the mean age and bmi of the patients included in the study were 57.9 5.1  years and 27.6 
 2.2  kg / m respectively . the patient gender ratio ( male : female ) was 
 approximately 2:3 ( table 1table 1 . demographic characteristics of the patients with knee osteoarthritismean  sd ( % ) age ( years)57.9 5.2sex ( female / male)41/19bmi ( kg / m)27.6 2.2duration of disease ( months)76.9  15.2 educationsd ( years)5.4 6.5 employment status n ( % ) employed25 ( 33)official13 ( 17)homemaker27 ( 36 ) others10 ( 14)bmi , body mass index ; sd , standard deviation ) . in examination of the relationship between the thickness of the quadriceps 
 muscle layer and various clinical parameters , a statistically significant negative 
 correlation was determined between patient age and duration of knee oa and quadriceps 
 thickness ( p<0.001 ) . however , no significant correlation was determined between gender , 
 bmi or educational level and quadriceps thickness ( p>0.05 ) ( table 2table 2 . variations in the thickness of the quadriceps muscle layer according to various 
 demographic and clinical characteristics in knee osteoarthritischaracteristics n ( % ) quadricepsthickness ( mm)(mean sd ) age 0.449genderwomen51 ( 68)27.88men24 ( 32)25.15bmi0.449educate years 0.215disease duration0.563oa grade**i15 ( 20)42.6ii18 ( 24)31.0iii27 ( 36)21.6iv15 ( 20)13.0vas- rest0.285vas- active0.342womac - pain0.473womac - stiffness0.496womac - function0.357womac - total0.50250 meters walking time0.47010-step stair time 0.418*p<0.05 ; * * p<0.01 . oa , osteorthritis ; womac , western ontario and mcmaster 
 osteoarthritis index ; vas , visual analog scale ) . when the relationship between the grade of knee oa and quadriceps muscle 
 layer thickness was examined , a statistically significant negative correlation was 
 determined , as quadriceps thickness decreased from grade i to grade iv ( p=0.001 ) ( table 2 ) . however , in the post hoc test ( dunn 
 multiple comparison ) , no significant difference was determined in terms of quadriceps 
 thickness between knee oa grades i and ii , ii and iii , or iii and iv ( p>0.05 ) ( table 2 ) . a statistically significant negative 
 correlation was determined between the quadriceps muscle layer thickness of the patients 
 with knee oa and vas scores at rest and while active ( respectively ; p=0.038 , p=0.012 ) . the 
 womac scores ( pain , stiffness , function , total ) showed a statistically significant negative 
 correlation ( respectively ; p<0.001 , p<0.001 , p=0.009 , p<0.001 ) . there was also a 
 statistically significant negative correlation in the 50-m walking test and the 10-step 
 stair test ( respectively ; p<0.001 , p=0.002 ) . variations in quadriceps muscle layer 
 thickness according to various demographic and clinical characteristics are shown in table 2 . a statistically significant positive 
 correlation was determined between the age of the patients with knee oa and the duration of 
 the disease and the vas , womac , walking test , and stair test scores ( p<0.05 ) . bmi was 
 determined as statistically significantly positively correlated with vas - active ( during 
 patient walking ) , womac - pain and the 10-step stair test scores ( p<0.05 ) ( table 3table 3 . correlation analysis of the demographic and clinical characteristics of the 
 patients with knee osteoarthritisagebmieducateyearsdiseasedurationvas - restvas- activewomac - painwomac- stiffnesswomac - functionwomac - total50 meterswalkingtime10-stepstair timeknee oa grade ( kw)18.09**1.242.9616.43**17.19**18.39**13.90 * 24.24**16.49 * 22.69**12.87 * 11.98*age0.0660.0610.787**0.422 * 0.511**0.516**0.626**0.513**0.628**0.490**0.532**bmi0.453 * 0.1690.2150.305 * 0.337 * 0.2400.1290.2690.2220.303*educate years 0.0650.1750.2440.0510.0960.0640.1090.0280.103disease duration 0.419 * 0.560**0.628**0.617**0.416 * 0.605**0.589**0.555**vas - rest0.699**0.506**0.743**0.323 * 0.528**0.622**0.561**vas - active0.695**0.732**0.536**0.741**0.558**0.573**womac - pain0.713**0.304 * 0.676**0.643**0.634**womac - stiffness0.608**0.839**0.819**0.744**womac - fonction0.892**0.396 * 0.442*womac - total0.634**0.664**50 meters walking time0.864 * * * p<0.05 ; * * p<0.001 . kw , kruskal - wallis test ; oa , osteorthritis ; womac , western 
 ontario and mcmaster osteoarthritis index ; vas , visual analog scale ) . no significant difference was determined between the genders in terms of 
 vas , womac , 50-m walking , and 10-step stair test scores ( table 4table 4 . comparison of the clinical parameters according to genderwomen ( n=51)(mean rank)men ( n=24)(mean rank)vas - rest26.6027.85vas - active28.1324.62womac - pain26.2228.65womac - stiffness25.2930.62womac - function26.4928.09womac - total26.0629.0050 meters walking time ( sn)25.1031.0310-step stair time ( sn)26.7127.62graden ( % ) n ( % ) grade i10 ( 19)5 ( 21)grade ii12 ( 24)6 ( 25)grade iii18 ( 35)9 ( 37)grade iv11 ( 22)4 ( 17)no significant differences between groups at the 0.05 alpha level ) . no significant difference was determined between the quadriceps thickness of 
 the genders when compared in terms of vas , womac , 50-m walking , and 10-step stair test 
 scores ( tables 2 and 4 ) . bmi , body mass index ; sd , standard deviation * p<0.05 ; * * p<0.01 . oa , osteorthritis ; womac , western ontario and mcmaster 
 osteoarthritis index ; vas , visual analog scale * p<0.05 ; * * p<0.001 . kw , kruskal - wallis test ; oa , osteorthritis ; womac , western 
 ontario and mcmaster osteoarthritis index ; vas , visual analog scale no significant differences between groups at the 0.05 alpha level in this study , an evaluation of the relationship between the thickness of the quadriceps 
 muscle layer in patients with knee oa and radiological grade and clinical factors was 
 performed . the results of the study showed a significant negative correlation between 
 quadriceps muscle thickness and age , duration of the disease , grade of knee oa , and vas , 
 womac , 50-m walking test , and 10-step stair test scores . the muscles surrounding joints play 
 an important role in fulfilling the joint function by powering the normal biomechanics of 
 the joint with shock - absorbing effects21 . 
 the quadriceps femoris muscle , as a basic stabilizer of the knee joint , is important for 
 mobilization with extensor function in the knee and flexor function in the hip . according to 
 data from health check - ups , quadriceps muscle strength and thickness in patients with knee 
 oa are significantly reduced and have been reported to be two of the primary risk factors in 
 the development of knee oa10 , 22,23,24,25 . in addition , it 
 has also been determined that quadriceps muscle atrophy and weakness seen from the early 
 stages of knee oa have a significant role in pain and functional loss21 , 26 . our study 
 results confirmed the findings in the literature in terms of the significant negative 
 correlation between quadriceps thickness and pain and functional scores . the most frequently 
 used method to evaluate joint damage and diagnose oa is measurement of the width of the gap 
 in the joint on direct radiographs . when joint degeneration is first determined 
 radiologically and the time of diagnosis of oa , is actually the phase when cartilage damage 
 is considerably advanced at the molecular level27 , 
 28 . it has been reported that methods 
 such as computed tomography ( ct ) , magnetic resonance imaging ( mri ) , and bone scintigraphy 
 can be used in the diagnosis of oa29 . as 
 these diagnostic methods are not practical or economical , they are rarely used in the 
 diagnosis or follow - up of oa . in the current study , we found a significant negative 
 correlation between quadriceps thickness and the grade of knee oa , pain , and function 
 scores . therefore , early determination of knee oa via a quadriceps thickness evaluation can 
 be considered a diagnostic method that will be able to contribute to follow - up of the 
 effectiveness of a treatment program applied for knee age is one of the most important 
 risk factors in the development of oa . this increase in oa incidence at older ages has been reported to be due to reasons such as 
 inadequate muscle function and peripheral neurological response , joint instability 
 associated with increased ligament laxity , reduced anabolic response to growth factors , 
 chondrocyte loss , and thinning of the cartilage plate30 . the results of the current study showed a significant negative 
 correlation between age and quadriceps thickness and a significant positive correlation 
 between age and pain and functional scores . thus , it can be considered that together with 
 ageing , the atrophy in the quadriceps muscle occurring with age contributes to the lower 
 pain and functional scores in knee oa . oa has been reported to be seen more frequently in 
 females than males with more severe pain and function loss . this has been associated with 
 the hormonal changes that occur with age in females resulting in a change in the bone 
 build - destroy balance and failure to develop appropriate coping strategies31 . the majority of the patient group in the 
 current study consisted of females . however , no significant difference was observed in 
 quadriceps thickness between male and female patients in terms of pain and functional 
 scores . it has been known for many years that obesity is a risk factor for oa . high bmi 
 scores of healthy people have been shown to be a significant risk factor for the development 
 of radiographic knee oa in later life32 . this is due to the mechanical loading , particularly on the lower extremities , of 
 obesity33 . it has also been reported 
 that the various adipokines expressed in adipose tissue , such as leptin , adiponectin , 
 resistin , and visfatin , have shown a catabolic effect on articular cartilage34 , 35 . furthermore , sarcopenia has been reported to play an important role 
 in accounting for obesity as a risk factor for the development of oa35 . in the current study , there was a significant positive 
 correlation among bmi and pain scores and the 10-step stair test scores . however , no 
 significant relationship was determined among bmi and radiological grade of knee oa and 
 quadriceps thickness . on this point , in order to better understand the relationship between 
 bmi and knee oa , it is thought that a more appropriate approach may be to evaluate 
 separately whether general sarcopenia was present or not . it has been reported in previous 
 studies that individuals with a low educational level have a higher risk of developing 
 degenerative joint diseases36 . a low 
 level of education is thought to be the reason for inadequacy in commenting on feelings of 
 pain and coping with pain and disability . in addition , a low educational level is thought to 
 engender negative aspects such as a tendency to obesity , incorrect use of joints , a 
 sedentary lifestyle , and not being accustomed to regular exercise . however , in the current 
 study , no significant relationship was determined between educational level and quadriceps 
 thickness and other clinical characteristics of knee oa . as the mean educational level of 
 the patients included in the current study was generally low , it may not have been a 
 sufficient level to demonstrate a relationship between knee oa and education . conflicting 
 results have been reported regarding the relationship between the radiological grade of knee 
 oa , pain , and function loss . reasons have been suggested for this , such as radiographs being 
 taken at different times , interpretation by different researchers , and the use of different 
 methods for grading31 , 33 . in the current study , a significant positive correlation 
 was determined between the grade of knee oa and the pain and functional evaluation scores . in addition , it was significant that as the knee oa grade went from grade i to iv , the 
 thickness of the quadriceps muscle layer showed a significant reduction . when no precautions 
 are taken by patients with knee oa , atrophy occurs with gradual inactivation of the 
 quadriceps muscle . joint stabilization was impaired because of inactivation , and the knee 
 was more easily traumatized . the 
 continuation of this vicious cycle leads to advanced function loss and atrophy in the 
 quadriceps femoris muscle7 . it has been 
 reported that exercise programs applied to prevent quadriceps muscle strength loss and 
 atrophy , have been successful in terms of recovery from pain and recovery of functional 
 parameters26,27,28 . provision of patient 
 with timely information about the factors that may constitute risks for quadriceps atrphy 
 and knee oa is important in terms of preventing physical deficiencies and disruption to 
 social adaptation . preventative measures before the disease occurs , such as maintaining an 
 ideal weight without causing sarcopenia , avoiding incorrect movements that force the joint , 
 prompt treatment of painful conditions that may cause immobilization , and becoming 
 accustomed to regular exercise , will make a positive contribution to knee oa treatment and 
 prognosis . there are some limitations to the current study in that it was cross - sectional , 
 knee oa was only evaluated by plain radiography of the knee , and quadriceps muscle strength 
 was not evaluated . the results of the current study showed that there was a significant 
 correlation between the thickness of the quadriceps muscle layer and the grade of knee oa , 
 pain scores , and functional scores . in this context , the evaluation of quadriceps thickness 
 with us can be considered a practical , economical , and reliable method in the diagnosis and 
 follow - up of knee oa . however , there is a need for further studies with wider patient groups 
 of different demographic and cultural characteristics to evaluate all the factors that may 
 affect the thickness of the quadriceps muscle layer .
[ purpose ] the aim of this study was to investigate the relationship between clinical 
 parameters , radiological staging and evaluated ultrasound results of quadriceps muscle 
 thickness in knee osteoarthritis . [ subjects ] the current study comprised 75 patients ( 51 
 female , 24 male ) with a mean age of 57.95.2  years ( range 4065 years ) and a diagnosis of 
 osteoarthritis in both knees . [ methods ] knee radiographs were evaluated according to the 
 kellgren - lawrence grading system . clinical evaluation performed with the visual analog 
 scale ( vas ) , western ontario and mcmaster osteoarthritis index ( womac ) , the 50-meter 
 walking test , and the 10-step stair test . 
 the thickness of the muscle layer of the 
 quadriceps femoris ( m. vastus intermedius and m. rectus femoris ) was measured with 
 high - resolution real - time ultrasonography . 
 [ results ] the results of this study showed a 
 significant negative correlation between quadriceps thickness and age , duration of 
 disease , stage of knee oa , and vas , womac , 50-m walking test , and 10-step stair test 
 scores . 
 [ conclusion ] the evaluation of quadriceps muscle thickness with ultrasound can be 
 considered a practical and economical method in the diagnosis and follow - up of knee 
 osteoarthritis .