degenerative knee osteoarthritis ( oa ) is a common and painful disease with advancing age 
 and leads to functional disorder1 . patients with degenerative knee oa clinically complain of pain , decreased muscle strength , 
 joint instability , joint stiffness , and proprioceptive deficits , all of which lead to a 
 decrease in or loss of function2 . quadriceps muscle weakness leads to a change in the biomechanics and axis of the knee 
 joint3 , negatively affecting joint 
 mobility , posture , and gait4 . these 
 changes also cause increased dynamic loading in the medial knee joint , resulting in 
 degenerative knee oa5 . changes in the 
 ankle joint especially affect lower extremity alignment during the stance phase and result 
 in overuse of the knee joint6 . in clinical 
 practice , rehabilitation for knee oa typically aims to increase muscle strength and enhance 
 proprioceptive function7 . in particular , 
 due to the contribution of the quadriceps to shock absorption and stability at the knee 
 during gait , previous studies focused more on strengthening knee joint muscles , mainly the 
 quadriceps8 . since quadriceps weakness 
 strongly contributes to disability in knee oa , this may alter local contact stress in a 
 manner detrimental to articular cartilage9 . it may also lead to increased impulse loading , which has been 
 associated with knee pain and may contribute to knee oa9 . anwer et al . indicated that quadriceps exercises can significantly 
 improve knee pain and quadriceps strength10 . in patients with degenerative oa , there is a prominent loss of proprioception compared with 
 healthy people of the same age and gender11 . oa can cause changes that affect not only intracapsular tissues 
 but also periarticular tissues such as ligaments , capsules , tendons , and muscle , leading to 
 proprioceptive deficits both in extremes of joint position and body position12 . a previous study reported proprioception 
 deficits with age progression and reported a greater decrease in patients in knee oa13 . it is clear that in knee oa , 
 proprioception deficits may play a role in oa development and also as contributing risk 
 factors for the progression of oa13 . another study demonstrated the effects of proprioceptive training and strengthening exercise 
 on knee pain , joint function , and proprioception14 . however , studies related to the effects of proprioceptive training 
 and strengthening exercise on joint kinetics in patients with degenerative oa of the knee 
 are rare . therefore , the aim of this study was to determine the effects of proprioceptive 
 training using a balance pad and quadriceps strengthening exercise on foot progression 
 angle , weight - bearing angle , and peak knee adduction moment in patients with degenerative 
 knee oa . the subjects included 60 female patients over the age of 65  years from seoul a senior 
 welfare center . the inclusion criteria were ( 1 ) diagnosis with degenerative oa and had 
 radiologically stage 2 and 3 bilateral knee oa according to the kellgren and lawrence 
 scale15 and ( 2 ) deficits in sensation , 
 circulation , balance , or range of motion , ; lower extremity mmt ; or serious foot problems 
 according to the index of speechley and tinetti . the exclusion criteria were ( 1 ) a history 
 of other neurologic or circulatory diseases or disorders , ( 2 ) any cardiovascular system 
 abnormality , or ( 3 ) any history of knee , hip , or ankle surgery . subjects were randomly 
 allocated to a proprioceptive training group ( ptg ; n=16 ) , quadriceps strengthening group 
 ( qsg ; n=16 ) , or control group ( cg ; n=16 ) . prior 
 to the subjects participation , all procedures were explained , and each subject provided 
 written informed consent to participation . the ptg and qsg therapeutic exercises16 
 were performed for 30  min twice per week for 12 weeks . therapeutic exercise programs were 
 performed one - on - one with a physical therapist . the ankle proprioceptive training program 
 focused on improvement of the proprioception sense of an ankle to correct the joint s 
 position . the ptg performed its exercise program with a torsiomed ( haider ltd , 2000 , 
 germany ) , which and consisted of frontal and sagittal plane exercise . the frontal plane 
 exercise comprised maintenance of balance , lateral tilting , and medial tilting , and the 
 sagittal plane exercise comprised forward tilting and backward tilting . both the frontal and 
 sagittal plane exercises were performed 40 times repeatedly . in the first four weeks , the 
 exercises were performed while standing on both legs with the eyes open and with verbal 
 commands to provide the subjects with visual and auditory feedback . in the next four weeks , 
 they were performed while alternating between standing on the left or right leg . in the last 
 four weeks , the exercises the subjects performed 10 repetitions 
 per set for a total of three sets in the long sitting and supine positions and gradually 
 increased the training intensity every 4 weeks . we offered both groups 3 minutes of rest 
 between sets for recovery from fatigue . on the other hand , the cg only applied a hot pack to 
 both knee for 20 minutes and then tens at 80 to 120  hz for 15 minutes . to evaluate the foot progression angle and weight - bearing ratio , radiographs were taken 
 with a shimadzu 500 x - ray generator on 35.56  91.44 films in a long cassette . the 
 focus - film distance ( fed ) was set at 183 to minimize distortion evaluations . subjects were 
 positioned on a foothold standing with the knees extended , and a radiographer measured the 
 foot progression angle in the same manner before and after the intervention . peak external knee adduction moment was measured using a 3d motion analysis system 
 ( orthostat 6.29 , motion analysis ltd , usa , 2005 ) with eight cameras and two force plates 
 ( piezoelectric force plate , 600  900 , kistler , winterthur , switzerland ) embedded in the 
 center of an 8-m walkway . participants walked in their own low - heeled shoes at a 
 self - selected pace for five trials , and single - leg force platform contacts were recorded . the peak knee adduction moment was normalized to body weight multiplied by height ( force 
 [ n]/body weight  distance [ m]/height [ m ] ) . outcome measures included knee adduction moment 
 magnitude ( knee adduction impulse , loading response [ 1st ] peak and terminal stance [ 2nd ] 
 peak ) . descriptive statistics 
 were used to describe patient characteristics after confirming the data were normally 
 distributed . comparisons of all groups general characteristics were performed using the 
 independent t - test or chi - squared test . pre- and post - intervention data were analyzed using 
 the paired t - test to test within - group differences and one - way anova to test differences 
 among the groups . duncan s post hoc test was used to test the significance of differences 
 between the groups . general subject characteristics are presented in table 
 1table 1.general characteristics of the participantsparametersptg ( n=12)qsg ( n=13)cg ( n=12)age , years71.2 ( 7.0)69.4 ( 3.6)71.2 ( 3.4)height , ( cm)156.0 ( 8.0)153.2 ( 2.2)153.5 ( 1.9)weight , ( kg)65.2 ( 9.1)62.5 ( 5.2)63.7 ( 9.1)kellgren - lawrence grade2.4 ( 0.5)2.6 ( 0.4)2.7 ( 0.5)mean ( sd ) . ptg : proprioceptive training group ; qsg : quadriceps strengthening group ; 
 cg : control group . no significant differences in general characteristics were observed among the 
 ptg , qsg , and cg . differences in pre- and post - intervention values within groups and between 
 groups are summarized in table 2table 2.comparison of foot progression angle , weight- bearing ratio , and knee adduction 
 moment within groups and between groupsparametersvaluesptg ( n=12)qsg ( n=13)cg ( n=12)prepostprepostprepostfoot progression angle ( )loading response9.84 ( 4.86)11.84 ( 3.96)8.02 ( 5.03)7.34 ( 5.90)9.00 ( 7.83)8.51 ( 6.01)terminal stance10.33 ( 4.52)11.11 ( 3.79)10.23 ( 5.78)9.54 ( 6.99)10.21 ( 8.45)9.43 ( 6.21)weight - bearing ratio ( % ) 31.00 ( 10.16)43.67 ( 14.51)35.43 ( 9.60)36.28 ( 9.99)30.14 ( 3.84)29.14 ( 3.72)knee adduction moment ( nm / kg)first peak0.57 ( 0.20)0.44 ( 0.22 ) 0.54 ( 0.15)0.50 ( 0.12)0.53 ( 0.03)0.53 ( 0.12)second peak0.49 ( 0.26)0.43 ( 0.28)0.47 ( 0.14)0.41 ( 0.11)0.44 ( 0.14)0.52 ( 0.06)values are means ( sd ) . * within - group ptg : proprioceptive training group ; qsg : quadriceps 
 strengthening group ; cg : control group . specifically , the ptg showed a significant increase in foot progression angle 
 ( p < 0.05 ) , and the difference was significantly greater than that of the cg . in 
 addition , the ptg showed a significant increase in weight - bearing ratio ( p < 0.05 ) , and 
 the difference was significantly greater than that of the cg . in addition , the first peak 
 knee adduction moment was significantly different between before and after the intervention , 
 and the differences in the ptg were significantly greater than those of the cg ( p < 
 0.05 ) . ptg : proprioceptive training group ; qsg : quadriceps strengthening group ; 
 cg : control group values are means ( sd ) . * within - group difference ( p<0.05 ) . ptg : proprioceptive training group ; qsg : quadriceps 
 strengthening group ; cg : control group this study showed that , in response to 12 weeks of proprioceptive training , participants 
 with degenerative oa exhibited an increase in foot progression angle and weight - bearing 
 ratio and a decrease in first peak knee adduction moment . in this study , there was a significant difference in foot progression angle during the 
 initial stance phase after the intervention . previous studies have reported that the foot 
 progression angle directly affects the medial compartment compressive load in asymptomatic 
 individuals and those with mild to moderate knee oa17 . the present study 
 showed the effect of proprioceptive training , focusing on movement of the foot and ankle 
 joints . during proprioceptive training , subjects controlled the ankle joint in multiple 
 directions to maintain balance on the balance pad , and they repeatedly performed ankle 
 tilting in the frontal and sagittal planes . movement of the ankle in various directions , 
 causing changes in ankle ligament length , facilitates joint stability by creating a reaction 
 to concentric movement19 . in the current 
 study , these results are 
 in accordance with findings showing that changing the foot position improves position sense 
 and joint stability . another interesting result was that the weight - bearing ratio significantly increased in the 
 ptg after the intervention . in a previous study , a weight - bearing ratio of < 50% was 
 defined as genu varus , and a weight - bearing ratio of > 50% was defined as genu 
 valgus21 . of the ptg , it is common to move the weight - bearing line laterally to the center of gravity 
 with a lateral wedge in shoes to correct varus deformities22 . the changes in the weight - bearing ratio in the present study are 
 in accordance with this effect of a lateral wedge . based on this , changes in foot 
 progression angle may result in changes in the weight - bearing ratio by shifting the center 
 of mass and the biomechanical axis to the lateral side . in the present study , the peak knee adduction moment was used to determine the effects of 
 proprioceptive training and quadriceps muscle strengthening exercises . in particular , the 
 external adduction moment of the knee has been demonstrated to be a valid measure for load 
 on the knee medial compartment , a risk factor for disease progression23 , and a useful outcome measure following an 
 intervention22 . the normal predominance 
 of the knee adduction moment throughout the stance phase of gait and its subsequently larger 
 medial knee compartment load relative to the lateral knee compartment load has been 
 suggested to contribute to the markedly greater incidence of advanced oa in the medial knee 
 compartment24 . moreover , in the 
 presence of medial compartment knee oa , articular cartilage degeneration leads to a 
 decreased medial joint space , creating a further shift in the lower limb alignment toward 
 varus25 and an even greater adduction 
 moment about the knee during gait26 . this 
 study demonstrated that participants with degenerative oa exhibited a decrease in first peak 
 knee adduction moment after proprioceptive training . a previous study showed that 
 proprioceptive training increased lower extremity strength and neuromuscular control and 
 reduced peak knee adduction moment in patients with knee oa4 . another study showed that valgus bracing27 and lateral heel wedges28 reduced the magnitude of knee adduction moment during gait . in the 
 present results , the first peak knee adduction moment in the ptg decreased 24% after the 
 intervention . previous studies of valgus bracing27 and wedged insoles28 showed reductions of 13 and 8% , respectively . it has been suggested 
 that every 20% increase in knee adduction moment increases the six - year risk of radiographic 
 progression sixfold29 and that an 8% 
 increase in peak adduction moment increases the risk of developing chronic knee pain four 
 years later23 . therefore , the current 
 study demonstrated that proprioceptive training decreased the adduction moment and delayed 
 disease progression . despite demonstrating the effectiveness of proprioceptive training on leg alignment and 
 knee adduction moment in patients with degenerative oa , this study had some limitations . first , the statistical power was not calculated , and only a small number of subjects were 
 recruited . second , because the participants consisted of only female patients over the age 
 of 65  years , the results of this study can not be generalized to all patients with 
 degenerative oa . therefore , we suggest that further studies include subjects of both genders 
 and a wider age range .
[ purpose ] the purpose of this study was to determine the effect of proprioceptive 
 training on foot progression angle , weight - bearing ratio , and knee adduction moment in 
 patients with degenerative osteoarthritis of the knee . 
 [ subjects ] the subjects were 37 
 patients diagnosed with kellgren - lawrence grade 2 or 3 degenerative knee osteoarthritis . 
 they were randomly allocated to three groups : a proprioceptive training group ( pt group ) , 
 quadriceps strengthening group ( qs group ) , and control group . 
 [ methods ] the study 
 parameters of the three groups were compared before and after a 12-week training period . 
 therapeutic exercises were performed twice per week for 12 weeks . 
 outcomes included the 
 foot progression angle , weight - bearing ratio , and knee adduction moment . 
 [ results ] first , 
 a significant difference in the foot progression angle was observed among the groups , 
 significantly increasing in the ptg compared with the cg . 
 second , a significant difference 
 in the weight - bearing ratio was observed among the groups , significantly increasing in the 
 ptg compared with the cg . 
 third , a significant difference in the first peak knee adduction 
 moment was observed among the groups , significantly decreasing in the ptg compared with 
 the cg . 
 [ conclusion ] the results of the present study indicate that proprioceptive 
 training increased the foot progression angle and weight - bearing ratio and decreased the 
 first peak knee adduction moment . moreover , incorporating proprioceptive training into a 
 physical therapy exercise program could improve functional ability and delay the 
 progression of degenerative osteoarthritis .