a stroke is a disorder that results from a dysfunction in the brain anatomically due to 
 problems in the cerebrovascular blood supply and vessel hemorrhage . depending on the 
 location and seriousness of the damaged in the brain
, stroke patients can have sensory - motor 
 dysfunction , proprioception deficits and hypertonus1 .
the sensory - motor dysfunction in stroke patients includes not only muscle weakness and 
 abnormal muscle tone but also proprioception deficits .
proprioceptiors such as the 
 mechanoreceptor and free nerve ending , are found in the skin , facia , muscles , tendons , joint 
 capsules , and ligaments .
when active or passive movement occurs , receptors transmit the 
 mobility information to the central nervous system2 .
the proprioception provides the angles and angular speed of every 
 joint involved in body position or postural perception and movements .
it plays the largest 
 part in maintaining dynamic joint stability , induces normal movements , and protects joints 
 from external damages3 .
if proprioception 
 is degraded by a stroke , it could also undermine muscle strength , normal muscle tone , 
 posture control , protective reflex ability , and joint motor ability .
clinically , the 
 proprioception level has emerged as an important assessment item used for stroke patient 
 assessment clinically together with treatment procedures4 . in the months following an upper motor neuron ( umn ) lesion in stroke patients , muscle tone 
 increases as a result of changes within the muscle , producing excessive resistance to muscle 
 stretch , which is usually called spasticity .
when a umn lesion interrupts descending motor 
 commands , the lower motor neuron ( lmn ) is affected and becomes temporarily inactive .
this 
 condition is called cerebral shock , depending on the location of the lesion . during nervous 
 system shock
, stretch reflexes can not be elicited , and the muscles are hypotonic ; that is , 
 the muscles have abnormally low tone because facilitation of lmns has been lost due to 
 interruption of descending motor commands by a umn5 .
the most important goal is restoration of somatic sensory function , as 
 this can have a positive effect on abnormal muscle conditions .
the purpose of this study was to compare the proprioception levels of knee joints between 
 the affected and non - affected sides in stroke patients and analyze the correlation of 
 proprioception with muscle strength and spasticity level .
the hypotheses were as follows : 
 the knee joint proprioception in stroke patients will be different in their affected side 
 compared with the non - affected side , and the loss of proprioception will be correlated with 
 muscle strength and spasticity level .
this study examined 31 patients with stroke selected from among the candidates who were 
 receiving physical therapy services at s hospital in daejeon , south korea , and consented to 
 participate in this study .
the criteria for selection of the study subjects were as follows : 
 1 ) patients who agreed to participate in this study experiment , 2 ) patients who could 
 understand and follow a therapist s instructions ( those with an mmse - k score of at least 
 24 ) , 3 ) patients without any orthopedic or neurosurgical history in their ankle joint , hip 
 joint , and lumbar spine , and 4 ) patients with no problems in range of motion in the knee 
 joint .
the research protocol was approved by the research ethics committee for human 
 research of daejeon university , south korea . in this study , to evaluate the joint position sense on both affected and non - affected knee 
 joints of stroke patients , the passive angle reproduction test was utilized , and to evaluate 
 the kinesthesia in both affected and non - affected knee joints of stroke patients , the active 
 angle reproduction test was employed .
the direction of movement during assessment and 
 assessment method were determined by randomly drawing ball marked with flexion and extension 
 ( movement direction ) , passive angle reproduction test , and active angle production test 
 ( assessment method ) , respectively .
participants lay in the side - lying position , flexed slightly their hip joint comfortably , 
 and flexed 70 degrees ( for extension test ) and extended 10 degree ( for flexion test ) their 
 knee joint .
the knee joints were moved by a tester to a target angle 
 without any help .
the flexion angles were set in advance at 50 and 60 degrees6 , 7 . to 
 exclude learning effects during the test
, 60 degrees was used in the active angle 
 reproduction test if 50 degrees was used in the passive angle reproduction test .
the 
 extension test was performed based on 90 degrees of flexion in the knee joints and started 
 from 70 degrees of flexion .
the subjects were instructed to allow a tester to move them 
 passively to a target angle . in the active angle reproduction test , the subjects were 
 instructed to move actively to the target angle .
if 20 degrees was used in the passive angle reproduction test , 30 
 degrees was used in the active angle reproduction test .
to block any visual information from patients , their eyes were covered with a 
 shade during the tests .
a tester caused passive movement by holding the patients ankle and 
 upper part of their knee joint .
the holding time for each target angle was 10 seconds so that the subjects 
 could remember the position . after returning to a starting position
passively or actively , 
 the subjects took a 5-second rest . during the passive angle reproduction test
stop  when they thought their knee joint flexion or extension reached the target 
 angle . during the active angle reproduction test , the subjects moved to the target angles on 
 their own .
the tester marked the results on the measuring board with a sticker and measured the angle 
 with a goniometer .
the measured angles were recorded as negative if they were smaller than 
 the target angle and positive if they were larger than the target angle .
measurements were performed for 3 rounds in total , and 
 the average values were recorded .
the affected - side knee muscle strength of the stroke patients was measured by manual muscle 
 test .
the subjects lay in a side - lying position for the flexion and extension muscle 
 strength test . before the test
, the subjects were examined for any pain and were given a 
 sufficient explanation about the measurement procedures .
the modified ashworth scale ( mas ) was employed in this study to evaluate the spasticity 
 level of the affected - side knee joint .
the mas expresses the degree of spasticity of 
 patients with a damaged central nervous system .
the patients sat 
 comfortably on the treatment stand , and the rater evaluated and recorded the spasticity in 
 the flexion and extension directions .
the larger the number indicating spasticity grade , the 
 more spasticity a patient would have .
the measurement data were statistically processed with pasw statistics for window version 
 18.0 . for the general characteristics of the subjects ,
spearman correlation analysis was employed to 
 analyze the correlation of knee joint proprioception with muscle strength and spasticity in 
 the stroke patients .
the independent t - test was adopted to compare the difference in knee 
 joint proprioception between the affected and non - affected sides .
this study performed a knee joint proprioception test for 31 stroke patients and analyzed 
 the correlation of the proprioception level with muscle strength and spasticity .
table 1table 1.general characteristics of the subjects ( n=31)variables ( unit)subjectsmeansdgender ( male / female)22/9age ( years)51.111.4height ( cm)164.27.3weight ( kg)66.912.1onset ( years)>0.651<onset35<321side of lesion ( left / right)16/15 shows subjects characteristics such as gender , age , height , weight , onset and 
 side of lesion
. comparison of the difference in proprioception levels in the knee joints on 
 the affected and non - affected side in the stroke patients revealed the error angles for 
 joint position sense in the flexion - direction 14.25 degrees on the affected side and 5.33 
 degrees on the non - affected side , representing a significant difference ( p<0.01 ) .
for the 
 extension direction , the error angles were 12.25 degrees on the affected side and 5.15 
 degrees non - affected side , representing a significant difference ( p<0.01 ) . in both the 
 flexion and extension directions ,
the affected sides were found to have a larger error 
 angles in joint position sense than the non - affected sides ( table 2table 2.comparison of proprioception between the affected and non - affected kneetest typedirectionaffected ( n=31)non - affected ( n=31)mean differenceparflexion14.2511.945.334.76 * 8.912.30extension12.259.905.154.99 * 7.101.99aarflexion5.372.363.563.461.810.94extension4.652.623.453.791.201.04par : passive angle reproduction test ( joint position sense ) ; aar : active angle 
 reproduction test ( kinesthesia)mean ( error angle)sd . *
: passive angle reproduction test ( joint position sense ) ; aar : active angle 
 reproduction test ( kinesthesia ) mean ( error angle)sd .
* p<0.01 the correlation of proprioception levels with muscle strength and spasticity in the stroke 
 patients was analyzed .
muscle strength was found to have a negative correlation with the 
 flexors and extensors with respect to joint position sense and the flexors with respect to 
 kinesthesia .
spasticity showed a negative correlation with joint position sense ( p<0.05 ) 
 ( table 3table 3.correlation for coefficients the correlation of 
 proprioception with muscle strength and spasticity in the affected kneeparaarflexionextensionflexionextensionmmtflexor0.836**0.821**0.521*0.218extensor0.847**0.843**0.4110.411mas0.722**0.708**0.5990.600par : passive angle reproduction test ( joint position sense ) ; aar : active angle 
 reproduction test ( kinesthesia ) ; mmt : manual muscle test ; mas : modified ashworth 
 scale .
par : passive angle reproduction test ( joint position sense ) ; aar : active angle 
 reproduction test ( kinesthesia ) ; mmt : manual muscle test ; mas : modified ashworth 
 scale . *
this study examined 31 stroke patients who had been hospitalized or received outpatient 
 treatment by conducting active and passive angle reproduction tests and analyzed the 
 correlation of proprioception with muscle strength and spasticity .
proprioception is a sensory system that plays a key role in maintaining human body 
 stability through motor control by integrating information from peripheral receptors in the 
 central nervous system10 .
stroke patients 
 collect information from peripheral receptors normally , but their central nervous system 
 processes information abnormally , causing errors in original information11 , 12 .
previous studies reported that activation of contractive tissues 
 comprising muscles , rather than non - contractive tissues such as ligaments and joint 
 capsules , was more effective in treating a proprioception deficit13 , 14 .
in addition , 
 active movement rather than passive movement was said to increase proprioception perception 
 ability15 , 16 .
the results of this study showed a significant difference between the affected and 
 non - affected sides in the passive angle reproduction test but not in the active angle 
 reproduction test .
this means that the errors were smaller in the active reproduction test , 
 in which muscle receptors are activated , than in the passive reproduction test , in which 
 muscle receptors are not activated much .
stroke patients have damage in the central nervous system that could cause limb muscle 
 weakness or hypertonus17 .
kim and 
 ahn18 reported that for stroke 
 patients , muscle strength was a significant factor determining movement and that therapy to 
 improve muscle strength improving was more effective than therapy to reduce hypertonus .
they 
 also argued that to restore the sensory - motor system , muscle strength should be reinforced 
 and spasticity should be reduced . in this study ,
examination of the correlation of proprioception with muscle strength and 
 spasticity revealed a negative correlation with muscle strength in the passive angle 
 reproduction test and a positive correlation with spasticity .
this is because weaker muscle 
 and higher spasticity generate larger errors , and this is consistent with previous 
 studies .
this study is limited with respect to the ability to generalize its findings to adult 
 stroke patients in general , as it only examined patients of a single general hospital who 
 met the specific criteria for the study .
another limitation is the small number of subjects , 
 as there were only 31 subjects in this study .
follow - up studies are needed to further study 
 the effects of muscle strength exercise , gait , and balance exercises on proprioception of 
 stroke patients . in summary
, 31 stroke patients were examined through a proprioception test on the affected 
 and non - affected sides of the knee joint .
then their muscle strength and spasticity were 
 analyzed for correlations . in comparison of proprioception between the affected and 
 non - affected knee joints ,
the affected side was found to have a significantly larger error 
 than the non - affected side . in the analysis of the correlation of proprioception with muscle 
 strength and spasticity
, the spasticity levels and joint position sense showed a positive 
 correlation , and muscle strength showed a negative correlation . in conclusion
, this study reported that knee joint proprioception deficits are associated 
 with muscle strength and the spasticity level in stroke patients .
 [ purpose ] the purpose of this study was to investigate the relationship of knee 
 proprioception with muscle strength and spasticity in stroke patients . [ subjects and 
 methods ] 
 the subjects were 31 stroke patients . 
 the subjects received an explanation of the 
 procedures and methods and provided informed consent before the experiment . 
 a measurement 
 board was used to determine the the proprioception deficit of the knee as a proprioception 
 test . 
 the proprioception test consisted of a passive and active angle reproduction test . a 
 manual muscle test and modified ashworth scale were used to evaluate knee muscle strength 
 and spasticity level . 
 the data were analyzed using an independent t - test and spearman 
 correlation . 
 [ results ] the results of this study revealed a significant difference between 
 the affected side and non - affected side in the passive angle reproduction test and a 
 significant difference in the correlation of the proprioception level with muscle strength 
 and spasticity level . 
 [ conclusion ] this study indicates that the knee proprioception level 
 is associated with spasticity and muscle strength in stroke patients . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION