the knee joint is the largest and most complicated joint which acts as a major weight 
 bearing joint involved in walking , stepping , and running .
normally , the knee joint supports 
 46 times the body weight during gait and decreases energy consumption by reducing vertical 
 and lateral movements from the body center1 , 2 .
however , tissue injury can occur in the 
 knee joint if excess range of motion or abnormal movement is made3 . the femoral bone connected to the tibia plays an important 
 role in the longitudinal axis of the lower limb which is related to the tibial rotation 
 angle4 .
furthermore , disabled tibial 
 rotation induces osteoarthritis and musculoskeletal imbalance following the change of 
 compression and rotation force with abnormal femoral movement5 , 6 .
the hamstring muscle consists of the semimembranosus and semitendinosus muscles in the 
 medial part and the short and long head of the biceps femoris muscle in the lateral part 
 that have a function in a medial and lateral tibial rotation , respectively7 .
also , the hamstring muscle contributes to 
 the stability and sagittal and transverse plane movement of the knee8 . while changing the length of the muscle fibers and tendons 
 has an effect on the hamstring strength , abnormal gait and exercise
can also cause pain or 
 muscle imbalance , which in turn can change body posture .
the anatomical cross - sectional area 
 and the thickness of the muscle are well known parameters of functional capacity measurement 
 that have an effect during resistance exercises9 . in a previous study
it was shown that there is a strong 
 relationship between the hamstring thickness measured using ultrasound imaging and the 
 cross - section area at the 5070% region of thigh length examined using magnetic resonance 
 imaging ( mri)10 .
thus , the study of leg 
 muscle contraction changes using ultrasound imaging has a beneficial clinical meaning .
several studies indicated that muscle imbalance between the medial and lateral hamstring 
 contributes to lateral rotation of the tibial bone while standing11 .
however , correlation between the tibial torsion angle and 
 the ratio of hamstring thickness has not been investigated in previous studies .
therefore , 
 the purpose of this study was to investigate the correlation between the tibial torsion 
 angle and the thickness ratio of the medial and lateral hamstring muscle to provide a 
 clinical guideline .
thirty male students of  b  university located in in cheonan , korea , were recruited for 
 this study .
all participants received verbal descriptions of the study procedures and signed 
 consent forms indicating agreement to participate in the study .
participants with orthopedic 
 disorders of lower limbs , drug ingestion , surgeries of lower limbs , and neurological leg 
 problems were excluded ( table 1table 1.general characteristics of the 
 participants ( n=30)age 
 ( yrs)height ( cm)weight 
 ( kg)22.3  2.3173.2  5.965.1
 
 11.4*values are expressed as mean  
 standard deviation ( sd ) ) .
all experimental 
 procedures were approved by the institutional review board ( approval number : 
 buirb-201606-hr-011 ) . *
values are expressed as mean  
 standard deviation ( sd ) this study used the ultrasonography device logiq p6 pro ( logiq p6 pro , ge inc . ,
scanning mode was b - mode , depth was 
 6  cm , frequency was 4  mhz , and a linear probe was used .
the participants lengths of greater trochanter and lateral epicondyle of the thigh were 
 determined with tape measures to ascertain the location of the biceps femoris ( bf ) , 
 semimembranosus ( sm ) and semitendinosus ( st ) in a prone position ( komeron corp .
, korea ) . 
 from the great trochanter of 60% spot , a vertical line was drawn using a marker pen . 

subjects had their knee flexed while the experimenter located the biceps femoris tendon 
 around the popliteal region .
the experimenter found the crossing point between the vertical 
 line and the biceps femoris tendon , and then a sticker was attached . in the same way
, 
 semimembranosus tendon inserts on medial popliteal line and origins from ischial tuberosity 
 of femur were located .
experimenter also found the crossing point using the same method 
 ( described above ) and attached a sticker .
measurements of hamstring thickness were done at 
 the sticker sites in position of subjects which had maintained body alignment in standing 
 position , not another movement10 .
methods of tibial torsion angle included transmalleolar axis ( tma ) and thigh foot angle 
 ( tfa ) .
the tma method measures the average angle 
 between the parallel line of femoral bone and the vertical line of connected line of lateral 
 and medial malleolus at the foot .
the data were obtained from the left and right side of the 
 legs with an average value of 3 repeated measures for higher intra - rater reliability . the 
 tibial torsion angle between vertical line and parallel line of femur
was measured using 
 image j program ( national institutes of health , usa ) .
pearson correlation coefficient was used to measure the average values 
 between the two variables expressed as percentage of muscle thickness ( bf thickness / st+ sm 
 thickness , bf thickness / st thickness , bf thickness / sm thickness ) and tibial torsion angle . 

there was no correlation between the right and left tibial torsion angle and st+sm 
 thickness divided into bf thickness .
additionally , it did not correlate with bf thickness / st 
 thickness and bf thickness / sm thickness when compared to the right and left tibial torsion 
 angle ( table 2table 2.pearsons correlation values between the 
 hamstring and tibial rotation on the right and left sidesbf/(sm+st ) bf / smbf / stl.ta0.0630.1570.99r.ta0.0180.0320.012bf : biceps femoris ; sm : 
 semimembranosus ; st : semitendinosus ; r.ta : right torsion angle ; l.ta : left torsion 
 anglevalues are expressed as mean  standard deviation 
 ( sd ) . ) .
: 
 semimembranosus ; st : semitendinosus ; r.ta : right torsion angle ; l.ta : left torsion 
 angle values are expressed as mean  standard deviation 
 ( sd ) .
in this study , we examined whether the ratio of the medial and lateral hamstring thickness 
 correlates with the tibial torsion angle .
we used three percentage values of the biceps 
 femoris , semimembranosus , and semitendinosus thickness in the thigh and the tibial torsion 
 angles obtained using ultrasonography .
we found that there is no correlation between the 
 three variables of the right and left legs and tibial torsion angle .
previously studied degrees of freedom of the tibio - femoral movement in seven 
 cadavers by looking at the independent muscle load of the medial and lateral hamstring 
 following anterior cruciate ligament injury .
they revealed that selective strength exercise 
 for the medial and lateral hamstring is needed to reduce the anterior cruciate ligament 
 injury ; furthermore , rehabilitation after injury is required because the medial and lateral 
 hamstring contributes to tibial rotation13 .
with regard to the selective hamstring atrophy generation by 
 muscle injury or anterior cruciate ligament reconstruction , lateral hamstring affects the 
 knee flexor activity and tibial rotation when measuring isokinetic strength of a 40 knee 
 flexion in normal young subjects14 . 
 similarly ,
imbalance of the medial and lateral hamstring activity correlates with tibial 
 rotation in a standing position with knees flexed to 90 in healthy adult male and female 
 subjects14 .
these reports show that the 
 medial and lateral hamstring contractions affect tibial rotation in the limb with the 
 cruciate ligament injury and a movement - recruited contraction .
however , correlation between 
 the medial and lateral hamstring and tibial rotation has never been investigated in a 
 position accompanied by knee flexion using ultrasonography in normal subjects .
the main reason for low correlation of the medial and lateral hamstring and tibial rotation 
 is the fact that the tibial torsion angle is influenced by many variables .
the movement of 
 the knee joint depends on both the passive movement of the bone and ligament and the active 
 muscle load15 .
especially , the screw - home 
 mechanism of the extended tibial bone is about a 20 lateral rotation in a fixed femur .
this 
 movement generates the end point for the extension and rotation of the knee .
the screw - home 
 mechanism is affected by the medial femoral condyle shape , passive tension of the anterior 
 cruciate ligament ( acl ) , and the medial and lateral meniscus , which has a larger space than 
 the medial meniscus located in tibiofemoral joint16 .
when the knee is flexed at 90 , these structures are influenced by 
 the tibial torsion angle which depends on the length of the acl , shape of the bone , and 
 meniscus .
the lateral tibial torsion angle increases in the presence of structural deformity 
 of the pelvic and ankle joint and the external rotator weakness of the pelvic joint6 .
also , it directly affects knee stability by 
 altering the torsion angle of two - joint muscles ( e.g. gastrocnemius ) and popliteal 
 structures .
it might be because the tibial torsion angle is related to arthrokinematics of 
 these structures and soft tissues .
measurements were only made in participants that were in a static standing position and did 
 not have enough hamstring contractions of the knee flexion .
further studies should be done 
 to assess the static posture following knee flexion with excessive hamstring contractions 
 and to assess dynamic posture changes resulting from knee extension and flexion without the 
 movement of other structures .
also , the patients with arthritis and acl injury accompany 
 with hamstring weakness could be done to study the correlation between tibial rotation and 
 hamstring thickness in upright standing position .
we conclude that the hamstring thickness 
 in a static standing position does not correlate with the tibial torsion angle during 
 ultrasound imaging evaluation of normal young subjects .
this study evaluated the correlation 
 between the tibial torsion angle and ratios of the medial and lateral hamstring muscle 
 thickness in a resting position .
these results 
 indicate that muscle contraction in a standing position does not affect the tibial torsion 
 angle in normal young adults .
 [ purpose ] to investigate the relationship between the lateral tibial rotation angle 
 during knee joint flexion and the medial and lateral hamstring muscle thickness ratio 
 during knee joint extension while resting , doing nothing , in upright standing position . 
 
 the lateral tibial torsion is an important factor of orthopedic knee joint diseases as 
 well as other weight bearing joint diseases such as osteoarthritis , meniscus syndrome , 
 anterior cruciate ligament rupture , etc . 
 [ subjects and methods ] thirty healthy young 
 adults participated in this study . 
 the thickness of the medial and lateral hamstrings was 
 measured using ultrasonographic imaging technique during knee extension in a resting 
 position . 
 the angle of tibial rotation was measured with 2d motion analysis during knee 
 flexion in a half kneeling position . 
 pearson s correlation coefficient was used to test 
 the relationship . 
 [ results ] there is no significant relationship between the angle of 
 lateral tibial rotation and the ratio of hamstring muscle thickness . 
 [ conclusion ] these 
 results demonstrate that lateral tibial rotation is not affected by hamstrings during rest 
 in a standing position . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION