patellofemoral pain syndrome ( pfps ) is a disease most commonly characterized by pain and 
 instability of the knee joint . in particular ,
knee weakness and discomfort or pain in the 
 anterior or posterior knee are observed when movements requiring weight bearing , flexion , 
 and extension are performed1 , 2 .
these movements include activities such as ascending and 
 descending stairs or a hill , squatting , sitting , standing , and exercising3,4,5,6 . 

pfps has a prevalence of 740% and is considered to be an overuse syndrome that is more 
 common in highly active young people and females7 , 
 8 .
patellofemoral pain and instability 
 are frequently overlooked in patients presenting with knee problems because most mechanical 
 derangements of the knee can instead be attributed to meniscus cartilage lesions9 .
further accumulation of injuries , 
 dislocation , or malalignment of the patella due to trauma or increased pressure on the 
 patella ( e.g. , from being overweight or lifting ) can also cause primary osteoarthritis .
this 
 can then result in osteoarthritis of the patellofemoral joint , a process that is accelerated 
 in overweight patients10 , 11 .
pfps is thought to be caused by abnormal movements 
 resulting from physical changes in the patellofemoral joint , namely , a mechanical imbalance 
 between the quadriceps and surrounding muscles .
patellofemoral joint pain can also be caused 
 by a knee sprain or other injury and results in instability during daily activities such as 
 ambulation12 , 13 .
although the symptoms and causes of pfps have been identified , the 
 criteria for measuring and evaluating patellofemoral joint pain remain inconsistent , leading 
 to differences in the reporting of results across different studies .
to more effectively 
 treat patellofemoral pain , which progresses in a scattered fashion , more systematic and 
 methodological research is needed .
therefore , the present study aimed to provide a basis for 
 developing a pain - attenuating and performance - enhancing treatment program by evaluating and 
 comparing ambulation patterns and knee function between people with and without 
 patellofemoral pain .
subjects consisted of 32 female patients in their 20s who were admitted to hospital and 
 diagnosed with pfps by a medical specialist ( pfps group ; 21.6  3.2  years ; 162.7  5.6  cm ; 
 52.8  7.0  kg ) and 25 adult females in their 20s without any abnormal findings ( control 
 group ; 21.1  2.2  years ; 161.5  4.1  cm ; 52.7  6.3  kg ) .
all subjects understood the purpose 
 of this study and provided their written informed consent prior to participation in the 
 study in accordance with the ethical standards of the declaration of helsinki . to measure 
 foot rotation
while walking , contact time ratios of the forefoot , midfoot , and heel in the 
 stance phase and the swing phase were measured as the subjects ambulated on a treadmill with 
 a built - in pressure plate ( fdm - t ; zebris medical gmbh , allgu , germany ) .
the treadmill was 
 set to a speed of 3.5  km / h , and measurements were recorded for 1 minute . the isokinetic 
 muscle function of the knee joint was the main experimental variable of the study and was 
 measured using the humac norm testing and rehabilitation system ( csmi , stoughton , ma , usa ) . 

subjects sat in the measurement chair and the torque of the knee joint was aligned with the 
 rotating axis of the dynamometer by adjusting the position with a table tube cross clamp and 
 a pedestal column clamp .
the thigh area and the upper body were tightly fixed using a strap 
 and a belt so that quadriceps exercise would not be affected by external force during 
 flexion and extension exercise of the knee joint resulting from moving areas other than the 
 joint being measured .
additionally , to isolate the muscle strength of the area of interest , 
 the ankle was fixed with a strap by adjusting the length of the lower leg and the adjustment 
 axis with an adapter ; afterward , flexion and extension exercise of the knee was performed . 

range of motion was determined by measuring the maximum flexion from the position in which 
 the joint was extended ( 0 ) in a sitting position .
subjects performed flexion and extension exercise of the lower limb 3 
 times below maximum and 1 time at maximum at angle speeds of 60/sec .
after measurements were recorded at 
 each speed , subjects were told to repeat flexion and extension of the knee joint .
the 
 measurement results were processed by spss for windows version 23.0 software ( spss inc . , 

chicago , il , usa ) . mean and standard deviation were calculated for each measurement variable 
 using the independent sample t - test , with p<0.05 indicating statistical significance .
ambulation patterns ( specifically the left and right forefoot contact ratios ) significantly 
 differed between the pfps group and control group ( table 1table 1.comparison of ambulation patternspfpg ( n=32)ng ( n=25)foot rotation ( deg)left5.8  1.45.8  1.7right7.3  2.77.3  2.4forefoot ( % ) left76.6 
3.379.5  5.3*right75.3  4.578.6  5.9*midfoot ( % ) left68.6  4.168.4  5.1right68.3  3.969.3  4.1heel ( % ) left59.8  5.459.2  7.6right59.3  5.659.6  7.2pfpg : patellofemoral pain group ; ng : normal group .
values are mean  sd , 
 * p<0.05 ) . during the isokinetic muscle strength test , left and right knee extensor and 
 flexor torques also significantly differed between the two groups ( table 2table 2.comparison of isokinetic muscle strength of the knee jointspfpg ( n=32)ng ( n=25)extensor ( nm)left81.1  18.6115.4  21.5***right84.7  14.8135.1  15.4***flexor ( nm)left51.4  15.171.9  13.6***right53.0  13.180.8  13.3***pfpg : patellofemoral pain group ; ng : normal group .
values are mean  sd , 
 * p<0.05 pfpg : patellofemoral pain group ; ng : normal group .
pfps has diverse causes and is mostly observed while performing daily activities that bear 
 weight on the knee .
observations include pain and clicking in the knee joint when 
 weight - bearing movements are performed for long periods14 .
other typical symptoms include recurrence of restricted movement 
 and confined range of motion of the knee joint15 .
these recurring aberrations are characterized by defects in 
 proprioception and muscle reflexes around the knee joint , which can be caused by both acute 
 and chronic damage16 , 17 .
these problems can eventually cause muscle weakness and chronic 
 abnormal movements such as malalignment and giving - way of the knee during ambulation13 , 18 .
ambulation , which is the most basic daily movement of humans , is a 
 functional movement produced by symmetrical and continuous alternations between the stance 
 and swing phases .
the pressure transmitted to the patellofemoral joint during ambulation or 
 during ascending and descending of stairs is 0.5- to 6-times that of body weight19 , 20 .
this increased burden on the knee joint , which is due to an 
 increased knee flexion angle caused by increased knee extension movement , enhances 
 patellofemoral pain21 , 22 .
the present study showed that the forefoot contact ratio 
 was significantly higher in the pfps group than in the control group , which is consistent 
 with past research21 , 22 .
this difference can therefore be attributed to decreased stance 
 contact caused by increased stress on the patellofemoral joint during ambulation . 

patellofemoral joint pain can also be related to weakening of the quadriceps and hamstrings . 

the quadriceps muscles 
 are the main extensors of the knee and are responsible for bearing body weight and 
 facilitating balancing abilities such as body alignment , stabilization , and ambulation23 . when the extension function of the knee 
 is weakened , functional impairments such as malalignment are produced , potentially causing 
 pfps2 , 24 . weakened extensor muscle strength due to weakened extension 
 function can , in turn , produce pain or other ailments18 . in agreement with this ,
the pfps group in the present study showed 
 significantly lower extension and flexion strength than did the control group .
these results 
 demonstrate that an abnormal decrease in muscle strength can be used as an indicator of 
 pfps , thereby aiding in the prevention of its pathogenesis .
one strategy for prevention is 
 isokinetic muscle exercise , which is necessary for efficient functional enhancement25 .
it has been shown that pain - alleviating 
 rehabilitation can successfully treat two - thirds of pfps patients26 . in conclusion
, the present study demonstrates that basic 
 analysis based on ambulation patterns and muscle strength , along with the evaluation of 
 electromyograms , motion analysis , and ground reaction force , can provide relevant 
 information about functional recovery from pfps .
importantly , this was not previously 
 possible with fractional evaluations of muscle exercise , balance , and flexibility .
the 
 present study may also have implications beyond the treatment of pfps , potentially providing 
 insight for improving the rehabilitation process of patients with other types of anterior 
 knee joint lesions .
 [ purpose ] the aim of this study was to evaluate the differences in the ambulation 
 patterns and knee joint performance between people with and without patellofemoral pain . 
 the present study also aimed to utilize these results as a basis for the development of 
 pain - alleviating and performance - improving treatment programs . [ subjects and methods ] 
 subjects consisted of 32 adult females diagnosed with patellofemoral pain syndrome and 25 
 adult females without patellofemoral pain ( controls ) . 
 contact ratio patterns during 
 ambulation and isokinetic muscle strength around the knee joint were measured in both 
 groups and then compared . 
 [ results ] ambulation patterns , specifically the contact ratios 
 of the left forefoot and right forefoot , differed significantly between patients with 
 patellofemoral pain syndrome and controls . 
 an isokinetic muscle strength test demonstrated 
 that left and right knee extensor and flexor torques also significantly differed between 
 these two groups . [ conclusion ] basic analysis based on ambulation patterns and muscle 
 strength can be used to indicate functional recovery from patellofemoral pain syndrome and 
 provide insight into improving the rehabilitation of patients . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION