anterior cruciate ligament ( acl ) injury is very common in sport activities and traffic 
 accidents , and may lead to an increased risk of meniscus and cartilage damage1 . in order to restore the stability of the 
 joint ,
enhance proprioception , and regain a normal movement , appropriate surgical treatment 
 and suitable rehabilitation training are necessary2 . at present , there are still some disputes about rehabilitation after reconstruction of the 
 anterior cruciate ligament , regarding the rehabilitation program , the choice of when to 
 begin training , and the outcome evaluation3 .
although conventional physical therapy is acceptable , a subject s 
 lower extremities functional recovery may be delayed by concerns over an inflammatory 
 reaction in the knee joint and loosening of the graft .
treadmill training with partial body - weight support has been shown to be effective in 
 neurologic rehabilitation4 .
treadmill 
 training follows modern principles of motor learning and allows subjects to practice complex 
 gait cycles early in rehabilitation before they can walk independently5 .
treadmill training with partial body - weight support and 
 conventional training have been compared after fracture of the femur neck and total hip 
 arthroplasty6 , 7 , and both treatment groups showed better and faster recoveries than 
 the control groups .
the purpose of this study was to investigate the effect of treadmill 
 training with early partial body weight support on the rehabilitation of anterior cruciate 
 ligament reconstruction .
the hypothesis was that treadmill training with partial body - weight 
 support would be more effective than conventional physical therapy at improving the lower 
 extremity function of subjects with anterior cruciate ligament reconstruction .
between january 2012 and january 2014 , 75 subjects with anterior cruciate ligament 
 reconstruction were recruited , and 40 met our inclusion criteria ( fig . 1fig .
nineteen subjects did not meet the inclusion criteria and sixteen subjects declined 
 to participate .
the inclusion criteria were : unilateral knee injury , preoperative mri 
 showing a rupture of the anterior cruciate ligament ; positive drawer test , lachman test , and 
 pivot shift test confirming the subjects had knee instability , but did not have meniscus , 
 cartilage , multiple ligament injuries and fractures ; willingness to participate in a 
 rehabilitation program ; anterior cruciate ligament reconstruction performed by the same 
 group of orthopedic surgeons ; and no other orthopedic or neurologic diseases impairing 
 gait .
flow diagram of the study all the subjects were treated with arthroscopic four strands of anterior cruciate ligament 
 reconstruction using autologous hamstring tendon , and fixed with a button plate and suture 
 plate suspension fixation system .
subjects were randomly and evenly ( 20 subjects per group ) 
 allocated to either the treatment group or the control group by choosing sealed envelopes 
 before the start of the intervention .
all 40 subjects were followed up for more than 24 
 weeks , and the clinical characteristics of the participants are presented in table 1table 1.clinical characteristics of the participants at the study onset ( n=40)treatment group(n=20)control group(n=20)age ( year)39.6  13.345.7  13.9male / female ( n)13/714/6weight ( kg)65.3  7.767.8  9.2height ( cm)171.2  10.4175.8  6.5body mass index ( kg / m)22.2  2.223.1  1.8left / right ( n)10/1011/9causes of injury(n)sports1516traffic54there were no significant differences between the groups at all baseline , 
 p>0.05 .. there were no significant differences between the groups at all baseline , 
 p>0.05 .
informed consent was obtained from all participants prior to the study and this study was 
 approved by the local ethics committee ( scientific research and ethics committee of the 
 affiliated taicang hospital of soochow university ) .
all the subjects were protected by a brace fixed at 0 degrees , to limit the knee angle 
 during training .
subjects attended the outpatient rehabilitation room , according to the plan 
 of rehabilitation training , 3 times per week .
the program of the subjects in the control group was as follows : 1 week post - operation : 
 quadriceps and hamstring muscles isometric contraction , passive joint flexion and extension 
 exercises ; 2 to 4 weeks post - operation : protective straight leg raises and partial 
 weight - bearing walking exercises ; 5 to 12 weeks post - operation : closed and open chain knee 
 extension , knee extensor resistance exercises , full weight bearing stretched and flexed 
 walking exercises , squat exercise , descending steps , balance board and power bicycle 
 exercise ; 1324 weeks post - operation : start to step forward and backward running , sideways 
 running and the  s  shape running practice .
in addition to performing the same training program as the control group , all subjects in 
 treatment group were asked to perform treadmill training with partial body weight support 
 with a brace limiting knee flexion to 60 degrees from 1 week post - operation .
initially , 
 subjects were encouraged to stand while bearing only some of their weight and shift their 
 gravity during standing .
the initial weight - bearing was 30% , with a 20% increase every week , 
 aiming for double lower limb full weight - bearing and the ability to shift gravity stably at 
 6 weeks .
subjects were trained to get accustomed to the feeling of standing on both legs , 
 and then try gravity shift training with the help of a posture correction mirror and 
 guidance from the therapist to correct their standing position .
the initial speed of the 
 treadmill was 0.2 m / s and was increased by 0.2 m / s every week ; the slope of the treadmill 
 was always 0 degrees .
full weight - bearing walking training lasted from 7 to 24 weeks 
 post - operation under the protection of crutches at treadmill speeds of 1.01.5 m / s .
the assessments included : a. circumference of lower extremities : the circumference of the leg was measured 10  cm 
 above the patella in the supine position , and was compared with the healthy side .
b. holden classification : holden walking capacity classified into 5 levels . c. ten - meter walking time at maximum gait speed : subjects 10  m walking time at the fastest 
 and most stable gait under the protection of a brace was recorded with an accuracy of 0.1 
 s. d. international knee documentation committee ( ikdc ) : knee functional score was evaluated 
 according to the ikdc score system .
e. knee joint stability : the stability of the knee joint was measured with a kt-1000 .
the results were analyzed using 
 the t - test ,  test and two - way anova .
the statistical software , spss 20.0 ( ibm , 
 usa ) , was used for the statistical analysis .
significant differences ( p<0.05 ) were found in the 
 holden classification , 10-meter walking time , circumference of the lower extremities and 
 ikdc scores between the two groups at 12 weeks post - operation . for most of the measures
, 
 there was no significant difference ( p<0.05 ) between the two groups at 24 weeks 
 post - operation ( table 2table 2.clinical resultsgroupikdckt1000 ( mm)difference in the circumference ( cm)holden10  m walking time ( s)12 weekstreatment ( n=20)63.14  10.92*n / a0.94  0.394.25  0.448.58  1.83control ( n=20)52.49  6.43n / a1.66  0.383.24  0.4412.70  0.3924 weekstreatment ( n=20)81.92  10.742.00  0.970.63  0.244.50  0.517.57  1.09control ( n=20)76.94  9.492.10  0.700.78 
interestingly , the values of the circumference of lower extremities , holden classification 
 and 10-meter walking time at 12 weeks post - operation in the treatment group were not 
 significantly different from their respective values in the control group at 24 weeks 
 post - operation ( p>0.05 ; table 3table 3.clinical resultsgroupikdckt1000 ( mm)difference in the circumference ( cm)holden10  m walking time ( s)12 weekstreatment ( n=20)63.14  10.92n / a0.94  0.394.25  0.448.58  1.8324 weekscontrol ( n=20)76.94  9.492.10  0.700.78  0.294.43  0.517.82  1.25significant difference between groups , p<0.01 . rest , p>0.05 .
anterior cruciate ligament injury may affect the stability of the knee joint , and the 
 proposition that early reconstruction helps to prevent secondary knee osteoarthritis and 
 meniscus injury has become the consensus .
however , the operation can only restore the static 
 structural stability , while dynamic stability and knee function recovery require early 
 scientific and appropriate rehabilitation training .
traditional rehabilitation program 
 options can generally be divided into conservative rehabilitation programs and aggressive 
 rehabilitation programs8 , 9 .
the former have the problems of a long recovery period and 
 low satisfaction among subjects , while the latter have the risk of implant loosening , bone 
 tunnel enlargement and swelling of the joint .
therefore , rehabilitation should vary from 
 person to person and be based on the principle of appropriate rehabilitation10 . in view of the fact that subjects after 
 acl reconstruction ca nt bear their total body - weights and to compensate for the slow 
 recovery of the knee joint , we introduced treadmill training with partial body - weight 
 support into the rehabilitation program .
walking is a complex and random movement that involves muscles of the whole body 
 cooperating to produce body displacement11 . the discomfort and instability of the knee joint after acl 
 reconstruction can lead to varying degrees of decline in walking efficiency12 .
the first demand of subjects undergoing 
 any surgery involving a low extremity joint is restoration of the pre - injury walking 
 condition , and this requires an improvement in the cooperative motion of multiple joints , as 
 well as the strength of the lower limb muscles .
however , during this period , subjects often 
 exhibit abnormal gait patterns due to pain from lower limb swelling , lack of muscle strength 
 and imbalance of the contralateral side13 .
treadmill training with partial body - weight support has already been 
 shown to be effective in neurologic rehabilitation4 .
treadmill training with partial body - weight support provides a 
 safer environment for the recovery of walking ability , gait correction and balance 
 adjustment than traditional physical therapy .
it combines weight - bearing , stepping and 
 stable balance , known as the three elements of walking , to promote the formation of normal 
 gait patterns14 .
furthermore , treadmill 
 training with partial body weight support is beneficial for the restoration of the stability 
 of positional control and limb coordination .
some researchers have reported that early activity training might cause joint laxity , and 
 encourage joint inflammation and joint effusion15 .
treadmill training with partial body weight support reduces the 
 muscle s contraction load on the lower extremity and promotes the development of lower 
 extremity muscle strength , as well as activity and weight - bearing capacities with a low 
 demand on muscle strength16 .
moreover , 
 treadmill training with partial body weight support can also make up for the absence of 
 closed kinetic chain training in the early stages due to insufficient muscle strength . in 
 the present research
, significant differences were found between the two groups ( p<0.05 ) 
 at the 12 weeks post - operation in the holden classifications , 10-meter walking time , the 
 circumferences of the lower extremities and ikdc scores .
interestingly , the circumference of 
 the lower extremities , holden classification and 10-meter walking time ( p>0.05 ) values at 
 12 weeks post - operation in the treatment group were not significantly different from their 
 respective values in the control group at 24 weeks post - operation , indicating that treadmill 
 training with partial body weight support improved walking stability and accelerated the 
 rehabilitation process by stimulating the coordination and balance functions of each muscle 
 group17 .
however , researchers have reported that early active rehabilitation may increase the risk 
 of implant loosening by blocking the revascularization process around the implant18 . closed kinetic chain exercise elicits 
 good recovery of knee joint function with low implant tension , while open kinetic chain 
 exercise better elicits muscle strength19 .
treadmill training with partial body weight support gait training 
 can be considered as a semi - open and semi - closed kinetic chain motion because of its low 
 demand on muscle strength .
the tension of the knee joint is largest between 060 degrees , so 
 the limiting angle was set to 60 degrees in the training .
the results show that treadmill 
 training with partial body weight support did not increase the risk of implant loosening or 
 rupture , and was a relatively safe way of moving , but the long - term effects on joint 
 stability need further observation .
treadmill training with partial body weight support varies from person to person depending 
 on the different features of the subject , and more attention should be paid to strengthening 
 the gluteal , quadriceps , hamstring and gastrocnemius muscles , in order to facilitate future 
 gait training20 . throughout the training 
 process
, the principle of slow and accurate , but not fast and unstable should be adhered to . 

special attention should be paid to the relationship between protection and training , and 
 treadmill training with partial body weight support provides a novel path to successful 
 rehabilitation in a way that gives the precise attention required .
it can improve and 
 accelerate the improvement of function of a subject s lower extremities without compromising 
 the stability of the knee joint in a given follow - up period
. limitations of this study were small sample size and the short - term follow - up period .
the 
 long - term stability of the knee , lower limb function and gait changes need further 
 observation .
stability tests relied on a physical examination , not magnetic resonance 
 examination , therefore , tendon bone healing and bone tunnel expansion could not be observed . 
 at our hospital , all anterior cruciate
ligament reconstruction operations are performed at 
 the acute stage , so a preoperative evaluation can not be carried out as accurately as 
 postoperatively .
a further control study is needed involving chronic anterior cruciate 
 ligament injury patients as subjects .
 [ purpose ] to compare the effects of treadmill training with partial body weight support 
 ( ttpbws ) and conventional physical therapy ( pt ) on subjects with anterior cruciate 
 ligament reconstructions . 
 [ subjects and methods ] a total of 40 subjects were randomly 
 allocated to either a treatment group or a control group . 
 subjects received either 
 treadmill training with partial body weight support ( treatment group ) or conventional 
 physical therapy ( control group ) . 
 the circumferences of the lower extremities , holden 
 classifications , 10-meter walking times and the international knee documentation committee 
 ( ikdc ) scores were compared at 12 and 24 weeks post - operation . 
 the knee joint stability 
 was tested at 24 weeks post - operation using a kt-1000 . 
 [ results ] significant differences 
 were found between the two groups at the 12 weeks post - operation . for most of the 
 measures 
 , there was no significant difference between the groups at 24 weeks 
 post - operation . 
 interestingly , for most of the measures , there was no significant 
 difference between their values in the treatment group at 12 weeks and their values in the 
 control group at 24 weeks post - operation . 
 [ conclusion ] the function of a subject s lower 
 extremities can be improved and the improvement was clearly accelerated by the 
 intervention of treadmill training with partial body weight support , without compromising 
 the stability of the knee joints in a given follow - up period . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION