***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background The effectiveness of anterior cruciate ligament reconstruction for restoring normal knee kinematics is largely unknown , particularly during sports movements generating large , rapidly applied forces . Hypothesis Under dynamic in vivo loading , significant differences in 3-dimensional kinematics exist between anterior cruciate ligament-reconstructed knees and the contralateral , uninjured knees . Study Design Prospect i ve , in vivo laboratory study . Methods Kinematics of anterior cruciate ligament-reconstructed and contralateral ( uninjured ) knees were evaluated for 6 subjects during downhill running 4 to 12 months after anterior cruciate ligament reconstruction , using a 250 frame/s stereoradiographic system .  Anatomical reference axes were determined from computed tomography scans .  Kinematic differences between the uninjured and reconstructed limbs were evaluated with a repeated- measures analysis of variance . Results Anterior tibial translation was similar for the reconstructed and uninjured limbs . However , reconstructed knees were more externally rotated on average by 3.8 ± 2.3 ° across all subjects and time points ( P = .0011 ) . Reconstructed knees were also more adducted , by an average of 2.8 ± 1.6 ° ( P = .0091 ) . Although differences were small , they were consistent in all subjects . Conclusions Anterior cruciate ligament reconstruction failed to restore normal rotational knee kinematics during dynamic loading . Clinical Relevance Although further study is required , these abnormal motions may contribute to long-term joint degeneration associated with anterior cruciate ligament injury/reconstruction Anterior cruciate ligament ( ACL ) injury can result in failure to return to pre-injury activity levels and future osteoarthritis predisposition . Single leg hop is used in late rehabilitation to evaluate recovery and inform treatment but biomechanical underst and ing of this activity is insufficient . This study investigated single leg hop for distance aim ing to evaluate if ACL patients had recovered : ( 1 ) l and ing strategies and ( 2 )  medio-lateral knee control . We hypothesized that patients with reconstructive surgery ( ACLR )  would have more similar l and ing strategies and knee control to healthy controls than patients treated conservatively ( ACLD ) . 16 ACLD and 23 ACLR subjects were compared to 20 healthy controls ( CONT ) .  Kinematic and ground reaction force data were collected while subjects hopped their maximum distance . The main output parameters were hop distance , peak knee flexor angles and extensor moments and Fluency ( a measure introduced to represent medio-lateral knee control ) . Statistical differences between ACL and control groups were analyzed using a general linear model univariate analysis , with COM velocity prior to l and ing as covariate . Hop distance was the smallest for ACLD and largest for CONT ( p<0.001 ; ACLD 57.1±14.1 ; ACLR 75.1±17.8 ; CONT 77.7±14.07 % height ) . ACLR used a similar kinematic strategy to CONT , but had a reduced peak knee extensor moment ( p<0.001 ; ACLD 0.32±0.14 ; ACLR 0.31±0.16 ; CONT 0.42±0.13 BW.height ) . Fluency was reduced in both ACLD and ACLR ( p=0.006 ; ACLD 0.13±0.34 ; ACLR 0.14±0.34 ; CONT 0.17±0.41 s ) . Clinical practice uses hopping distance to evaluate ACL patients ' recovery . This study demonstrated that aspects such as movement strategies and knee control need to be evaluated Functional dynamic tests are increasingly used in rehabilitation after injuries of the lower extremities . In these tests quantitative measures ( e.g. time , height , distance ) are mainly used as parameters , whereas the quality of the neuromuscular performance is poorly evaluated . In the present study the neuromuscular performance of leg muscles in different motor tasks was investigated 10 - 16 months after  ACL-reconstruction .  In 39 subjects with arthroscopically assisted ACL-reconstruction and 20 controls  , isometric knee extensor strength , thigh circumference , knee stability , subjective knee function and the neuromuscular performance ( by kinematic data and EMG ) during three dynamic tests ( stair descending , one-legged drop jump , one-legged cyclic hops ) were measured . During the strength measurements a superimposed twitch technique was used for the detection of neuromuscular inhibition . The results demonstrate a significantly reduced Lysholm-Score and a distinct strength deficit , but no neuromuscular inhibition and no differences in knee stability in the operated leg . Besides reduced motor abilities of the injured leg , significant differences of the neuromuscular performance could be detected . It was evident that different test conditions revealed different persisting changes of the neuromuscular performance , which could not be detected by kinematic parameters alone Purpose The effect of double-bundle ACL reconstruction on knee kinematics has recently been studied by several authors under controlled laboratory conditions however little evidence has been derived from dynamic in vivo evaluations . This study hypothesized that tibial rotation during pivoting motor tasks would be better restored after double-bundle ACL reconstructions when compared with single-bundle procedures . Methods Twenty patients with a chronic ACL rupture were r and omly assigned to receive a single- or double-bundle ACL reconstruction . Both knees were evaluated pre-operatively by kinematic 3-D gait analysis while performing low- and high-dem and motor tasks , including pivoting . At 6 months post-operatively , measurements were repeated in 16 patients . Ten healthy , sex- and age-matched subjects with no history of lower limb pathology formed the control group . The tibial rotational excursion was set as the dependent variable . Results The results indicate that at 6 months after surgery both “ anatomic ” single- and double-bundle ACL reconstruction are able to restore tibial rotational excursion when compared with the contralateral knees and with control knees from uninjured subjects . Chronic ACL-deficient patients show an increase in tibial rotation in both knees during high-dem and pivoting tasks . Conclusions Both “ anatomic ” single- and double-bundle ACL reconstruction adequately restore tibial rotational excursion in a human , “ in vivo ” kinematic model . As knee stability measurements by in vivo kinematic 3-D analysis more accurately represent actual knee loading during activities , the results of this study might better correlate with functional outcome after ACL reconstructions compared with static knee stability tests or ex vivo laboratory experiments . In such , the results of this dynamic study do not support the theoretical advantage of a double-bundle ACL reconstruction over an “ anatomic ” single-bundle ACL reconstruction . Level of evidence II Background : The restoration of knee rotational stability after  anatomic double-bundle anterior cruciate ligament ( ACL ) reconstruction  has been demonstrated in the cadaveric model and with passive stress tests on humans but not yet with dynamic functional biomechanical tests performed by human participants . Purpose : To prospect ively investigate the range of tibial rotation of ACL-deficient and ACL-reconstructed knees during a pivoting task . The authors hypothesized that there would be a significant increase in tibial internal rotation in the ACL-deficient knee compared with the contralateral knee and that the increased rotation would return to normal after anatomic double-bundle ACL reconstruction . Study Design : Case series ; Level of evidence , 4 . Methods : Ten men with unilateral ACL injury performed a high-dem and jump-l and ing and pivoting task before and after ACL reconstruction with mean follow-up of 11 months . The range of tibial rotation  of the injured , reconstructed , and intact knees during the pivoting movement was measured by an optical motion analysis system .  Paired t tests were performed to investigate any significant difference between the 2 limbs preoperatively and postoperatively and within the injured limb before and after the surgical treatment . Statistical significance was set at P < .05 . Results : The range of tibial rotation was higher in the ACL-deficient knee ( 12.6 ° ± 4.5 ° ) than in the intact knee ( 7.9 ° ± 3.1 ° ) preoperatively ( P < .05 ) . The increased rotation was reduced in the reconstructed knee ( 8.9 ° ± 3.0 ° ) after ACL reconstruction versus the intact knee postoperatively ( 8.2 ° ± 2.6 ° ) ( P < .05 ) . There was no significant difference in the tibial rotation between the intact knee and the reconstructed knee postoperatively ( P > .05 ) . Conclusion : As assessed with a dynamic functional pivoting movement , the anatomic double-bundle ACL reconstruction successfully restores knee rotational stability from an impaired level The relationships between extrinsic forces acting at the knee and knee kinematics were examined with the purpose of identifying specific phases of the walking cycle that could cause abnormal kinematics in the anterior cruciate ligament ( ACL ) deficient knee .  Intersegmental forces and moments in directions that would produce anterior-posterior ( AP ) translation , internal-external ( IE ) rotation and flexion-extension ( FE ) at the knee were compared with the respective translation and rotations of the tibia relative to the femur during four selected phases ( heel strike , weight acceptance , terminal extension and swing ) of the walking cycle . The kinematic changes associated with loss of the ACL occurred primarily during the terminal portion of swing phase of the walking cycle where , for the ACL deficient knee , the tibia had reduced external rotation and anterior translation as the knee extended prior to heel strike . The kinematic changes during swing phase were associated with a rotational offset relative to the contralateral knee in the average position of the tibia towards internal rotation . The offset was maintained through the entire gait cycle . The abnormal offsets in the rotational position were correlated with the magnitude of the flexion moment ( balanced by a net quadriceps moment ) during weight acceptance . These results suggest that adaptations to the patterns of muscle firing during walking can compensate for kinematic changes associated with the loss of the ACL . The altered rotational position would cause changes in tibiofemoral contact during walking that could cause the type of degenerative changes reported in the meniscus and the articular cartilage following ACL injury Purpose The purpose of this study was to test whether rotational knee kinematics during dynamic pivoting activities are predictive of subjective functional outcome ( IKDC , Lysholm ) , objective laxity scores ( KT max ) , and activity levels ( Tegner ) in patients after anterior cruciate ligament reconstruction ( ACLR ) . Methods Thirty-one patients with single-bundle ACLR were evaluated prospect ively with 3D-motion analysis during ( 1 ) descending a stairway and pivoting and ( 2 ) l and ing from a jump and pivoting . The side-to-side difference of tibial rotation range of motion ( SSDTR )  between the ACLR and the contralateral intact knee was calculated for the pivoting phase of each task . Linear regression models were applied with SSDTR , for each task predictors of the subjective IKDC score , Lysholm score , anterior tibial translation , and Tegner activity level . Results SSDTR for descending and l and ing were predictive of the IKDC subjective score ( R2 = 0.46 , p < 0.001 and R2 = 0.40 , p < 0.001 , respectively ) with “ medium ” effect sizes and of the Lysholm score ( R2 = 0.13 , p < 0.05 and R2 = 0.09 , n.s . ) with “ small ” to “ none ” effect sizes . SSDTR was not predictive of anterior translation or Tegner activity level ( n.s . ) . Conclusions Restoring rotational kinematics during dynamic pivoting activities after ACLR is predictive of functional outcome . The ability of the athlete after ACLR to control tibial rotation during pivoting activities may be predictive of functional outcome .Level of evidence Case series study . Level IV UNLABELLED The patellar and semitendinosus tendon autograft are the two most common techniques that orthopedic surgeons use to reconstruct the anterior cruciate ligament ( ACL ) . It has not been established , however , whether either of these techniques provides a greater functional advantage to the patient . PURPOSE To identify patients ' functional capabilities after reconstruction of the ACL with a patellar or semitendinosus tendon autograft . METHODS Forty male soccer players volunteered for the study and were assigned to three homogeneous groups : individuals who had patellar tendon reconstruction ( N = 15 ) , individuals who had semitendinosus tendon reconstruction ( N = 15 ) , and a control group ( N = 10 ) . All patients had undergone surgery 2 yr before this study and received the same  rehabilitation training . The testing procedures included measurement of thigh circumference , maximal isometric strength of quadriceps and hamstrings , two- and one-legged jump , squat and gait analysis . Kinetic , kinematic , and electromyographic data were collected . RESULTS The patellar tendon group exhibited lower ( P < 0.05 ) coactivation of the agonist and antagonist muscles around the knee joint during the squat movement and lower stabilization- and l and ing degrees during the jumps . Furthermore , the patellar tendon group had a shorter stance phase and reached the first vertical maximum later with the impaired leg while walking ( 720.2 + /- 15.6 ms vs 740.3 + /- 14.3 ms , and 24.3 + /- 0.64 % vs 22.9 + /- 0.74 % of stance phase ) , which was not observed in the semitendinosus tendon and control groups . CONCLUSION Functional performance is compromised in patients who undergo a patellar tendon graft compared with a semitendinosus graft , possibly due to an altered activation of the quadriceps and hamstring muscles OBJECTIVE Knee surgery may alter the neuromuscular response to unexpected perturbations during functional , dynamic tasks . Long latency reflexes ( LLR ) follow a transcortical pathway and appear to be modifiable by task dem and s , potentially giving 
    Output:
    
The appropriate selection of motion tasks is an integral factor in dynamic stability testing as it evokes different kinematic outcomes in relation to the different stages of ACLR recovery .
Stair negotiation and l and ing tasks are best performed during the early stages of recovery , and l and ing and pivoting are recommended 6 months after ACLR surgery .