***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 
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    Input: BACKGROUND There are no controlled , prospect i ve studies comparing the 10-year outcomes of anterior cruciate ligament ( ACL ) reconstruction using patellar tendon ( PT ) and 4-str and hamstring tendon ( HT ) autografts . HYPOTHESIS Comparable results are possible with HT and PT autografts . STUDY DESIGN Cohort study ; Level of evidence , 2 . METHODS One hundred eighty ACL-deficient knees that met inclusion criteria underwent ACL reconstruction ( 90 HT autograft , 90 PT autograft ) by one surgeon and were treated with an accelerated rehabilitation program . All knees were observed in a prospect i ve fashion with subjective , objective , and radiographic evaluation at 2 , 5 , 7 , and 10-year intervals . RESULTS At 10 years , there were no differences in graft rupture rates ( 7/90 PT vs. 12/90 HT , P = .24 ) . There were 20 contralateral ACL ruptures in the PT group , compared with 9 in the HT group ( P = .02 ) . In all patients , graft rupture was associated with instrumented laxity > 2 mm at 2 years ( P = .001 ) . Normal or near-normal function of the knee was reported in 97 % of patients in both groups . In the PT group , harvest-site symptoms ( P = .001 ) and kneeling pain ( P = .01 ) were more common than in the HT group . More patients reported pain with strenuous activities in PT knees than in HT knees ( P = .05 ) . Radiographic osteoarthritis was more common in PT knees than the HT-reconstructed knees ( P = .04 ) . The difference , however , was composed of patients with mild osteoarthritis . Other predictors of radiographic osteoarthritis were < 90 % single-legged hop test at 1 year and the need for further knee surgery . An " ideal " outcome , defined as an overall International Knee Documentation Committee grade of A or B and a radiographic grade of A at 10 years after ACL reconstruction , was associated with <3 mm of instrumented laxity at 2 years , the absence of additional surgery in the knee , and HT grafts . CONCLUSIONS It is possible to obtain excellent results with both HT and PT autografts . We recommend HT reconstructions to our patients because of decreased harvest-site symptoms and radiographic osteoarthritis Purpose Primary aim of the study was analysis of hamstring tendon regeneration after  anterior cruciate ligament reconstruction ( ACLR ) .  Secondary aim was analysis of isokinetic muscle strength in relation to hamstring regeneration . The hypothesis was that regeneration of hamstring tendons after ACLR occurs and that regenerated hamstring tendons contribute to isokinetic hamstring strength with regeneration distal to the knee joint line . Methods Twenty-two patients scheduled for ACLR underwent prospect i ve MRI analysis of both legs . MRI parameters were tendon regeneration and morphology , muscle retraction and muscle cross-sectional area . A double-blind , prospect i ve analysis of isokinetic quadriceps and hamstrings strength was performed . Results Regeneration of the gracilis tendon after ACLR occurred in all patients . Regeneration of the semitendinosus tendon occurred in 14 patients . At 1 year , the surface area of the semitendinosus and gracilis muscle decreased compared to both preoperatively ( P < 0.01 ) and the contralateral leg ( P < 0.01 ) . The cross-sectional area of the semitendinosus muscle decreased in the absence of tendon regeneration ( P = 0.05 ) . The cross-sectional area of the gracilis muscle was greater in case of regeneration distal to the joint line ( P = 0.01 ) . Muscle retraction of the semitendinosus muscle was increased in case of nonregeneration ( P = 0.02 ) . There was no significant relationship between isokinetic flexion strength and tendon regeneration . Conclusion Hamstring tendons regenerated after harvest of both semitendinosus and gracilis tendons for ACLR . There was no relation between isokinetic flexion strength and tendon regeneration . Level of evidence Prognostic study , Level II Abstract Coactivation of knee flexors during knee extension assists in joint stability by exerting an opposing torque to the anterior tibial displacement induced by the quadriceps . This opposing torque is believed to be generated by eccentric muscle actions that stiffen the knee , thereby attenuating strain to joint ligaments , particularly the anterior cruciate ligament ( ACL ) . However , as the lengths of knee muscles vary with changes in joint position , the magnitude of flexor/extensor muscle force coupling may likewise vary , possibly affecting the capacity for active knee stabilization . The purpose of this study was to assess the effect of changes in movement speed and joint position on eccentric/concentric muscle action relationships in the knees of uninjured ( UNI ) and post-ACL-surgery ( INJ ) subjects ( n = 14 ) . All subjects were tested for maximum eccentric and concentric torque of the contralateral knee flexors and extensor muscles at four isokinetic speeds ( 15 ° –60 ° · s−1 ) and four joint position intervals ( 20 ° –60 ° of knee flexion ) . Eccentric flexor torque was normalized to the percentage of concentric flexor torque generated at each joint position interval for each speed tested ( flexor E-C ratio ) . In order to estimate the capacity of the knee flexors to resist active knee extension , the eccentric-flexor/concentric-extensor ratios were also computed for each joint position interval and speed ( flexor/extensor E-C ratio ) . The results revealed that eccentric torque surpassed concentric torque by 3%–144 % across movement speeds and joint position intervals . The magnitude of the flexor E-C ratio and flexor/extensor E-C increased significantly with speed in both groups of subjects ( P < 0.05 ) and tended to rise with muscle length as the knee was extended ; peak values were generated at the most extended joint position ( 20 ° –30 ° ) . Although torque development patterns were symmetrical between the contralateral limbs in both groups , between-group comparisons revealed significantly higher flexor/extensor E-C ratios for the INJ group compared to the UNI group ( P < 0.05 ) , particularly at the fastest speed tested ( 60 ° · s−1 ) . The results indicate that joint position and movement speed influence the eccentric/concentric relationships of knee flexors and extensors . The INJ subjects appeared to accommo date to surgery by developing the eccentric function of their ACL and normal knee flexors , particularly at higher speeds and at more extended knee joint positions . This may assist in the dynamic stabilization of the knee at positions where ACL grafts have been reported to be most vulnerable to strain Seventy-two patients with subacute or chronic rupture of the anterior cruciate ligament were r and omly assigned to autograft reconstruction with four-str and gracilis and semitendinosus tendon ( N = 37 ) or with patellar tendon-bone ( N = 35 ) from the ipsilateral side . The groups were similar in terms of age , sex , level of activity , degree of laxity , meniscal lesions found surgically , and rehabilitation program . The follow-up was performed at another hospital by independent observers after 6 , 12 , and 24 months . Sixty-one patients ( 32 with hamstring tendon grafts and 29 with patellar tendon grafts ) complied with the follow-up routine for the full 24 months . No differences were found between the groups with respect to Cincinnati functional score , KT-1000 arthrometer measurements , or stairs hopple test results . The subjective result and the single-legged hop test result were better for the hamstring tendon group after 6 and 12 months , but no differences were found after 24 months . The hamstring tendon group showed better isokinetic knee extension strength than did the patellar tendon group after 6 months , but not after 12 and 24 months . There was a significant weakness in isokinetic knee flexion strength among the hamstring tendon group . Anterior knee pain was not significantly different between the groups , but kneeling pain was significantly less common in the hamstring tendon group after 24 months A more sports-specific and detailed strength assessment has been advocated for patients after anterior cruciate ligament ( ACL ) injury and reconstruction . The purpose of this study was to develop a test battery of lower extremity strength tests with high ability to discriminate between leg power development on the injured and uninjured sides in patients after ACL injury and in patients who have undergone ACL reconstruction . Twenty-three patients were tested 6 months after ACL injury and 44 patients were tested 6 months after ACL reconstruction . Twenty-four of the 44 patients were operated on using a hamstrings graft and 20 patients were operated on using a patellar tendon graft . All the patients performed a test battery of three strength tests for each leg in a r and omised order . The three strength tests were chosen to reflect quadriceps and hamstring muscular power in a knee-extension and a knee-flexion test ( open kinetic chain ) and lower-extremity muscular power in a leg-press test ( closed kinetic chain ) . There was a higher sensitivity for the test battery to discriminate abnormal leg power compared with any of the three strength tests individually . Nine out of ten patients after ACL reconstruction and six out of ten of the patients after ACL injury exhibited abnormal leg power symmetry using the test battery . Thus , this test battery had high ability in terms of discriminating between the leg power performance on the injured and uninjured side , both in patients with an ACL injury and in patients who have undergone ACL reconstruction . It is concluded that a test battery consisting of a  knee-extension , knee-flexion  and  leg-press muscle power test had high ability to determine deficits in leg power 6 months after ACL injury and reconstruction . Only a minority of the patients had restored leg muscle power . The clinical relevance is that the test battery may contribute to the decision-making process when deciding whether and when patients can safely return to strenuous physical activities after an ACL injury or reconstruction PURPOSE To investigate the influence of harvesting semitendinosus and gracilis tendons on the rotational muscle strength of the limb after  anterior cruciate ligament ( ACL ) reconstruction .  TYPE OF STUDY Prospect i ve study . METHODS We performed a prospect i ve study of 62 consecutive ( 34 male , 28 female ) patients with ACL reconstructions using the semitendinosus and gracilis tendons .  The mean age at surgery was 20.8 years .  The semitendinosus tendon was harvested in 32 patients ( ST group ) , and semitendinosus and gracilis tendons in 30 patients ( STG group ) . The peak isokinetic torques for extension , flexion , internal rotation , and external rotation were measured before and 12 months after ACL reconstruction using the Cybex 6000B system ( Cybex Division of Lumex , Ronkonkoma , NY ) . The rotational torque was measured at 30 degrees/sec and 120 degrees/sec . RESULTS Before reconstruction , the mean isokinetic peak torque of the involved limb was decreased in extension and internal rotation . The mean isokinetic peak torque of the involved limb in extension recovered 12 months after ACL reconstruction ; however , the weakness in internal rotation persisted . The preoperative weakness of the involved limb in extension and internal rotation recovered in the male patients , but not in the female patients after postoperative rehabilitation . The peak torque of the involved limb in internal rotation was decreased in the STG group , but not in the ST group . CONCLUSIONS The internal rotational torque was influenced by harvesting the semitendinosus and gracilis tendons after ACL reconstruction , especially in female patients and patients from whom the gracilis tendon was harvested . Semitendinosus and gracilis tendons are important for the internal rotation of the limb and it was difficult to compensate for this function . Thus , we recommend harvesting the semitendinosus tendon only if tendon quality is sufficient to further minimize harvesting morbidity Objectives : To analyze ligamentous stability and isokinetic strength of knee extensor and flexor muscles after  anterior cruciate ligament reconstruction  using 2 different autografts with identical fixation . Design : This study implements a comparative case series design . Setting : Schulthess Clinic , Switzerl and . Patients : A total of 153 consecutive patients ( n = 87 bone-patellar tendon-bone [BPTB]/66 quadruple semitendinosus/gracilis tendons [ QSGT ] patients ) who underwent BPTB and QSGT surgery  were functionally assessed . Intervention : All patients were functionally assessed ( knee extension/flexion isokinetic strength and knee joint laxity ) at a mean follow-up time of 11 months . Main Outcome Measurements : Laxity was measured utilizing the Kneelax arthrometer , whereas isokinetic strength of the knee extensor/flexor muscle groups was measured using the Biodex Multi Joint System 2 ( 180 ° /s and 300 ° /s ) . Results : The QSGT group had significantly greater knee joint laxity when compared with the BPTB group ( P < 0.001 ) . Furthermore , females in the QSGT group demonstrated the greatest knee joint laxity overall ( P < 0.001 ) . Additionally , a significant flexor torque deficiency was demonstrated in the QSGT group ( P < 0.001 ) ; however , no differences in extensor torque were observed . Conclusions : The use of a BPTB autograft achieved better knee joint stability as well as greater knee flexor torque than the QSGT autograft 
    Output:
    
Some of these deficits persisted up to 5 years after surgery .
Knee flexor strength is more impaired after ACL reconstruction with hamstring grafts and quadriceps strength after BPTB ACL reconstruction .
ConclusionS trength deficits of hip , knee and ankle muscles are reported after ACL reconstruction .
Muscular strength test may be an important tool to determine if an athlete can return to competitive sports after ACL reconstruction