The isometric and isokinetic knee extension and flexion muscle strength profile of elite soccer players

BACKGROUND

This study aimed to further complete normative data sets for the strength profile of the thigh in soccer players by performing isometric and isokinetic measurements in a large sample per player position.

METHODS

In total, 364 soccer players were divided into subgroups according to their pitch position. All players performed isometric and isokinetic strength measurements during active competition period using an isokinetic dynamometer (System 3, Biodex®, ENRAF-NONIUS, New York, USA).

RESULTS

Isokinetic strength of m. Quadriceps was significantly (p = 0.023) higher in strikers compared to central midfielders in both the dominant (+ 9%) and the non-dominant (+ 4%) leg. No further differences were found in isometric or isokinetic strength per playing positions.

CONCLUSIONS

We have shown that strength profiles do not differ between playing positions on the field. This is valuable information for elite soccer high performance coaches and medical staffs aiming to improve daily training efficiency and rehabilitation of their players.

Reasons for Not Returning to Pre-injury Sport Level After ACL-Reconstruction

The study aimed to identify athlete-reported reasons for not returning to pre-injury sports level after anterior cruciate ligament reconstruction (ACLR) and to identify the factors associated with these reasons. Ninety-one athletes with 2 years post-ACLR indicated whether or not they had returned to their pre-injury sport level (same frequency, duration, and intensity). Athletes who did not return were asked to provide the reasons. Athletes' characteristics and injury-related factors were used to determine factors associated with the reasons for not returning. Only nine athletes (10%) returned to pre-injury sport level after ACLR. The most common reasons for not returning were lack of confidence or concerns about re-injury (48.8%), followed by continued post-surgical impairments in the reconstructed knee (39%). Having episodes of the knee giving way after ACLR was the only significant predictor of post-surgical impairments (48.8%; OR=8.3, 95%CI=2.48-27.42, p=0.001). Lack of confidence, concerns about re-injury, or post-surgical impairments in the reconstructed knee were the most frequently reported reasons for not returning to pre-injury sports level with 2 years post-ACLR. Reported dynamic knee instability was the only factor associated with ongoing post-surgical knee impairments after ACLR. Rehabilitation programs should address athletes' psychological responses and resolve knee impairments to optimize return to pre-injury sport level after ACLR.

Athletes Continue to Show Functional Performance Deficits at Return to Sport After Anterior Cruciate Ligament Reconstruction: A Systematic Review

PURPOSE

To systematically review the existing literature on the functional performance of athletes at the time of return-to-sport (RTS) clearance after anterior cruciate ligament reconstruction (ACLR).

METHODS

A systematic literature search of the MEDLINE, EMBASE, Scopus, and Web of Science databases was performed. The inclusion criteria were original research reports with study populations of athletes who had undergone ACLR and had undergone objective functional testing immediately after clearance to RTS. Functional testing was stratified by hop tests, strength tests, kinetic assessment, and kinematic assessment, and data were extracted from each study using a standardized template.

RESULTS

Of the 937 unique studies identified, 46 met the inclusion criteria. The average time between ACLR and functional testing was 7.9 months among the included studies. In 10 of 17 studies, patients were found to have an average quadriceps strength limb symmetry index of less than 90%. However, only 2 of 12 studies found the average hop test limb symmetry index to be less than 90%. Kinematics included reduced knee flexion angle and increased trunk flexion on landing in ACLR patients compared with matched controls. On evaluation of kinetics, ACLR patients showed reduced peak vertical ground reaction force, lower peak knee extension and knee flexion moments, and altered energy absorption contribution compared with matched controls.

CONCLUSIONS

This systematic review suggests that athletes show functional deficits at the time of RTS at an average of 7.9 months after ACLR. Traditional functional tests, such as strength and hop tests, are not able to accurately identify patients who continue to show deficits. The most common biomechanical deficits that persist after RTS clearance include diminished peak knee extension moment, decreased knee flexion angle, increased trunk flexion angle, reduced vertical ground reaction force, and increased hamstring central activation ratio during various functional gait and landing tasks.

LEVEL OF EVIDENCE

Level III, systematic review of Level I to III studies.

Return to sports after an ACL reconstruction in 2024 - A glass half full? A narrative review

A successful return to sports (RTS) after an anterior cruciate ligament reconstruction (ACLR) is multifactorial, and therefore difficult and challenging. Unfortunately, low percentages of patients RTS, and for those who succeed, one-fifth of patients will sustain a second ACL injury. Over the past years, test batteries were developed to assess whether patients can RTS with a low risk for a second ACL injury risk. Low rates of patients who meet RTS criteria were found, coupled with the insufficiency of current RTS test batteries in predicting second ACL injuries suggesting poor sensitivity. The result of an RTS test is likely to reflect the content of a rehabilitation program, raising critical questions regarding what we are offering patients within the rehabilitation programme. Are we preparing our patients well enough for the high demands of complex situations within pivoting team sports? This narrative review offers insights from key lessons of the last 15 years on 1) RTS testing, 2) the content of rehabilitation, and 3) the RTS continuum, all from a "helicopter perspective".

Intra- and inter-limb strength imbalance and asymmetry in soccer: A comparison of elite senior and junior players

Evaluation of muscle strength imbalance can be an important element in optimizing the training process of soccer players. The purpose of the study was to examine isokinetic peak torque (PT) and total work (TW) exerted by both knee extensors (quadriceps or Q) and flexors (hamstrings or H), intra-limb imbalance and the magnitude and direction of inter-limb asymmetry in top elite senior (n = 109) and junior (n = 74) soccer players. An isokinetic dynamometry was used to measure maximum peak torque of quadriceps (PT-Q) and hamstrings (PT-H) at an angular velocity of 60° ·s-1, as well as the total work for extensors (TW-Q) and flexors (TW-H) at an angular velocity of 240° ·s-1 in the dominant (DL) and non-dominant leg (NDL) during concentric muscle contraction. Intra-limb imbalance and inter-limb asymmetries were calculated using a standard equation. Statistical analysis using t-test and Mann-Whitney U-test revealed: (a) no differences (p > 0.05) between groups for PT-Q and PT-H, (b) greater strength levels (p < 0.05) for TW-Q and TW-H of senior players than juniors, and (c) no differences (p > 0.05) between groups for intra-limb imbalance and inter-limb asymmetry. Additionally, Pearson's chi-kwadrat (χ2) analysis showed no differences (p > 0.05) between groups for intra-limb imbalance and inter-limb asymmetry in relation to the 'normative' values accepted in the literature that indicate an increase in the risk of knee injury. This study shows that isokinetic assessment can be an important tool to identify imbalances/asymmetries and to develop strategies to reduce the risk of muscle injury.

Rehabilitation and Return to Play Protocols After Anterior Cruciate Ligament Reconstruction in Soccer Players: A Systematic Review

BACKGROUND

Rehabilitation after anterior cruciate ligament ACL reconstruction (ACLR) is crucial for safe return to play (RTP) and reducing the chances of a reinjury. Yet, there is no consensus on the ideal functional tests to assess rehabilitation progress in soccer players after ACLR.

PURPOSE

The primary objective was to highlight the existing gap in the literature concerning the most effective standardized rehabilitation protocols and testing for facilitating successful RTP among soccer players.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A systematic review using PubMed, Embase, and the Cochrane Central Register of Controlled Trials (CENTRAL) was conducted. Inclusion criteria encompassed original studies (level of evidence 1-4) that examined rehabilitation protocols, metrics of knee rehabilitation, and clinical outcomes after ACLR in soccer players.

RESULTS

This review incorporated 23 studies, predominantly retrospective case series, with a total number of 874 soccer players who underwent ACLR and rehabiliation. 5 (21.7%) studies utilized an accelerated rehabilitation protocol, while 7 (30.4%) of studies utilized a criterion-based rehabilitation. A wide heterogeneity of data was extracted including functional tests of rehabilitation and RTP such as strength test batteries, hop test batteries, and movement quality assessments. Of the 23 selected studies, 2 (8.7%) used all 3 test batteries, 8 (34.8%) used 2 test batteries, 12 (52.2%) used 1 test battery, and 1 (4.3%) used 0 of the test batteries. The mean time between surgery and RTP ranged from 3 to 8 months with only 2 (8.7%) studies reporting complications after ACLR. Lastly, out of the total studies examined, 9 (39.1%) assessed patient-reported outcome measures (PROMs), all of which demonstrated significant improvement from the initial assessment to the final follow up.

CONCLUSION

Soccer-specific rehabilitation after ACLR lacks standardization. Even though many studies have assessed protocols for optimal RTP and reduced secondary ACL injuries, there is a gap in the literature regarding the most effective protocols and RTP testing. The methodology reported by Kyritsis et al could serve as a foundation for future prospective randomized multicenter studies to establish a standard rehabilitation protocol and enable a successful return to soccer.

Clinical Outcomes After ACL Reconstruction in Soccer (Football, Futbol) Players: A Systematic Review and Meta-Analysis

CONTEXT

The risk factors for anterior cruciate ligament (ACL) tear for athletes participating in pivoting sports includes young age and female sex. A previous meta-analysis has reported a reinjury rate of 15% after ACL reconstruction (ACLR) for athletes across all sports. To the best of the authors' knowledge, this is the first systematic review and meta-analysis of available literature reporting outcomes after ACLR in soccer players.

OBJECTIVE

To review and aggregate soccer-specific outcomes data after ACLR found in current literature to help guide a more tailored discussion regarding expectations and prognosis for soccer players seeking operative management of ACL injuries.

DATA SOURCES

A comprehensive search of publications was performed using PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and SPORTDiscus databases.

STUDY SELECTION

Inclusion criteria consisted of original studies, level of evidence 1 to 4, studies reporting clinical and patient-reported outcomes (PROs) after primary ACLR in soccer players at all follow-up length.

STUDY DESIGN

The primary outcomes of interest were graft failure/reoperation rates, ACL injury in contralateral knee, return to soccer time, and PROs.

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

Search of literature yielded 32 studies for inclusion that involved 3112 soccer players after ACLR.

RESULTS

The overall graft failure/reoperation rate ranged between 3.0% and 24.8% (mean follow-up range, 2.3-10 years) and the combined ACL graft failure and contralateral ACL injury rate after initial ACLR was 1.0% to 16.7% (mean follow-up range, 3-10 years); a subgroup analysis for female and male players revealed a secondary ACL injury incidence rate of 27%, 95% CI (22%, 32%) and 10%, 95% CI (6%, 15%), respectively. Soccer players were able to return to play between 6.1 and 11.1 months and the majority of PROs showed favorable scores at medium-term follow-up.

CONCLUSION

Soccer players experience high ACL injury rates after primary ACLR and demonstrated similar reinjury rates as found in previous literature of athletes who participate in high-demand pivoting sports.

Assessment of Return to Sport After ACL Reconstruction With Soft Tissue Autograft in Adolescent Athletes: Quadriceps Versus Hamstring Tendon

Background

Quadriceps tendon soft tissue autograft represents an increasingly popular graft option for anterior cruciate ligament reconstruction (ACLR), particularly for adolescents, some of whom have an open physis, precluding use of graft options with bone plugs.

Purpose/Hypothesis

The purpose of this study was to quantify return-to-sport performance assessments in adolescents at 6 months after ACLR with all-soft tissue quadriceps tendon autograft (ACLR-Q) versus hamstring tendon autograft (ACLR-HS). It was hypothesized that ACLR-Q would be associated with improved hamstring strength and hamstring-to-quadriceps (HS:Q) ratios compared with ACLR-HS, albeit with decreased quadriceps strength.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Included were patients aged 12 to 19 years who underwent primary ACLR by a single surgeon and who completed a return-to-sport performance assessment between 5 and 9 months postoperatively. The performance assessment included manual muscle strength tests (hamstring, quadriceps, hip abductor and adductor), dynamic balance test (Y-balance), and functional hop tests (single hop, triple hop, crossover hop, 6-m timed hop). Data were converted to limb symmetry indices, and limb symmetry index deficits were compared between the ACLR-Q and ACLR-HS cohorts using the Student t test or Wilcoxon-Mann-Whitney test.

Results

An initial cohort of 90 ACLR-Q patients was compared with 54 ACLR-HS patients, with no significant differences in patient characteristics. Differences in meniscal repair rates, however, prompted use of propensity score matching on age, sex, body mass index, meniscectomy, and meniscal repair to produce comparable subcohorts. The matching resulted in 67 ACLR-Q and 52 ACLR-HS patients. Hamstring strength deficits were significantly greater in ACLR-HS versus ACLR-Q patients (-40.5% vs -5.7%; P < .001). Quadriceps strength deficits were significantly greater in ACLR-Q versus ACLR-HS patients (-12.8% vs -0.4%; P < .001). ACLR-Q patients had a significantly greater HS:Q ratio on the operative knee (P < .001) and significantly higher Y-balance composite score deficits (-2.9% vs -0.4%; P = .01) than ACLR-HS patients. There were no significant differences in hop test performance between groups.

Conclusion

Adolescent athletes who underwent ACLR-Q showed significantly greater quadriceps strength deficits but significantly smaller hamstring strength deficits than those who underwent ACLR-HS, leading to more favorable HS:Q ratios in ACLR-Q patients at 6 months postoperatively.

Isokinetic Muscle Strength in Elite Soccer Players 3 and 6 months After Anterior Cruciate Ligament Reconstruction

ABSTRACT

Milutinović, A, Jakovljević, V, Dabović, M, Faude, O, Radovanović, D, and Stojanović, E. Isokinetic muscle strength in elite soccer players 3 months and 6 months after anterior cruciate ligament reconstruction. J Strength Cond Res 37(4): e297-e304, 2023-The aim of this study was to evaluate interlimb symmetry in quadriceps and hamstring peak torque of elite soccer players at 3 months (stage 1) and 6 months (stage 2) after anterior cruciate ligament (ACL) reconstruction. Eight male professional soccer players competing at the highest level across different European countries, who had undergone ACL reconstruction, participated in this study. All patients underwent a supervised physiotherapy program after surgery. Data analyses included the use of separate two-way repeated-measures analyses of variance and effect sizes. Although knee extensor and flexor strength of the non-injured limb was found to be relatively unaltered ( g = -0.10 to 0.00) between stage 1 and stage 2, comparisons across time points revealed moderate improvements in quadriceps peak torque ( p = 0.01, g = 0.52), hamstring peak torque ( p = 0.07, g = 0.51), and hamstring:quadriceps (H/Q) ratio ( p = 0.03, g = -0.68) of the injured leg, as well as small-large improvements in the quadriceps ( p = 0.004, g = 1.24) and hamstring limb symmetry index (LSI) ( p = 0.056, g = 0.41). A time-dependent moderate-large asymmetry observed at stage 1 between the injured and noninjured leg in quadriceps peak torque ( p < 0.001, g = -1.83), hamstring peak torque ( p = 0.157, g = -0.67), and the H:Q ratio ( p = 0.06, g = 1.01), as well as between the hamstring and quadriceps LSI ( p = 0.03, g = -0.74) was eliminated at stage 2 ( g = -0.31 to 0.42). Our findings indicate the importance of supervised and comprehensive therapy, as well as strength screening to assist in recovery aimed at optimizing identified strength deficits following ACL reconstruction.

The Relationship between Lower Extremity Functional Performance and Balance after Anterior Cruciate Ligament Reconstruction: Results of Patients Treated with the Modified All-Inside Technique

BACKGROUND AND OBJECTIVES

Anterior cruciate ligament (ACL) ruptures are common injuries, and ACL reconstruction (ACLR) is among the most common surgical procedures in sports surgery. Our research aims to compare the 6-month post-operative results of the modified all-inside (MAI) ACLR technique, single leg hop tests (SLHT), and Y balance tests applied in different directions on the operated and non-operated sides.

MATERIALS AND METHODS

A retrospective cohort of 22 male recreational athletes who underwent MAI ACLR techniques performed by the same surgeon were evaluated. The functional knee strengths of the participants on the operated and non-operated sides were evaluated with five different tests of SLHTs: single hop for distance (SH), triple hop for distance (TH), crossover triple hop for distance (CH), medial side triple hop for distance (MSTH), and medial rotation (90°) with hop for distance (MRH). Their dynamic balance was evaluated with the Y balance Test.

RESULTS

Compared to pre-operative levels, there was a significant improvement in the mean Lysholm, Tegner, and IKDC scores during the post-operative period (p < 0.05). There was a difference between SH, THD, CHD, MSTH, and MRH on the operated and non-operative sides (p < 0.05). There was no difference between Y balance scores on the operated and non-operative sides, and there were no differences between LSI scores resulting from SLHTs (p > 0.05). There were no significant relationships between YBT (composite scores) and SH, TH, CH, MSTH, and MRH distances in the healthy leg (p > 0.05), but a significant correlation with only CH in the ACL leg (p < 0.05).

CONCLUSIONS

Our research shows that sixth-month post-operative SLHT findings were lower on the ACL side compared to the healthy side in patients tested with the MAI ACLR technique. However, when these scores are evaluated in terms of balance, it can be seen that both sides reveal similar findings. The similarity of LSIs in SLHTs applied in different directions, and balance scores of ACL and healthy sides revealed that the MAI technique is also an ACLR technique that can be used in athletes from a functional point of view.

Association Between Isokinetic Knee Strength Characteristics and Single-Leg Hop Performance In Healthy Young Participants

Objective

The purpose of this study was to determine the extent to which the mean peak moment (MPM) of knee flexors and extensors could predict performance in a group of healthy individuals.

Methods

Eighty-four healthy individuals-32 men and 52 women (mean age, 22.1 ± 3 years; range, 18-35 years)-participated in this study. Isokinetic unilateral concentric knee flexor and extensor MPM was assessed isokinetically at angular velocities of 60°/s and 180°/s. Functional performance was assessed using the single hop of distance (SHD).

Results

Positive moderate to good statistically significant correlations (r = .636 to r = .673) were found between knee flexor and extensor MPM at 60°/s and 180°/s for the SHD test. Knee flexor and extensor MPMs are strong predictors for the SHD test at 60°/s and 180°/s (R2 = .40 to R2 = .45).

Conclusion

Knee flexor and extensor strength was substantially correlated with SHD.

Range of Motion, Strength, and Function After ACL Reconstruction Using a Contralateral Patellar Tendon Graft

BACKGROUND

Regaining preinjury levels of activity and progressing rehabilitation factors after anterior cruciate ligament (ACL) reconstruction have shown mixed results.

PURPOSE

To evaluate the timing and rate of return for knee range of motion (ROM), stability, strength, and subjective scores after ACL reconstruction with contralateral patellar tendon graft (PTG).

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Included were 2148 patients (1238 male patients, 910 female patients) who underwent primary ACL reconstruction with a contralateral PTG between 1995 and 2017 and had complete objective data through 3 months of follow-up. All patients participated in a rehabilitation program specific to goals for each knee. Patients were evaluated objectively with goniometric measurement of ROM, isokinetic quadriceps strength testing, and laxity with a KT-2000 arthrometer. Subjective data were collected at 2 and 5 years.

RESULTS

Normal extension on the reconstructed knee was attained for 95% of patients at 1 week postoperatively; normal flexion on the reconstructed knee was reached by 77% of patients by 3 months. At 3 months postoperatively, mean limb symmetry index strength was 104%, and the strength on the ACL-reconstructed and graft-donor knees was 87% and 86% of their respective preoperative strength. Mean manual maximum side-to-side difference in laxity was 2.0 mm at 1 month. Most patients (90%) returned to level 8 sports or higher and did so at an average of 5.7 months. Mean International Knee Documentation Committee scores for the ACL-reconstructed and graft-donor knees were 89 and 91 at 2 years (n = 1015 patients) and 84 and 90 at 5 years (n = 1275 patients), respectively. Mean Cincinnati Knee Rating Scale scores for the ACL-reconstructed and graft-donor knees were 92 and 96 at 2 years (n = 1184) and 88 and 94 at 5 years (n = 1236), respectively.

CONCLUSION

For patients who underwent ACL reconstruction with a contralateral PTG, postoperative ROM and strength were restored quickly by splitting the rehabilitation into different goals between the two knees. Using a contralateral PTG, this structured rehabilitation plan can lead to a relatively quick return to sport and good subjective long-term outcomes.

Bilateral Alterations in Isokinetic Strength and Knee Biomechanics During Side-Cutting 1 Year After Unilateral ACL Reconstruction

BACKGROUND

Individuals with anterior cruciate ligament (ACL) reconstruction (ACLR) are a population that has a higher risk for ACL injury compared with the general population. To reduce the reinjury rate and improve the rehabilitation outcome after ACLR, risk factors for ACL injury have to be addressed.

PURPOSE

To compare the knee biomechanics during side-cutting and isokinetic strength of the thigh muscle of the reconstructed leg with those of the contralateral leg and healthy controls and investigate the knee movement asymmetries in individuals with ACLR.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 16 participants with ACLR (ACLR group; 11.8 ± 1.1 months after reconstruction) and 16 healthy controls (control group) were recruited. Landmark coordinates and ground-reaction forces during side-cutting and isokinetic strength of hamstring and quadriceps were collected. Two-way analysis of variance with the mixed design was performed to compare each dependent variable between groups and across legs.

RESULTS

The reconstructed leg had a significantly smaller knee flexion angle (P = .004) and less quadriceps strength (P = .003) than the contralateral leg. The knee extension moment and knee external rotation angle were decreased compared with both the contralateral leg (P = .001, P = .003, respectively) and the healthy control leg (P = .001, P = .001, respectively). The ACLR group showed greater knee abduction angles (P = .004) and smaller knee external rotation moments (P = .006) than the control group. The ACLR group also demonstrated greater asymmetries of knee flexion angle (P = .015), knee external rotation angle (P = .001), knee extension moment (P = .013), knee abduction moment (P = .001), and quadriceps strength (P = .046) than the control group.

CONCLUSION

Knee biomechanics in the leg with ACLR were altered mainly in the sagittal plane during side-cutting compared with the contralateral leg. The altered movement patterns between the ACLR and control groups were primarily observed in the frontal and transverse planes. The ACLR group also demonstrated greater asymmetries of sagittal knee movement and concentric quadriceps strength than the control group.

CLINICAL RELEVANCE

Individuals with ACLR showed different alterations in the reconstructed and contralateral leg compared with healthy controls. These results suggest that rehabilitation programs after ACLR should further focus on restoring the knee flexion angle and quadriceps strength. Injury prevention programs need to be further targeted in the altered movement patterns observed between the ACLR and the healthy groups.

Reactive strength index during single-limb vertical continuous jumps after anterior cruciate ligament reconstruction: cross-sectional study

BACKGROUND

The association of the reactive strength index (RSI) during single-limb vertical continuous jumps (SVCJs) with single-limb hop tests in athletes after anterior cruciate ligament reconstruction (ACLR) is unclear. Thus, this study aimed to confirm the measurement properties of the RSI during SVCJs in athletes with ACLR at the phase of determining the timing of their return to sport.

METHODS

RSI during SVCJs and single-limb hop (single, triple, and crossover) tests were measured for post-ACLR and healthy athletes. The limb symmetry index (LSI) was calculated using the measurements of each parameter. For each test, patients were divided into two subgroups according to their LSI score (≥ 90%, satisfactory; < 90%, unsatisfactory). Fisher's exact test was used to examine the association of single-limb hop tests with RSI during the SVCJs.

RESULTS

A total of 21 post-ACLR and 17 healthy athletes completed all the tests. RSI during SVCJs was significantly lower on the involved limb than on the uninvolved limb in post-ACLR athletes (P < 0.001). The LSI of RSI during SVCJs of post-ACLR athletes was significantly lower than that of the healthy athletes (P < 0.01). Among the post-ACLR athletes, < 30% of those with LSIs > 90% in the single-limb hop tests had an LSI > 90% of the RSI during SVCJs.

CONCLUSIONS

RSI during SVCJs of post-ACLR athletes was significantly lower on the involved limb than on the uninvolved limb, and the asymmetry was more remarkable in the SVCJs than in the single-limb hop tests.

Beurteilung des neuromuskulären Funktionszustands bei Berufssportlern

In den letzten Jahren wurden bedeutende Fortschritte in den chirurgischen Techniken, der postoperativen Rehabilitation und der Identifizierung von Risikofaktoren für eine zweite Verletzung des vorderen Kreuzbands (VKB) gemacht. Dies führte jedoch nicht zu einer Verringerung des sekundären VKB-Verletzungsrisikos. Die Wiederherstellung der anatomischen (operative Rekonstruktion) und anschließend insbesondere der trainingsbedingten funktionellen Stabilität sollte eine grundlegende Voraussetzung für die Rückkehr zu Pivot-Sportarten nach einer VKB-Verletzung sein. Das VKB hat eine bedeutende Rolle bei der Kniepropriozeption mit der Konsequenz einer eingeschränkten sensomotorischen Regulation im Verletzungsfall. Das Perturbationstraining stellt eine große Herausforderung in der spätrehabilitativen Phase nach VKB-Rekonstruktion dar. Die Diagnostik der Muskelaktivierung im Rehabilitationsverlauf nach VKB-Rekonstruktion hat deshalb eine enorme Bedeutung. Mit der entwickelten Software können Charakteristika der motorischen Einheiten knieführender Muskeln zeitnah objektiviert und somit eine mögliche Überlastung bei hochreaktivem Perturbationstraining im Rahmen der spätrehabilitativen Phase nach VKB-Rekonstruktion vermieden werden.

Inter-limb asymmetry in youth elite soccer players: Effect of loading conditions

The presence of inter-limb asymmetries can influence strength performance and represent an injury risk factor for team sport athletes. The present study aimed to investigate the effects of changes in resistance loads using different assessment modalities on the magnitude and the direction of inter-limb asymmetry within the same leg. Fifteen young elite soccer players from the same professional academy performed rear-foot-elevated-split-squat-test at different loading conditions (body mass with no overload, 25% of body mass, 50% of body mass 50%), isokinetic knee flexor (concentric 30°·s^-1, concentric 60°·s^-1, eccentric 90°·s^-1) and extensor (concentric 60°·s^-1, eccentric 60°·s^-1). The outcomes from the agreement analyses suggested moderate level agreement between body mass vs body mass 25% (Kappa = 0.46), with no agreement or fair agreement for the other between-assessment comparison. Our results demonstrated that the magnitude and direction of within-limb strength imbalances were inconsistent when compared within the same assessment under different resistance load conditions.

Post-Operative Results of ACL Reconstruction Techniques on Single-Leg Hop Tests in Athletes: Hamstring Autograft vs. Hamstring Grafts Fixed Using Adjustable Cortical Suspension in Both the Femur and Tibia

Background and Objectives: Anterior cruciate ligament (ACL) tears are common injuries in the athletic population, and accordingly, ACL reconstruction (ACLR) is among the most common orthopedic surgical procedures performed in sports medicine. This study aims to compare the semitendinosus/gracilis (ST/G) and ACL hamstring grafts fixed using adjustable cortical suspension in both the femur and tibia (MAI) ACLR techniques. We aimed to compare the results of single-leg hop tests (SLHT) applied in different directions and limb symmetry indices (LSI) in athletes with a 6-month post-operative ACLR history. Materials and Methods: A retrospective cohort of 39 athletes from various sports branches who underwent MAI (n = 16) and ST/G (n = 23) ACLR techniques by the same surgeon were evaluated. The knee strength of the participants on the operated and non-operated sides was evaluated with five different SLHTs. The SLHT included the single hop for distance (SH), triple hop for distance (TH), crossover triple hop for distance (CH), medial side triple hop for distance (MSTH), and medial rotation (90°) hop for distance (MRH). Results: There was a significant improvement in the mean Lysholm, Tegner, and IKDC scores in the post-operative leg for both techniques (p < 0.05) compared to the pre-operative levels. When there was a difference between the SH of the operative and the non-operative legs in the ST/G technique (p < 0.05), there was no significant difference in the other hop distance for both ST/G and MAI (p > 0.05). There was no difference between the techniques regarding the LSI scores. Conclusions: The fact that our research revealed similar LSI rates of the SLHTs applied in different directions in the ST/G and MAI techniques assumes that the MAI technique can be an ACLR technique which can be functionally used in athletes.

Steadiness training improves the quadriceps strength and self-reported outcomes in persistent quadriceps weakness following nine months of anterior cruciate ligament reconstruction and failed conventional physiotherapy

Background Persistent quadriceps weakness may occur after anterior cruciate ligament reconstruction, limiting the strength gain. However, steadiness strengthening might change the inability to gain strength. Hence, we determined whether strength training with force steadiness and visual biofeedback can improve knee quadriceps torque, self-reported pain and knee stability in patients with persistent quadriceps weakness after knee anterior cruciate ligament reconstruction. Methods Twenty-five patients (aged 43.7 ± 12.2 years) with persistent quadriceps weakness following knee anterior cruciate ligament reconstruction and 34-weeks of physiotherapy performed unilateral strength training for both lower limbs. Four-weeks of conventional physiotherapy at week-30 were given, confirming the inability to gain torque. Then, steadiness training (isometric knee extension with visual biofeedback) was given for 7-weeks. Knee quadriceps peak torque, strength improvement, determination of responders to the intervention, coherence of strength gain between limbs, and self-reported outcomes (pain and knee stability) were obtained. Descriptive statistics and data inference using mixed-ANOVA, McNemar test, and χ² test were described. Findings Quadriceps torque in the reconstructed knee improved (98.2 ± 47.2-155.2 ± 78.9 Nm; p = 0.031) for most patients (84%). Nevertheless, the torque was lower than the healthy side maintaining asymmetry (155.2 ± 78.9 vs. 209.5 ± 101.8 Nm; p = 0.026). There was high (20%) and medium coherence (80%) between limbs. Knee stability and pain improved in 72% of the patients (p < 0.001). Interpretations Steadiness training after anterior cruciate ligament reconstruction followed 9 months of surgery and failed conventional physiotherapy, improves the persistent weakness and self-reported outcomes, but gain strength was dissimilar between limbs.

An Assessment of the Hopping Strategy and Inter-Limb Asymmetry during the Triple Hop Test: A Test–Retest Pilot Study

The aims of the present study are to: (1) determine within- and between-session reliability of multiple metrics obtained during the triple hop test; and (2) determine any systematic bias in both the test and inter-limb asymmetry scores for these metrics. Thirteen male young American football athletes performed three trials of a triple hop test on each leg on two separate occasions. In addition to the total distance hopped, manual detection of touch down and toe-off were calculated via video analysis, enabling flight time (for each hop), ground contact time (GCT), reactive strength index (RSI), and leg stiffness (between hops) to be calculated. Results showed all coefficient of variation (CV) values were ≤ 10.67% and intraclass correlation coefficients (ICC) ranged from moderate to excellent (0.53–0.95) in both test sessions. Intrarater reliability showed excellent reliability for all metrics (CV ≤ 3.60%, ICC ≥ 0.97). No systematic bias was evident between test sessions for raw test scores (g = −0.34 to 0.32) or the magnitude of asymmetry (g = −0.19 to 0.43). However, ‘real’ changes in asymmetry (i.e., greater than the CV in session 1) were evident on an individual level for all metrics. For the direction of asymmetry, kappa coefficients revealed poor-to-fair levels of agreement between test sessions for all metrics (K = −0.10 to 0.39), with the exception of the first hop (K = 0.69). These data show that, given the inherent limitations of distance jumped in the triple hop test, practitioners can confidently gather a range of reliable data when computed manually, provided sufficient test familiarization is conducted. In addition, although the magnitude of asymmetry appears to show only small changes between test sessions, limb dominance does appear to fluctuate between test sessions, highlighting the value of also monitoring the direction of the imbalance.

Deficit in knee extension strength following anterior cruciate ligament reconstruction is explained by a reduced neural drive to the vasti muscles

The persistence of quadriceps weakness represents a major concern following anterior cruciate ligament reconstruction (ACLR). The underlying adaptations occurring in the activity of spinal motoneurons are still unexplored. This study examined the discharge patterns of large populations of motor units (MUs) in the vastus lateralis (VL) and vastus medialis muscles following ACLR. Nine ACLR individuals and 10 controls performed unilateral trapezoidal contractions of the knee extensor muscles at 35%, 50% and 70% of the maximal voluntary isometric force (MVIF). High-density surface electromyography (HDsEMG) was used to record the myoelectrical activity of the vasti muscles in both limbs. HDsEMG signals were decomposed with a convolutive blind source separation method and MU properties were extracted and compared between sides and groups. The ACLR group showed a lower MVIF on the reconstructed side compared to the contralateral side (28.1%; P < 0.001). This force deficit was accompanied by reduced MU discharge rates (∼21%; P < 0.05), lower absolute MU recruitment and derecruitment thresholds (∼22% and ∼22.5%, respectively; P < 0.05) and lower input-output gain of motoneurons (27.3%; P = 0.009). Deficits in MU discharge rates of the VL and in absolute recruitment and derecruitment thresholds of both vasti MUs were associated with deficits in MVIF (P < 0.05). A strong between-side correlation was found for MU discharge rates of the VL of ACLR individuals (P < 0.01). There were no significant between-group differences (P > 0.05). These results indicate that mid- to long-term strength deficits following ACLR may be attributable to a reduced neural drive to vasti muscles, with potential changes in excitatory and inhibitory synaptic inputs. KEY POINTS: Impaired expression and control of knee extension forces is common after anterior cruciate ligament reconstruction and is related to high risk of a second injury. To provide novel insights into the neural basis of this impairment, the discharge patterns of motor units in the vastus lateralis and vastus medialis were investigated during voluntary force contractions. There was lower knee extensor strength on the reconstructed side with respect to the contralateral side, which was explained by deficits in motor unit discharge rate and an altered motoneuronal input-output gain. Insufficient excitatory inputs to motoneurons and increased inhibitory afferent signals potentially contributed to these alterations. These results further our understanding of the neural underpinnings of quadriceps weakness following anterior cruciate ligament reconstruction and can help to develop effective rehabilitation protocols to regain muscle strength and reduce the risk of a second injury.

Early knee status affects self-reported knee function 1 year after non-surgically treated anterior cruciate ligament injury

OBJECTIVES

The primary aim was to assess impact of early knee status on self-reported knee function at 3 and 12 months and on quadriceps strength at 12 months after non-surgically treated ACL injury. The secondary aim was to describe the recovery of muscle strength during the first year after the injury.

DESIGN

Prospective cohort study.

PARTICIPANTS

70 patients (42 males; mean age 27 ± 7 years) with acute ACL injury.

MAIN OUTCOME

Knee symptoms, knee function and sporting activities were assessed with the International Knee Documentation Committee Subjective Knee Form (IKDC-SKF). Muscle strength was assessed with an isokinetic dynamometer. Clinical assessment performed at baseline was used to evaluate early knee status.

RESULTS

Global knee function, knee joint stability during ADL, gait pattern and one-legged squat assessed in mean 2 weeks after injury hadimpact on self-reported knee function at 3 and 12 months (r² 0.105-0.267). Mean limb symmetry index (LSI) of muscle strength and jump performance were 91-98% at 12 months.

CONCLUSION

Early knee symptoms affect self-reported knee function at 3 and 12 months, while other factors are important for gaining muscle strength. Muscle strength recovered during the first year after ACL injury and reached mean LSI above 90%.

LEVEL OF EVIDENCE

Prospective cohort study, level II.

Test Batteries After Primary Anterior Cruciate Ligament Reconstruction: A Systematic Review

CONTEXT

There is a lack of consensus regarding test batteries for return to sport (RTS) after anterior cruciate ligament reconstruction (ACLR).

OBJECTIVE

To report the RTS test batteries for individuals after ACLR and to examine alignment with the American Academy of Orthopaedic Surgeons (AAOS) Appropriate Use Criteria (AUC). Finally, to examine how published RTS batteries prior to the AAOS AUC (2010-2015) compared with those after publication of the AUC (2016-2020).

DATA SOURCE

A systematic search of PubMed (2010-2020).

STUDY SELECTION

Studies were included if they were published from 2010 to 2020, patients underwent primary ACLR and were tested between 6 months and 2 years postoperatively and included a minimum of 2 assessments. Studies were excluded if patients were tested outside the designated time; had undergone a revision, contralateral, or multiligament injury; included healthy participants; were level 5 evidence or the study was a systematic review. A total of 1012 articles were reviewed and 63 met the criteria.

STUDY DESIGN

Systematic review.

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

Information regarding the RTS batteries and patient demographics were extracted from the included articles.

RESULTS

A total of 63 studies met the inclusion and exclusion criteria (22 from 2010-2015 and 41 from 2016-2020). The most common RTS batteries included the hop test, quadriceps strength test, and patient-reported outcome measures. No study met all 7 AUC; the most common criteria met were functional skills (98.4%), followed by confidence (22.2%), then range of motion and knee stability (20.6%).

CONCLUSION

The test batteries in the current literature show high variability and a lack of essential components necessary for RTS. No study met the AUC guidelines, suggesting a disconnect between recommended guidelines and clinical practice. Test battery research has expanded over the past decade; however, standardized, clinically applicable batteries that encompass all criteria are needed.

High rate of second ACL injury following ACL reconstruction in male professional footballers: an updated longitudinal analysis from 118 players in the UEFA Elite Club Injury Study

Background

Studies on subsequent anterior cruciate ligament (ACL) ruptures and career length in male professional football players after ACL reconstruction (ACLR) are scarce.

Aim

To investigate the second ACL injury rate, potential predictors of second ACL injury and the career length after ACLR.

Study design

Prospective cohort study.

Setting

Men’s professional football.

Methods

118 players with index ACL injury were tracked longitudinally for subsequent ACL injury and career length over 16.9 years. Multivariable Cox regression analysis with HR was carried out to study potential predictors for subsequent ACL injury.

Results

Median follow-up was 4.3 (IQR 4.6) years after ACLR. The second ACL injury rate after return to training (RTT) was 17.8% (n=21), with 9.3% (n=11) to the ipsilateral and 8.5% (n=10) to the contralateral knee. Significant predictors for second ACL injury were a non-contact index ACL injury (HR 7.16, 95% CI 1.63 to 31.22) and an isolated index ACL injury (HR 2.73, 95% CI 1.06 to 7.07). In total, 11 of 26 players (42%) with a non-contact isolated index ACL injury suffered a second ACL injury. RTT time was not an independent predictor of second ACL injury, even though there was a tendency for a risk reduction with longer time to RTT. Median career length after ACLR was 4.1 (IQR 4.0) years and 60% of players were still playing at preinjury level 5 years after ACLR.

Conclusions

Almost one out of five top-level professional male football players sustained a second ACL injury following ACLR and return to football, with a considerably increased risk for players with a non-contact or isolated index injury.

Recommendations for Movement Re-training After ACL Reconstruction

It is important to optimise the functional recovery process to enhance patient outcomes after major injury such as anterior cruciate ligament reconstruction (ACLR). Restoring movement quality during sporting-type movements is important prior to return-to-sport (RTS) after ACLR. Alterations in movement quality during an array of functional tasks are common amongst ACLR patients at or near the time of RTS and are associated with worse outcomes after ACLR. The inability to correct movement issues prior to RTS is likely due to the use of incomplete programmes or a lack of volume and intensity of movement re-training programmes. Although most clinicians and researchers understand that re-training movement after ACLR is important (e.g., the 'why'), there is often a disconnect with understanding the 'how' and 'what' of movement re-training post ACLR. The aim of this paper was to discuss factors relevant to movement dysfunction and re-training after ACLR and provide recommendations for clinicians to restore movement quality of patients after ACLR, prior to RTS. The paper recommends: (i) considering the factors which influence the expression of movement quality, which revolve around individual (e.g., neuromuscular, biomechanical, sensorimotor and neurocognitive factors), task-specific and environmental constraints; (ii) incorporating a three-staged movement re-training approach aligned to the ACLR functional recovery process: (1) addressing the neuromuscular and biomechanical and sensorimotor control factors which affect movement quality and motor learning, (2) including a progressive movement re-training approach to re-learn an array of functional tasks optimising coordination and motor learning (3) performing the final aspect of rehabilitation and movement training on the field, in realistic environments progressively simulating the sporting movement demands and environmental constraints; and (iii) effectively designing the movement programme for optimal load management, employing effective coach and feedback techniques and utilising qualitative movement analysis for transition between exercises, stages and for RTS.

Optimising the 'Mid-Stage' Training and Testing Process After ACL Reconstruction

Outcomes following anterior cruciate ligament (ACL) reconstruction need improving, with poor return-to-sport rates and high risk of secondary re-injury. There is a need to improve rehabilitation strategies after ACL reconstruction, if we can support enhanced patient outcomes. This paper discusses how to optimise the mid-stage rehabilitation process after ACL reconstruction. Mid-stage is a difficult and vitally important stage of the functional recovery process and provides the foundation on which to commence late-stage rehabilitation training. Often many aspects of mid-stage rehabilitation (e.g. knee extensors isolated muscle strength) are not actually restored prior to return-to-sport. In addition, if we are to allow time for optimal late-stage rehabilitation and return-to-sport training, we need to optimise the mid-stage rehabilitation approach and complete it in a timely manner. This paper forms a key part of a strategy to optimise the ACL rehabilitation approach and considers factors more specific to mid-stage rehabilitation characterised in 3 areas: (1) muscle strength: muscle and joint specific, in particular at the knee level, with the knee extensors and flexors and distally with the triceps surae and proximally with the lumbo-pelvic-hip complex, as well as closed kinetic chain strength; (2) altered basic motor patterning (movement quality) and (3) fitness re-conditioning. In addition, the paper provides recommendations on how to implement these into practice, discussing training planning and programming and suggests specific screening to monitor work and when the athlete is able to progress to the next stage (e.g. late-stage rehabilitation criteria).

RETURN TO PLAY AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

ABSTRACT The anterior cruciate ligament (ACL) tear represents more than half of all knee injuries in sports that involve body rotations and sudden changes of direction. Discharging the athlete for return to play (RTP) post-ACL reconstruction (ACLR) is a difficult task with multidisciplinary responsibility. For many years, a six-month period post-ACLR was adopted as the only criterion for RTP. However, it is now suggested that RTP should not be exclusively time-based, but to clinical data and systematic assessments. Despite the importance of post-ACLR factors for RTP, pre- and peri-ACLR factors must also be considered. Historically, ACLR is performed with the hamstring or autologous patellar tendons, although the choice of graft is still an open and constantly evolving theme. Anterolateral ligament reconstruction and repair of meniscal ramp tear associated with ACLR have recently been suggested as strategies for improving knee joint stability. Subjective questionnaires are easy to apply, and help identify physical or psychological factors that can hamper RTP. Functional tests, such as hop tests and strength assessment by means of isokinetic dynamometers, are fundamental tools for decision making when associated with clinical evaluation and magnetic resonance imaging. Recently, the capacity to generate force explosively has been incorporated into the muscle strength assessment. This is quantified through the rate of torque development (RTD). Due to characteristics inherent to the practice of sport, there is an extremely short time available for produce strength. Thus, RTD seems to better represent athletic demands than the maximum strength assessment alone. This review investigates the pre-, peri- and post-ACLR factors established in the literature, and shares our clinical practice, which we consider to be best practice for RTP. Level of evidence V; Specialist opinion.

Hop tests and psychological PROs provide a demanding and clinician-friendly RTS assessment of patients after ACL reconstruction, a registry study

Background

There is growing interest in assessing psychological well-being in patients after anterior cruciate ligament (ACL) reconstruction. It is unknown whether an assessment of psychological outcome in addition to tests of muscle function can facilitate decisions on return to sport (RTS). Therefore, the aim of this study was to evaluate passing rates in different physical RTS test batteries, with and without the inclusion of psychological outcome measures 1 year after ACL reconstruction.

Method

In this cross-sectional cohort study a total of 320 patients (51% men) aged 18–65 years were included 1 year after ACL reconstruction. Passing rates on different muscle function (MF) test batteries (with results presented as Limb Symmetry Index (LSI)), consisting of knee extension and flexion strength tests, 3 hop tests, and 2 psychological patient-reported outcomes (PROs); Quality of Life subscale from the Knee injury and Osteoarthritis Outcome Score (KOOS QoL) and ACL Return to Sport after Injury (ACL-RSI), were evaluated 1 year after ACL reconstruction. Muscle function test batteries comprised: 2 MF tests (vertical hop and hop for distance; pass = 90% LSI); 2 MF tests and 2 PRO (pass = 90% LSI, 62.5 points on KOOS QoL and 76.6 points on ACL-RSI), 5 MF tests (2 strength and 3 hop tests, pass = 90% LSI), and 5 MF tests and 2 PRO (pass = 90% LSI, 62.5 points on KOOS QoL and 76.6 points on ACL-RSI).

Results

Passing rates in the different test batteries were 47% for 2 MF tests, 19% for 2 MF tests and 2 PROs, 29% for 5 MF tests and 13% for 5 MF tests and 2 PROs. The use of psychological PROs together with tests of muscle function gave the lowest passing rate (13%). There was a very strong correlation between passing 2 hop tests and 2 PROs and passing 5 MF tests (rφ = 0.41) as well as passing 5 MF tests and 2 PROs (rφ = 0.79).

Conclusion

The use of hop tests together with psychological PROs provides a clinician-friendly RTS test battery for assessment 1 year after ACL reconstruction as the passing rate was 19% when using 2 hop-tests combined with 2 PROs, compared with 29% when using 5 tests of MF requiring advanced testing equipment.