Deficits in single-limb stance more than 20 years after ACL injury

Whole-body kinematics of squats two decades following anterior cruciate ligament injury

BACKGROUND

Kinematic studies suggest that injury of the anterior cruciate ligament (ACL) leads to long-lasting movement deficits or compensations to unload the injured knee. This study evaluated lower body kinematics during squats in individuals who suffered unilateral ACL-injury more than 20 years ago.

METHOD

Using motion capture, we compared maximum squat depth, time to complete the squat task, detailed kinematics, estimated kinetic-chain joint moments 0- 80° knee flexion, and weight distribution between legs across three groups with (ACLR, n = 27) and without ACL-reconstructive surgery (ACLPT, physiotherapy only, n = 28), and age-matched non-injured asymptomatic Controls (n = 31, average age across groups 47 years).

RESULTS

ACLPT demonstrated significantly reduced squat depth compared to Controls (p = 0.004), whereas ACLR performed similarly to Controls (p = 1.000). Other outcome variables were comparable between groups. All participants nevertheless demonstrated asymmetric weight distribution between legs but without systematic unloading of the injured side in the ACLgroups.

CONCLUSION

Expected compensatory strategies were not found in the ACL-groups, while poorer squat performance in the ACL-deficient group may depend on pure knee-joint mechanics, or lifestyle factors attributed to a less stable knee decades after ACL-injury.

Angle-specific torque profiles of concentric and eccentric thigh muscle strength 20 years after anterior cruciate ligament injury

Thigh muscle weakness prevails following anterior cruciate ligament (ACL) injury, as usually evaluated by peak concentric quadriceps strength. Assessment throughout the range of motion (ROM), and for antagonists may provide more comprehensive information. We evaluated angle-specific torque profiles and ratios of isokinetic thigh muscle strength in 70 individuals 23 ± 2 years post-ACL injury (44males, 46.9 ± 5.4 years); 33 treated with ACL-reconstruction (ACL-R), and 37 treated only with physiotherapy (ACL-PT), and 33 controls. Quadriceps and hamstrings torques for concentric/eccentric contractions (90°/s) and ratios between hamstrings/quadriceps strength (HQ) were compared between and within groups using inferential functional data methods. The injured ACL-R leg had lower concentric and eccentric quadriceps strength compared to non-injured leg throughout the ROM, and lower concentric (interval 70-79°) and eccentric (64-67°) quadriceps strength compared to controls. The injured ACL-PT leg showed lower eccentric quadriceps strength (53-77°) than non-injured leg and lower concentric (41-79°) and eccentric (52-81°) quadriceps and eccentric hamstrings (30-77°) strength than controls. There were no group differences for HQ-ratios. The injured ACL-R leg had higher HQ-ratio (34-37°) than non-injured leg. Angle-specific torque profiles revealed strength deficits, masked if using only peak values, and seem valuable for ACL-injury rehabilitation.

An obstacle clearance test for evaluating sensorimotor control after anterior cruciate ligament injury: A kinematic analysis

Sensorimotor deficits, particularly proprioceptive, are often reported following rupture of the anterior cruciate ligament (ACL). High secondary injury rates and long-term negative consequences suggest that these deficits are not properly identified using current assessment methods. We explored a novel obstacle clearance test to evaluate sensorimotor control in individuals following ACL reconstruction (ACLR) and rehabilitation. Thirty-seven post-ACLR individuals, 23 nonathletic asymptomatic controls (CTRL), and 18 elite athletes stepped over a hurdle-shaped obstacle, downward vision occluded, aiming for minimal clearance. Kinematic outcomes (3D motion capture) for the leading and trailing legs, for two unpredictably presented obstacle heights, were categorized into Accuracy: vertical foot clearance and minimal distance from the obstacle; Variability: end-point and hip/knee trajectory; and Symmetry: trunk/hip/knee crossing angles, hip-knee-ankle movement, and velocity curves. Accuracy was worse for CTRL compared with both other groups. ACLR had less leading and trailing vertical foot clearance with their injured compared with their noninjured leg. ACLR and athletes had less crossing knee flexion in their injured/nondominant legs compared with their contralateral leg, both leading and trailing. ACLR showed greater trunk flexion when crossing with their injured leg, both leading and trailing. For the leading leg, ACLR showed greater asymmetry for the hip-knee-ankle velocity curve compared with elite athletes. Trailing leg trajectory variability was lower for ACLR compared with CTRL and athletes for higher obstacles. Clinical significance: Sensorimotor deficits in individuals post-ACLR were reflected by greater asymmetry and less variable (more stereotypical) trajectories rather than limb positioning ability. This consideration should be addressed in clinical evaluations.

Muscle synergies for the control of single-limb stance with and without visual information in young individuals

Purpose

Single-limb stance is a demanding postural task featuring a high number of daily living and sporting activities. Thus, it is widely used for training and rehabilitation, as well as for balance assessment. Muscle activations around single joints have been previously described, however, it is not known which are the muscle synergies used to control posture and how they change between conditions of normal and lack of visual information.

Methods

Twenty-two healthy young participants were asked to perform a 30 s single-limb stance task in open-eyes and closed-eyes condition while standing on a force platform with the dominant limb. Muscle synergies were extracted from the electromyographical recordings of 13 muscles of the lower limb, hip, and back. The optimal number of synergies, together with the average recruitment level and balance control strategies were analyzed and compared between the open- and the closed-eyes condition.

Results

Four major muscle synergies, two ankle-dominant synergies, one knee-dominant synergy, and one hip/back-dominant synergy were found. No differences between open- and closed-eyes conditions were found for the recruitment level, except for the hip/back synergy, which significantly decreased (p = 0.02) in the closed-eyes compared to the open-eyes condition. A significant increase (p = 0.03) of the ankle balance strategy was found in the closed-eyes compared to the open-eyes condition.

Conclusion

In healthy young individuals, single-limb stance is featured by four major synergies, both in open- and closed-eyes condition. Future studies should investigate muscle synergies in participants with other age groups, as well as pathological conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-021-00392-z.

Retrospective experiences of individuals two decades after anterior cruciate ligament injury - a process of re-orientation towards acceptance

PURPOSE

Individual perspectives of long-term consequences decades after anterior cruciate ligament (ACL) injury are unexplored. We addressed experiences and the impact on life of former athletes >20 years post-ACL injury.

METHODS

Individual interviews, analysed using Grounded Theory, were conducted with 18 persons injured mainly during soccer 20-29 years ago.

RESULTS

A theoretical model was developed with the core category Re-orientation towards acceptance, overarching three categories illustrating the long-term process post-injury. Initially the persons felt like disaster had struck; their main recall was strong pain followed by reduced physical ability and fear of movement and re-injury. In the aftermaths of injury, no participant reached the pre-injury level of physical activity. Over the years, they struggled with difficult decisions, such as whether to partake or refrain from different physical activities, often ending-up being less physically active and thereby gaining body weight. Fear of pain and re-injury was however perceived mainly as psychological rather than resulting from physical limitations. Despite negative consequences and adjustments over the years, participants still found their present life situation manageable or even satisfying.

CONCLUSION

ACL injury rehabilitation should support coping strategies e.g., also related to fear of re-injury and desirable physical activity levels, also with increasing age.IMPLICATIONS FOR REHABILITATIONMore than 20 years after the ACL injury, the individuals despite re-orientation towards acceptance and a settlement with their life situation, still had fear of both pain and re-injury of the knee, with concerns about physical activity and gaining of body weight.Patients with ACL injury may need better individual guidance and health advice on how to remain physically active, to find suitable exercises and to maintain a healthy body weight.Education related to pain, treatment choices, physical activity, injury mechanisms in participatory discussions with the patient about the ACL injury may be beneficial early in the rehabilitation process to avoid catastrophizing and avoidance behaviour.ACL injury rehabilitation needs to address coping strategies incorporating the psychological aspects of suffering an ACL injury, including fear of movement/secondary injury, in order to support return-to-sport and/or re-orientation over time.

Effects of neuromuscular training on knee proprioception in individuals with anterior cruciate ligament injury: a systematic review and GRADE evidence synthesis

OBJECTIVE

To systematically review and summarise the evidence for the effects of neuromuscular training compared with any other therapy (conventional training/sham) on knee proprioception following anterior cruciate ligament (ACL) injury.

DESIGN

Systematic Review.

DATA SOURCES

PubMed, CINAHL, SPORTDiscus, AMED, Scopus and Physical Education Index were searched from inception to February 2020.

ELIGIBILITY CRITERIA

Randomised controlled trials (RCTs) and controlled clinical trials investigating the effects of neuromuscular training on knee-specific proprioception tests following a unilateral ACL injury were included.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently screened and extracted data and assessed risk of bias of the eligible studies using the Cochrane risk of bias 2 tool. Overall certainty in evidence was determined using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) tool.

RESULTS

Of 2706 articles retrieved, only 9 RCTs, comprising 327 individuals with an ACL reconstruction (ACLR), met the inclusion criteria. Neuromuscular training interventions varied across studies: whole body vibration therapy, Nintendo-Wii-Fit training, balance training, sport-specific exercises, backward walking, etc. Outcome measures included joint position sense (JPS; n=7), thresholds to detect passive motion (TTDPM; n=3) or quadriceps force control (QFC; n=1). Overall, between-group mean differences indicated inconsistent findings with an increase or decrease of errors associated with JPS by ≤2°, TTDPM by ≤1.5° and QFC by ≤6 Nm in the ACLR knee following neuromuscular training. Owing to serious concerns with three or more GRADE domains (risk of bias, inconsistency, indirectness or imprecision associated with the findings) for each outcome of interest across studies, the certainty of evidence was very low.

CONCLUSIONS

The heterogeneity of interventions, methodological limitations, inconsistency of effects (on JPS/TTDPM/QFC) preclude recommendation of one optimal neuromuscular training intervention for improving proprioception following ACL injury in clinical practice. There is a need for methodologically robust RCTs with homogenous populations with ACL injury (managed conservatively or with reconstruction), novel/well-designed neuromuscular training and valid proprioception assessments, which also seem to be lacking.

PROSPERO REGISTRATION NUMBER

CRD42018107349.

Curve analyses reveal altered knee, hip, and trunk kinematics during drop-jumps long after anterior cruciate ligament rupture

BACKGROUND

Anterior cruciate ligament (ACL) ruptures may lead to knee dysfunctions later in life. Single-leg tasks are often evaluated, but bilateral movements may also be compromised. Our aim was to use curve analyses to examine double-leg drop-jump kinematics in ACL-reconstructed, ACL-deficient, and healthy-knee cohorts.

METHODS

Subjects with unilateral ACL ruptures treated more than two decades ago (17-28years) conservatively with physiotherapy (ACL_PT, n=26) or in combination with reconstructive surgery (ACL_R, n=28) and healthy-knee controls (n=25) performed 40-cm drop-jumps. Three-dimensional knee, hip, and trunk kinematics were analyzed during Rebound, Flight, and Landing phases. Curves were time-normalized and compared between groups (injured and non-injured legs of ACL_PT and ACL_R vs. non-dominant and dominant legs of controls) and within groups (between legs) using functional analysis of variance methods.

RESULTS

Compared to controls, ACL groups exhibited less knee and hip flexion on both legs during Rebound and greater knee external rotation on their injured leg at the start of Rebound and Landing. ACL_R also showed less trunk flexion during Rebound. Between-leg differences were observed in ACL_R only, with the injured leg more internally rotated at the hip. Overall, kinematic curves were similar between ACL_R and ACL_PT. However, compared to controls, deviations spanned a greater proportion of the drop-jump movement at the hip in ACL_R and at the knee in ACL_PT.

CONCLUSIONS

Trunk and bilateral leg kinematics during double-leg drop-jumps are still compromised long after ACL-rupture care, independent of treatment. Curve analyses indicate the presence of distinct compensatory mechanisms in ACL_PT and ACL_R compared to controls.

A statistically compiled test battery for feasible evaluation of knee function after rupture of the Anterior Cruciate Ligament - derived from long-term follow-up data

Purpose

Clinical test batteries for evaluation of knee function after injury to the Anterior Cruciate Ligament (ACL) should be valid and feasible, while reliably capturing the outcome of rehabilitation. There is currently a lack of consensus as to which of the many available assessment tools for knee function that should be included. The present aim was to use a statistical approach to investigate the contribution of frequently used tests to avoid redundancy, and filter them down to a proposed comprehensive and yet feasible test battery for long-term evaluation after ACL injury.

Methods

In total 48 outcome variables related to knee function, all potentially relevant for a long-term follow-up, were included from a cross-sectional study where 70 ACL-injured (17–28 years post injury) individuals were compared to 33 controls. Cluster analysis and logistic regression were used to group variables and identify an optimal test battery, from which a summarized estimator of knee function representing various functional aspects was derived.

Results

As expected, several variables were strongly correlated, and the variables also fell into logical clusters with higher within-correlation (max ρ = 0.61) than between clusters (max ρ = 0.19). An extracted test battery with just four variables assessing one-leg balance, isokinetic knee extension strength and hop performance (one-leg hop, side hop) were mathematically combined to an estimator of knee function, which acceptably classified ACL-injured individuals and controls. This estimator, derived from objective measures, correlated significantly with self-reported function, e.g. Lysholm score (ρ = 0.66; p<0.001).

Conclusions

The proposed test battery, based on a solid statistical approach, includes assessments which are all clinically feasible, while also covering complementary aspects of knee function. Similar test batteries could be determined for earlier phases of ACL rehabilitation or to enable longitudinal monitoring. Such developments, established on a well-grounded consensus of measurements, would facilitate comparisons of studies and enable evidence-based rehabilitation.

Standing balance and inter-limb balance asymmetry at one year post primary anterior cruciate ligament reconstruction: Sex differences in a cohort study of 414 patients

BACKGROUND

Static standing balance can be safely assessed early following anterior cruciate ligament reconstruction (ACLR), and deficits may have important implications for long-term outcomes. This study includes a large cohort of people post-ACLR and has the primary aim of establishing whether inter-limb and sex differences exist, with a secondary aim of assessing the association between static balance variables and other outcome measures.

METHODS

A total of 414 patients with a primary ACLR performed a 30-s static single leg balance test. Centre of pressure (COP) path length, antero-posterior (AP) and medio-lateral (ML) sway range and slow and fast speed COP path-length were examined. Additional measures included single and triple hop distance and symmetry, knee flexion range of motion, ligament laxity and the International Knee Documentation Committee (IKDC) subjective knee evaluation form.

RESULTS

No significant inter-limb balance differences were present in females. Significant, yet small to negligible effect size (ES) differences were present in males for ML range (ES=0.19), and AP and ML axis slow speed path length (ES=0.11 and 0.23 respectively). Significant, negligible to moderate effect size (ES range=<0.01 to 0.60) sex differences were observed, with females showing reduced sway compared to males. No balance variables had associations with any other variable that were greater than weak.

DISCUSSION

Our findings provide evidence that primary ACLR does not appear to negatively impact single leg standing balance on the operated limb more than the non-operated side. The lack of association with other outcome measures warrants further longitudinal examination into the utility of static standing balance assessment.

Altered postural control strategies in quiet standing more than 20 years after rupture of the anterior cruciate ligament

AIM

To explore long-term consequences of anterior cruciate ligament (ACL) rupture on postural sway and control strategies during bilateral quiet standing, in subjects treated with or without reconstructive surgery compared to uninjured controls.

METHOD

70 individuals who had unilateral ACL rupture 23±2.4 years ago (33 received ACL reconstructive surgery, ACLR, and 37 had physiotherapy only, ACLPT) and 33 uninjured matched controls (CTRL) (mean age 46±5.3) stood quietly with eyes closed for 3min on a firm and on a compliant surface, respectively. Center of pressure (CoP) was registered with a force plate and postural sway was calculated from center of mass (CoM) derived from 3D kinematics. Sway density (SD) analyses of CoP assessed distance and duration of stable phases. The torque controlling postural sway was estimated from CoP-CoM.

RESULTS

Comparisons across conditions to CTRL revealed larger CoP-CoM-area in ACLR (p=0.017, CI: 10.95, 143.10), but not in ACLPT. Mean distance between SD-peaks was greater for ACLR (p<0.001, CI: 1.73, 5.31) than for ACLPT (p=0.006, CI: 0.56, 4.12) relative to CTRL. Duration of SD-peaks was smaller for both ACLR and ACLPT (p<0.001, CI: -4.04, -1.23 and -3.82, -1.03, respectively) compared to CTRL. CoM-area in the ACL-groups did not differ from CTRL.

CONCLUSIONS

ACL-injured subjects demonstrated greater postural control efforts than CTRL but without significant differences in postural sway. Control efforts were thus not directly associated with sway and further research should be focused on variance in postural control strategies.

One-leg hop kinematics 20 years following anterior cruciate ligament rupture: Data revisited using functional data analysis

BACKGROUND

Despite interventions, anterior cruciate ligament ruptures can cause long-term deficits. To assist in identifying and treating deficiencies, 3D-motion analysis is used for objectivizing data. Conventional statistics are commonly employed to analyze kinematics, reducing continuous data series to discrete variables. Conversely, functional data analysis considers the entire data series.

METHODS

Here, we employ functional data analysis to examine and compare the entire time-domain of knee-kinematic curves from one-leg hops between and within three groups. All subjects (n=95) were part of a long-term follow-up study involving anterior cruciate ligament ruptures treated ~20 years ago conservatively with physiotherapy only or with reconstructive surgery and physiotherapy, and matched knee-healthy controls.

FINDINGS

Between-group differences (injured leg, treated groups; non-dominant leg, controls) were identified during the take-off and landing phases, and in the sagittal (flexion/extension) rather than coronal (abduction/adduction) and transverse (internal/external) planes. Overall, surgical and control groups demonstrated comparable knee-kinematic curves. However, compared to controls, the physiotherapy-only group exhibited less flexion during the take-off (0-55% of the normalized phase) and landing (44-73%) phase. Between-leg differences were absent in controls and the surgically treated group, but observed during the flight (4-22%, injured leg>flexion) and the landing (57-85%, injured leg<internal rotation) phases in the physiotherapy-only group.

INTERPRETATION

Functional data analysis identified specific functional knee-joint deviations from controls persisting 20 years post anterior cruciate ligament rupture, especially when treated conservatively. This approach is suggested as a means for comprehensively analyzing complex movements, adding to previous analyses.

Postural sway in single-limb and bilateral quiet standing after unilateral total knee arthroplasty

AIM

To investigate whether total knee arthroplasty (TKA) was associated with stability in single-limb stance and whether reduced stability in single-limb stance was associated with increased postural sway in bilateral quiet standing.

METHODS

3D kinematics for center of mass was used to assess postural sway in 23 subjects with TKA and 23 controls. Tests included bilateral quiet standing with and without vision and on a compliant surface, and single-limb stance.

RESULTS

30% of the subjects in the TKA group were unable to maintain single-limb stance for 20s on any leg. Of the 70% in the TKA group able to stand on one leg, mean sway velocity in the medio-lateral direction was marginally higher for the prosthetic side (p=.02), but no differences were found between the TKA and the control group in single-limb stance. Performance in bilateral quiet standing was similar in TKA-subjects, able as well as unable to stand on one leg, and controls. Reduced quadriceps strength in the contralateral leg, higher BMI, and older age predicted failure to maintain single-limb stance.

CONCLUSION

In subjects able to stand on one leg, performance was considered comparable between the prosthetic and contralateral side and between groups. Inability to stand on one leg did not affect postural sway in bilateral quiet standing. The results suggest that inability to maintain single-limb stance is explained by reduced physical capacity rather than the knee condition in itself. The present study emphasizes the importance of physical activity to improve strength and functional capacity.