Corticomuscular cross-recurrence analysis reveals between-limb differences in motor control among individuals with ACL reconstruction.

Surgical reconstruction of the anterior cruciate ligament (ACL) and subsequent physical therapy can help athletes return to competition; however, re-injury rates remain disproportionately high due, in part, to lingering biomechanical and neurological factors that are not fully addressed during rehabilitation. Prior reports indicate that individuals exhibit altered electrical activity in both brain and muscle after ACL reconstruction (ACLR). In this investigation, we aimed to extend existing approaches by introducing a novel non-linear analysis of corticomuscular dynamics, which does not assume oscillatory coupling between brain and muscle: Corticomuscular cross-recurrence analysis (CM-cRQA). Our findings indicate that corticomuscular dynamics vary significantly between involved (injured) and uninvolved legs of participants with ACLR during voluntary isometric contractions between the brain and both the vastus medialis and lateralis. This finding points to a potential lingering neural deficit underlying re-injury for athletes after surgical reconstruction, namely the dynamical structure of neuromuscular (brain to quad muscle) coordination, which is significantly asymmetric, between limbs, in those who have ACLR.

Test-Retest Reliability and Visual Perturbation Performance Costs During 2 Reactive Agility Tasks.

CONTEXT: High secondary injury rates after orthopedic surgeries have motivated concern toward the construct validity of return-to-sport test batteries, as it is evident that common strength and functional assessments fail to elicit pertinent behaviors like visual search and reactive decision making. This study aimed to establish the test-retest reliability of 2 reactive agility tasks and evaluate the impact of visual perturbation on physical performance. METHODS: Fourteen physically active individuals completed 2 agility tasks with reaction time (ie, 4 corner agility), working memory, and pathfinding (ie, color recall) components. Participants completed both tasks 4 times in 2 sessions scheduled 7 days apart. Outcomes included performance metrics of reaction time, time to target, number of targets, and total time assessed with reactive training timing gates. To assess test-retest reliability, we used intraclass correlation coefficients (ICCs), standard error of measurement (SEM), and minimal detectable change (MDC). Stroboscopic goggles induced visual perturbation during the fourth trial of each task. To assess the effect of visual perturbation, we used paired t tests and calculated performance costs. RESULTS: The 4-corner agility task demonstrated excellent reliability with respect to reaction time (ICC3,1 = .907, SEM = 0.13, MDC = 0.35 s); time to light (ICC3,1 = .935, SEM = 0.07, MDC = 0.18 s); and number of lights (ICC3,1 = .800, SEM = 0.24, MDC = 0.66 lights). The color recall task demonstrated good-to-excellent test-retest reliability for time to lights (ICC3,1 = .818-.953, SEM = 0.07-0.27, MDC = 0.19-0.74 s); test time (ICC3,1 = .969, SEM = 5.43, MDC = 15.04 s); and errors (ICC3,1 = .882, SEM = 0.19, MDC = 0.53 errors). Visual perturbation resulted in increased time to target (P = .022-.011), number of targets (P = .039), and total test time (P = .013) representing moderate magnitude degradation of performance (d = 0.55-0.87, performance costs = 5%-12%). CONCLUSIONS: Both tasks demonstrated acceptable test-retest reliability. Performance degraded on both tasks with the presence of visual perturbation. These results suggest standardized reactive agility tasks are reliable and could be developed as components of dynamic RTS testing.

Somatosensory perturbations influence cortical activity associated with single-limb balance performance.

To determine the association between cortical activity and postural control performance changes with differing somatosensory perturbations. Healthy individuals (n = 15) performed a single-limb balance task under four conditions: baseline, unstable surface (foam), transcutaneous electrical nerve stimulation (TENS) applied to the stance-limb knee, and combined foam + TENS. Cortical activity was recorded with electroencephalography (EEG) and postural sway via triaxial force plate. EEG signals were decomposed, localized, and clustered to generate power spectral density in theta (4-7 Hz) and alpha-2 (10-12 Hz) frequency bands in anatomical clusters. Postural sway signals were analyzed with center of pressure (COP) sway metrics (e.g., area, distance, velocity). Foam increased theta power in the frontal and central clusters (d = 0.77 to 1.16), decreased alpha-2 power in bilateral motor, right parietal, and occipital clusters (d = - 0.89 to - 2.35) and increased sway area, distance, and velocity (d = 1.09-2.57) relative to baseline. Conversely, TENS decreased central theta power (d = - 0.60), but increased bilateral motor, left parietal, and occipital alpha-2 power (d = 0.51-1.40), with similar to baseline balance performance. In combination, foam + TENS attenuated sway velocity detriments and cortical activity caused by the foam condition alone. There were weak and moderate associations between percent increased central theta and occipital activity and increased sway velocity. Somatosensory perturbations changed patterns of cortical activity during a single-limb balance task in a manner suggestive of sensory re-weighting to pertinent sensory feedback. Across conditions decreased cortical activity in pre-motor and visual regions were associated with reduced sway velocity.

Neuromuscular function of the shoulder girdle and upper extremity musculature in individuals with a history of glenohumeral labral repair.

The purpose of this study was to compare neuromuscular function in the upper extremity musculature between individuals with glenohumeral labrum repair and uninjured controls. This cross-sectional study examined 16 individuals with a primary, unilateral glenohumeral labral repair (male/female: 13/3, age: 24.1 ± 5.0 years, time from surgery: 36.7 ± 33.3 months) and 14 uninjured individuals (male/female: 11/3, age: 23.8 ± 2.7 years) matched by age, sex, activity level, and limb dominance participated. Mass-normalized shoulder abduction and wrist flexion maximal voluntary isometric contraction (MVIC) torque, motoneuron pool excitability of the flexor carpi radialis (Hoffmann reflex), and corticospinal excitability of the upper trapezius, middle deltoid, and flexor carpi radialis (active motor threshold [AMT]) were evaluated. Dependent and independent t-tests were used to assess between-limb and between-group comparisons. Cohen's d effect sizes with 95% confidence intervals were used to quantify the magnitude of differences observed. Within the injured group, the involved limb had lesser shoulder abduction MVIC torque (p < 0.001, d = 1.16) and higher AMT for the upper trapezius (p = 0.01, d = 0.81) compared with the contralateral limb. The labral repair group had lesser shoulder abduction MVIC torque (p < 0.001, d = 1.17) and Hoffmann reflex (p = 0.01, d = 0.99), as well as higher AMT for the upper trapezius (p < 0.001, d = 1.23) in their involved limb compared with the control group. Large magnitude neuromuscular impairments are present beyond 6 months from glenohumeral labral repair, suggesting potential origins of impairments to be addressed during post-operative rehabilitation.

One size does not fit all: Influence of sex and maturation on temporal-spatial parameters for adolescent long-distance runners.

Runners and coaches are often interested in identifying the "ideal" running form to reduce the risk of injury and improve performance. While differences in pelvis and hip motion have been reported among adolescent female and male long-distance runners of different stages of physical maturation, the influence of sex and/or maturation on temporal-spatial parameters is unknown for adolescent runners. Adolescent runners of different stages of physical maturation (pre-, mid-, post-pubertal) completed an overground running analysis at a self-selected speed. We performed 2 × 3 ANCOVAs (covariate = running speed) to compare temporal-spatial parameters among sex and maturation groups. Pre-adolescents ran with higher cadences and shorter step lengths than mid- (p ≤ .01) and post-pubertal adolescents (p ≤ .01), respectively. Mid-pubertal males and post-pubertal females also ran with higher cadences and shorter step lengths than post-pubertal males (p ≤ .01). When step length was normalized to leg length, less physically mature runners demonstrated longer normalized step lengths (p ≤ .01). Caution is advised when using a "one-size-fits-all" approach for recommending an "ideal" cadence and/or step length for adolescent long-distance runners. A runner's sex, stage of physical maturation and leg length should be considered when assessing and prescribing cadence and/or step length.

Gluteal Central Activation in Females With Patellofemoral Pain: A Preliminary Study.

CONTEXT: Lesser hip muscle strength is commonly observed in females with patellofemoral pain (PFP) compared with females without PFP and is associated with poor subjective function and single-leg squat (SLS) biomechanics. Hip muscle weakness is theorized to be related to PFP, suggesting centrally mediated muscle inhibition may influence the observed weakness. The central activation ratio (CAR) is a common metric used to quantify muscle inhibition via burst superimposition. However, gluteal inhibition has yet to be evaluated using this approach in females with PFP. The study objectives are to (1) describe gluteal activation in the context of subjective function, hip strength, and squatting biomechanics and (2) examine the relationship of gluteal activation with subjective function and squatting biomechanics in females with PFP. DESIGN: Cross-sectional. METHODS: Seven females with PFP (age = 22.8 [3.6] y; mass = 69.4 [18.0] kg; height = 1.67 [0.05] m, duration of pain = 6-96 mo) completed this study. Subjective function was assessed with the Anterior Knee Pain Scale, while fear-avoidance beliefs were assessed with the Fear-Avoidance Belief Questionnaire physical activity and work subscales. Biomechanical function was assessed with peak hip and knee angles and moments in the sagittal and frontal planes during SLS. Gluteus medius (GMed) and gluteus maximus (GMax) activation were assessed with the CAR. Descriptive statistics were calculated, and relationships between variables were assessed with Spearman rho correlations. RESULTS: The CAR of GMed and GMax was 90.5% (8.1%) and 84.0% (6.3%), respectively. Lesser GMed CAR was strongly associated with greater hip adduction during SLS (ρ = -.775, P = .02) and greater fear-avoidance beliefs-physical activity subscale (ρ = -.764, P = .018). CONCLUSION: We found a wide range in GMed and GMax activation across females with PFP. Lesser GMed activation was associated with greater hip adduction during SLS and fear of physical activity, suggesting that gluteal inhibition should be assessed in patients with PFP.

Feasibility of Superimposed Neuromuscular Electrical Stimulation to the Gluteus Medius During a Resistance Training Program.

CONTEXT: Gluteus medius (GMed) weakness is a common impairment seen across multiple lower-extremity pathologies. Greater GMed weakness is moderately associated with greater frontal plane motion, often termed dynamic knee valgus during functional tasks which may increase risk of lower-extremity injury. Neuromuscular electrical stimulation (NMES) superimposed to targeted muscles has emerged in clinical practice; however, NMES superimposed to the GMed in unknown. It is essential to assess the safety, credibility, and expectancy of NMES superimposed to the GMed prior to implementation in clinical practice. The objective of this study was to evaluate feasibility, safety, credibility, and expectancy of improvement with a 2-week intervention with or without NMES to the GMed in females with dynamic knee valgus. DESIGN: Feasibility study. METHODS: A total of 22 adult females with dynamic knee valgus (age = 21.8 [1.4] y, mass = 76.9 [18.8] kg, height = 1.7 [0.1] m) completed a 2-week intervention with NMES or a sham treatment superimposed to the GMed during all therapeutic exercises. Feasibility was assessed by recruitment and completion rate, while safety was assessed by the total number of adverse events. Treatment credibility and expectancy was assessed with the Credibility Expectancy Questionnaire. Mixed-measure analysis of variance were used for statistical analysis (P ≤ .05). RESULTS: Recruitment was completed in 5 months with 100% completion rate and no adverse events. There was no difference in treatment credibility between groups (NMES = 23.7 [2.3], sham = 21.7 [3.4], P = .12); however, the NMES group demonstrated a greater expectancy score (NMES = 20.0 [3.8], sham = 15.9 [5.1], P = .045). CONCLUSION: Resistance training with NMES superimposed to the GMed is a feasible and safe intervention that resulted in greater expectance of success. Clinicians may consider superimposing NMES to the gluteal muscles when addressing muscle weakness in individuals with dynamic knee valgus.

Understanding Athletic Trainers' Knowledge, Intervention, and Barriers Toward Arthrogenic Muscle Inhibition.

CONTEXT: Arthrogenic muscle inhibition (AMI) is a common neurophysiological response to joint injury. While athletic trainers (ATs) are constantly treating patients with AMI, it is unclear how clinicians are using the available evidence to treat the condition. OBJECTIVE: To investigate ATs' general knowledge, clinical practice, and barriers for treating AMI. METHODS: A cross-sectional web-based survey was utilized. The survey was distributed to a random sample of 3000 ATs from the National Athletic Trainers' Association and through social media. 143 board certified ATs (age: 34.6 [10.3] y; experience: 11.7 [9.8] y) from various clinical settings and educational backgrounds were included in the analysis. RESULTS: One hundred one respondents were able to correctly identify the definition of AMI. The majority of these respondents correctly reported that joint effusion (n = 95, 94.1%) and abnormal activity from joint receptors (n = 91, 90.1%) resulted in AMI. Of the 101 respondents, only 58 (57.4%) reported using disinhibitory interventions to treat AMI. The most frequently used evidence supported interventions were transcutaneous electrical nerve stimulation (n = 38, 65.5%), neuromuscular electrical stimulation (n = 33, 56.9%), and focal joint cooling (n = 25, 43.1%). The interventions used correctly most often based on current evidence were neuromuscular electrical stimulation (n = 29/33, 87.9%) and transcutaneous electrical nerve stimulation (n = 26/38, 68.4%). Overall, difficulty quantifying AMI (n = 62, 61.24%) and lack of education (n = 71, 76.2%) were most frequently perceived as barriers. Respondents that did not use disinhibitory interventions perceived lack of experience treating AMI, understanding the terminology, and access to therapeutic modalities more often than the respondents that reported using disinhibitory interventions. CONCLUSION: Further education about concepts and treatment about AMI is warranted for ATs. Continued understanding of ATs' clinical practice in regard to AMI may help identify gaps in athletic training clinical education.

Influence of Patient Demographics and Surgical Characteristics on Pass Rates of Return-to-Activity Tests in Anterior Cruciate Ligament-Reconstructed Patients Before Physician Clearance.

OBJECTIVE: To identify the frequency of passing return-to-activity tests after anterior cruciate ligament reconstruction (ACLR) and to investigate the influence of patient-specific factors on pass rates. We hypothesized that isolated strength tests would be most difficult to pass and that graft type would be the most influential factor. DESIGN: Cross-sectional. SETTING: Laboratory. PARTICIPANTS: Eighty patients with a history of primary, unilateral ACLR, and 80 healthy controls participated. INTERVENTIONS: Bilateral isokinetic strength, isometric strength, and single-leg hop tests were recorded during a single visit. The International Knee Documentation Committee (IKDC) Subjective Knee Evaluation measured subjective knee function, and the Tegner Activity Scale measured physical activity level. MAIN OUTCOME MEASURES: Pass rates were calculated for 3 thresholds of absolute between-limb asymmetry: 0% to 10%, 11% to 15%, and 16% to 20%. Pass rates were compared by sex (male and female), graft type (patellar and hamstrings), meniscal procedure (yes and no), physical activity level (

Corticomotor function is associated with quadriceps rate of torque development in individuals with ACL surgery.

Impaired corticomotor function arising from altered intracortical and corticospinal pathways are theorized to impede muscle recovery following anterior cruciate ligament (ACL) surgery, yet functional implications of centrally driven adaptations remain unclear. We aimed to assess relationships between quadriceps corticomotor and neuromechanical function after ACL surgery, and to compare with contralateral and control limbs. 16 individuals after primary, unilateral ACL surgery and 16 sex- and age-matched controls participated. Corticomotor function was assessed using transcranial magnetic stimulation, and quantified via active motor thresholds (AMT), short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF). Neuromechanical function was quantified via electromechanical delay, early and late-phase rate of torque development (RTD0-50, RTD100-200), coefficient of variation, maximal voluntary isometric contraction (MVIC) torque, and central activation ratio. We observed significant correlations in the ACL limbs between: AMT and RTD0-50 (r = - 0.513, p = 0.031), SICI and RTD100-200 (r = 0.501, p = 0.048), AMT and SICI (r = - 0.659, p = 0.010), AMT and ICF (r = 0.579, p = 0.031), RTD0-50 and MVIC (r = 0.504, p = 0.023), and RTD100-200 and MVIC (r = 0.680, p = 0.002). The ACL limbs demonstrated higher AMT compared to controls (44.9 ± 8.4 vs. 30.1 ± 8.2%, p < 0.001), and lesser MVIC torque (2.37 ± 0.52 vs. 2.80 ± 0.59 Nm/kg, p = 0.005) and RTD100-200 (6.79 ± 1.72 vs. 7.90 ± 1.98 Nm/kg/s, p = 0.006) compared to the contralateral limbs. Our findings indicate that lesser corticospinal excitability is associated with lesser early-phase RTD, and greater intracortical inhibition is associated with lesser late-phase RTD. These findings provide evidence of implications of altered intracortical and corticospinal pathways relative to the ability to rapidly generate quadriceps torque following ACL surgery.

Corticospinal excitability can discriminate quadriceps strength indicative of knee function after ACL-reconstruction.

PURPOSE: To investigate relationships between quadriceps strength and neural activity, and to establish a clinical threshold of corticospinal excitability able to discriminate between patients with quadriceps strength indicative of satisfactory and unsatisfactory knee function after ACLR. METHODS: A total of 29 patients following primary, unilateral ACL-reconstruction (11 female, 23.2 ± 8.1 years of age, 7.3 ± 2.5 months since surgery) participated. Subjective knee function was quantified using the International Knee Documentation Committee (IKDC) subjective evaluation. Peak isokinetic knee extensor torque was assessed at 90°/s. Quadriceps corticospinal excitability was quantified via active motor threshold (AMT, %2-Tesla) using transcranial magnetic stimulation during a 5% maximal voluntary isometric contraction of the quadriceps. Pearson's r correlations were used to assess the relationship between peak knee extensor torque and AMT. Receiver operating characteristic (ROC) curves were used to establish a threshold of (a) mass-normalized peak knee extensor torque to discriminate satisfactory knee function (IKDC ≥ 75.9%), and (b) AMT to discriminate quadriceps strength indicative of satisfactory knee function. Likelihood ratios (LR) and the magnitude of change in pre-post-test probability were calculated for each threshold. RESULTS: Active motor threshold was negatively correlated with mass-normalized peak knee extensor torque (r = -0.503, P = 0.005). Knee extensor torque ≥1.23 Nm/kg was an excellent discriminator of satisfactory knee function (AUC = 0.890, P = 0.002; (+)LR = 9.56). An AMT ≤50.5% was an excellent discriminator of quadriceps strength indicative of satisfactory knee function following ACLR (AUC = 0.839, P = 0.005; (+)LR = 23.75). CONCLUSION: Lower corticospinal excitability was associated with lower quadriceps strength. An AMT above 50.5% was found to decrease the probability of having satisfactory knee strength by over 62%.

Quadriceps and Patient-Reported Function in ACL-Reconstructed Patients: A Principal Component Analysis.

CONTEXT: Assessment of physical function for individuals after anterior cruciate ligament reconstruction (ACL-R) is complex and warrants the use of diverse evaluation strategies. To maximize the efficiency of assessment, there is a need to identify tests that provide the most meaningful information about this population. OBJECTIVE: To investigate underlying constructs of quadriceps muscle function that uniquely describe aspects of performance in patients after ACL-R and establish clinical thresholds for measures able to classify patients with and without ACL-R. DESIGN: Cross-sectional. SETTING: Research laboratory. Patients (or Other Participants): Seventy-two patients with a primary, unilateral ACL-R (32 males and 40 females, age = 26.0 [9.3] y, time since surgery = 46.5 [58.0] mo) and 30 healthy controls (12 males and 18 females, age = 22.7 [4.6] y). INTERVENTION(S): Quadriceps function was assessed bilaterally during 1 study visit. MAIN OUTCOME MEASURES: Isokinetic strength (peak torque, total work, and average power) at 90° and 180°/s, maximal voluntary isometric contraction torque, fatigue index, central activation ratio, Hoffmann reflex, and active motor threshold. Principal component analyses were performed for the involved limb, contralateral limb, and limb symmetry. Receiver-operator characteristic curve analyses were conducted to determine the diagnostic utility of each variable. Binary logistic regression was used to predict group membership (ACL-R vs healthy). RESULTS: Three components of peripheral, central, and combined (peripheral and central) muscle function were identified, explaining 70.7% to 80.5% of variance among measures of quadriceps function. Total knee-extensor work at 90°/s (≥18.4 J/kg), active motor threshold (≥39.5%), and central activation ratio (≥94.7%) of the involved limb were strong predictors of patient status and correctly classified 83.5% of patients with ACL-R (P < .001). CONCLUSIONS: Unique constructs of peripheral, central, and combined muscle function exist in patients with ACL-R. Total knee-extensor work at 90°/s, active motor threshold, and central activation ratio consistently explained a significant portion of variance in measures of quadriceps function, demonstrated acceptable to excellent diagnostic utility, and predicted group membership with 72.8% to 83.5% accuracy.

Relationship Between Physical Therapy Characteristics, Surgical Procedure, and Clinical Outcomes in Patients After ACL Reconstruction.

CONTEXT: Postoperative rehabilitation is critical to optimize outcomes after anterior cruciate ligament reconstruction (ACLR). However, the relationship between physical therapy (PT) and clinical outcomes is unclear. OBJECTIVE: To describe PT characteristics following ACLR and to assess the relationships between PT characteristics, surgical procedure, and clinical outcomes. DESIGN: Cross-sectional. SETTING: Laboratory. Patients (or Other Participants): A total of 60 patients (31 females/29 males, age = 22.4 [9.2] y, height = 171.7 [9.9] cm, and mass = 70.2 [14.7] kg) with a history of primary unilateral ACLR (53.6% patellar tendon and 46.4% hamstring) participated. INTERVENTION(S): Patients completed a performance assessment and rated subjective knee function prior to physician clearance (mean = 6.3 [1.3] mo postoperatively) and were contacted within 6 months of clearance to complete a PT questionnaire. MAIN OUTCOME MEASURES: PT questionnaire item response, knee extension maximum voluntary isometric contraction (MVIC) torque, peak isokinetic knee extension torque, single leg hop distance, and International Knee Documentation Committee were measured. Correlations assessed relationships between PT quantity and clinical outcomes. Independent t tests compared PT quantity and clinical outcomes based on return-to-sport status, readiness to return to sport, and surgical procedure. RESULTS: Patients completed regular PT (2 d/wk, 25 wk, 58 visits) and were most likely to conclude when discharged by the therapist (68.3%). More than half (56.7%) returned to sport, yet most (73.3%) felt unready at discharge. Isokinetic torque was correlated with days of PT/week (r = .29, P = .03). Isokinetic torque and hop symmetry were reduced in patients who returned to sport (P < .05). Patients who felt ready to return completed fewer weeks of PT (P < .05). Patients with a patellar tendon graft completed more days of PT/week and total visits, but demonstrated lower MVIC torque, MVIC symmetry, and isokinetic symmetry (P < .05). CONCLUSIONS: Many patients felt unready to return to sport at PT discharge. PT frequency was associated with isokinetic torque, yet this relationship was small. Outcomes were reduced in patients who returned to sport, suggesting premature resumption of preinjury activity.

MRI-Based Assessment of Lower-Extremity Muscle Volumes in Patients Before and After ACL Reconstruction.

CONTEXT: Study of muscle volumes in patients after anterior cruciate ligament (ACL) injury and reconstruction (ACL-R) is largely limited to cross-sectional assessment of the thigh musculature, which may inadequately describe posttraumatic and postsurgical muscle function. No studies have prospectively examined the influence of ACL injury and reconstruction on lower-extremity muscle volumes. OBJECTIVE: Assess magnetic resonance imaging-derived lower-extremity muscle volumes, and quantify quadriceps strength and activation in patients following ACL injury and reconstruction. DESIGN: Prospective case series. SETTING: Research laboratory and magnetic resonance imaging facility. Patients (or Other Participants): Four patients (2 men and 2 women; age = 27.4 (7.4) y, height = 169.2 (8.1) cm, and mass = 74.3 (18.5) kg) scheduled for ACL-R. INTERVENTION(S): Thirty-five muscle volumes were obtained from a bilateral lower-extremity magnetic resonance imaging before and after ACL-R. MAIN OUTCOME MEASURES: Muscle volumes expressed relative to (1) a normative database presurgery and postsurgery, (2) limb symmetry presurgery and postsurgery, and (3) percentage change presurgery to postsurgery. Quadriceps function was quantified by normalized knee extension maximal voluntary isometric contraction torque and central activation ratio. RESULTS: Involved vastus lateralis and tibialis anterior were consistently smaller than healthy individuals (z < -1 SD) presurgery and postsurgery in all patients. Involved rectus femoris and vastus lateralis were more than 15% smaller than the contralateral limb presurgery, whereas the involved rectus femoris, gracilis, vastus medialis, vastus intermedius, and vastus lateralis muscle volumes exceeded 20% asymmetry postoperatively. Involved gracilis and semitendinosus atrophied more than 30% from presurgery to postsurgery. Involved maximal voluntary isometric contraction torque and central activation ratio increased by 12.7% and 12.5%, respectively, yet strength remained 33.2% asymmetric postsurgery. CONCLUSIONS: Adaptations in lower-extremity muscle volumes are present following ACL injury and reconstruction. Anterior thigh and shank muscles were smaller than healthy individuals, and large asymmetries in quadriceps volumes were observed presurgery and postsurgery. Selective atrophy of the semitendinosus and gracilis occurred following surgery. Volumetric deficits of the quadriceps musculature may exist despite improvements in muscle strength and activation.

Peroneal Nerve Dysfunction due to Multiligament Knee Injury: Patient Characteristics and Comparative Outcomes After Posterior Tibial Tendon Transfer.

OBJECTIVE: To objectively compare outcomes of nonoperative management and posterior tibial tendon (PTT) transfer for peroneal nerve injury due to multiligament knee injury (MLI). DESIGN: Retrospective cohort study with prospective follow-up. SETTING: Tertiary care institution. PATIENTS: Ten patients with peroneal nerve injury due to MLI (5 managed nonoperatively, 5 with PTT transfer) were evaluated and a control group of 4 patients without peroneal nerve injury. INTERVENTIONS: Clinical examination, subjective questionnaires, and 3-D motion capture gait analysis during flat-ground walking and stair descent. MAIN OUTCOME MEASURES: The primary outcome measure was the result of gait analysis. The results of subjective questionnaires were a secondary outcome measure. RESULTS: Dorsiflexion was significantly reduced at initial contact and mid-late swing phase in the nonoperative cohort. The PTT transfer cohort demonstrated increased dorsiflexion at each of these time intervals compared with patients managed nonoperatively, restoring symmetry between limbs. The PTT transfer cohort demonstrated similar gait patterns to controls but tended to be more everted. Ground reaction force was increased in the uninvolved limb in the PTT transfer group during gait and step down. There were no statistically significant differences in AOFAS, FAAM, IKDC, or Lysholm results. CONCLUSIONS: Posterior tibial tendon transfer is an option to restore dorsiflexion and eliminate the need for an orthosis in patients with foot drop due to MLI. Gait analysis demonstrates a significant improvement in sagittal plane ankle kinematics after PTT transfer. The trade-off is subtle instability, highlighting the dynamic stability that the PTT provides.

Immediate Effects of Therapeutic Ultrasound on Quadriceps Spinal Reflex Excitability in Patients With Knee Injury.

OBJECTIVE: To investigate the effects of nonthermal therapeutic ultrasound on quadriceps spinal reflex excitability in patients with knee joint injury. DESIGN: Double-blind, randomized controlled laboratory study with a pretest posttest design. SETTING: University laboratory. PARTICIPANTS: Recreationally active volunteers with a self-reported history of diagnosed intra-articular knee joint injury and documented quadriceps dysfunction (N=30). INTERVENTIONS: A nonthermal ultrasound, or sham, treatment was applied to the anteromedial knee. MAIN OUTCOME MEASURES: Hoffmann reflex measurements were recorded at baseline, immediately postintervention, and 20 minutes post-intervention. The peak Hoffmann reflex amplitude was normalized by the peak motor response (H/M ratio) measured from the vastus medialis using surface electromyography as an estimate of quadriceps motorneuron pool excitability. A repeated-measures analysis of variance was used for comparisons. RESULTS: A significant group-by-time interaction was observed for mean (P=.016) and change (P=.044) in H/M ratio. The ultrasound group demonstrated significantly higher mean (P=.015) and change (P=.028) in H/M ratio 20 minutes postintervention than did the sham ultrasound group. CONCLUSIONS: Quadriceps motoneuron pool excitability was facilitated 20 minutes after a nonthermal therapeutic ultrasound treatment, and not a sham treatment. These data provide supporting evidence of the contribution of peripheral receptors in modulation of the arthrogenic response in patients with persistent quadriceps dysfunction. Future research in this area should attempt to identify optimal treatment parameters and translate them to clinical outcomes.

Clinic- and laboratory-based measures of postural control in patellofemoral pain: A systematic review with meta-analysis and evidence gap map.

BACKGROUND: Patellofemoral pain (PFP) is a prevalent musculoskeletal disorder associated with functional impairments. Although postural control is commonly assessed in people with PFP, there are inconsistent results regarding potential postural control deficits in this population. RESEARCH QUESTION: This review aims to evaluate whether postural control is impaired in people with patellofemoral pain (PFP) and the effectiveness of interventions on postural control measures. METHODS: We searched six databases from their inception to May 5, 2023. We included studies assessing clinic- or laboratory-based postural control measures in people with PFP compared to pain-free controls, and intervention studies with PFP populations. We assessed risk of bias using the Joanna Briggs Institute critical appraisal checklists and the Cochrane Risk of Bias 2 tool. We assessed the certainty of evidence using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. We used random-effects meta-analyses considering subgroups based on type of task, measure, and intervention. RESULTS: Fifty-three studies were included. Very low certainty evidence indicated that people with PFP have shorter anterior (SMD = 0.53, 95 %CI:0.16,0.90), posteromedial (SMD = 0.54, 95 %CI:0.04,1.03) and posterolateral (SMD = 0.59, 95 %CI:0.11,1.07) reach distance, and worse composite score (SMD = 0.46, 95 %CI:0.22,0.70). Very low to moderate certainty evidence indicated that people with PFP have worse anterior-posterior and overall stability indexes during single-leg stance (SMD = -0.71, 95 %CI:-1.29,-0.14; SMD = -0.63, 95 %CI:-0.94,-0.32) and overall stability index during double-leg stance (SMD = -0.39, 95 %CI:-0.78,-0.00), but no differences in center of pressure area during stair ascent (SMD = 0.32, 95 %CI:-2.72, 3.36). Low certainty evidence indicated that kinesio taping improved anterior reach distance (SMD = -0.49, 95 %CI:-0.89,-0.09), while no significant differences were observed between pre- and post-intervention outcomes for conventional rehabilitation and rigid taping. SIGNIFICANCE: Clinicians should use clinic- (star excursion or Y-balance tests) and laboratory-based (stability indexes) measures to identify impairments of postural control in people with PFP. Low certainty of evidence suggests short-term improvement in postural control with kinesio taping.

Two-to-three times increase in natural hip and lumbar non-sagittal plane kinematics can lead to anterior cruciate ligament injury and cartilage failure scenarios during single-leg landings.

BACKGROUND: Analyzing sports injuries is essential to mitigate risk for injury, but inherently challenging using in vivo approaches. Computational modeling is a powerful engineering tool used to access biomechanical information on tissue failure that cannot be obtained otherwise using traditional motion capture techniques. METHODS: We extrapolated high-risk kinematics associated with ACL strain and cartilage load and stress from a previous motion analysis of 14 uninjured participants. Computational simulations were used to induce ACL failure strain and cartilage failure load, stress, and contact pressure in two age- and BMI-matched participants, one of each biological sex, during single-leg cross drop and single-leg drop tasks. The high-risk kinematics were exaggerated in 20% intervals, within their physiological range of motion, to determine if injury occurred in the models. Where injury occurred, we reported the kinematic profiles that led to tissue failure. FINDINGS: Our findings revealed ACL strains up to 9.99%, consistent with reported failure values in existing literature. Cartilage failure was observed in all eight analyzed conditions when increasing each high-risk kinematic parameter by 2.61 ± 0.67 times the participants' natural landing values. The kinematics associated with tissue failure included peak hip internal rotation of 22.48 ± 19.04°, peak hip abduction of 22.51 ± 9.09°, and peak lumbar rotation away from the stance limb of 11.56 ± 9.78°. INTERPRETATION: Our results support the ability of previously reported high-risk kinematics in the literature to induce injury and add to the literature by reporting extreme motion limits leading to injurious cases. Therefore, training programs able to modify these motions during single-leg landings may reduce the risk of ACL injury and cartilage trauma.

Single Leg Hop Performance After Anterior Cruciate Ligament Reconstruction: Ready for Landing but Cleared for Take-Off?

CONTEXT: While the landing phases of the single-leg hop for distance (SLHD) are commonly assessed, limited work reflects how the take-off phase influences hop performance in patients with anterior cruciate ligament reconstruction (ACLR). OBJECTIVE: To compare trunk and lower extremity biomechanics between individuals with ACLR and matched uninjured controls during take-off of the SLHD. DESIGN: Cross-sectional study design. SETTING: Laboratory setting. PATIENTS OR OTHER PARTICIPANTS: 16 individuals with ACLR and 18 uninjured controls. MAIN OUTCOME MEASURES: Normalized quadriceps isokinetic torque, hop distance, and respective limb symmetry indices (LSI) were collected for each participant. Sagittal and frontal kinematics and kinetics of the trunk, hip, knee, and ankle, as well as vertical and horizontal ground reaction forces (GRF) were recorded for loading and propulsion of the take-off phase of the SLHD. RESULTS: Those with ACLR had weaker quadriceps peak torque in the involved limb (p=0.001) and greater strength asymmetry (p<0.001) compared to controls. Normalized hop distance was not statistically different between limbs or between groups (p>0.05) and hop distance symmetry was not different between groups (p>0.05). During loading, the involved limb demonstrated lesser knee flexion angles (p=0.030) and knee power (p=0.007) compared to the uninvolved limb, and lesser knee extension moments compared to the uninvolved limb (p=0.001) and controls (p=0.005). During propulsion, the involved limb demonstrated lesser knee extension moment (p=0.027), knee power (p=0.010), knee (p=0.032) and ankle work (p=0.032), anterior- posterior GRF (p=0.047), and greater knee (p=0.016) abduction excursions compared to the uninvolved limb. CONCLUSIONS: Between-limb differences in SLHD take-off suggest a knee underloading strategy in the involved limb. These results provide further evidence that distance covered during SLHD assessment can overestimate function and fail to identify compensatory biomechanical strategies.

Reliability and validity of belt-stabilized and tension dynamometry for assessing hip strength and power in uninjured adults.

OBJECTIVES: To investigate the intra-rater reliability and validity of belt-stabilized and tension dynamometry to assess hip muscle strength and power. DESIGN: Repeated measures. SETTING: Biomechanics laboratory. PARTICIPANTS: Seventeen uninjured adults (age = 22.0 ± 2.3y; 13 females). MAIN OUTCOMES MEASURES: Peak torque (strength) and rate of torque development (RTD; power) were measured for hip abduction, internal rotation, external rotation and extension using an isokinetic dynamometer, and belt-stabilized and tension dynamometry. RESULTS: For peak torque assessment, belt-stabilized and tension dynamometry showed good (Intraclass Correlation Coefficient [ICC] = 0.848-0.899) and good-to-excellent (ICC = 0.848-0.942) reliability, respectively. For RTD, belt-stabilized dynamometry showed fair reliability for abduction (ICC = 0.524) and good reliability for hip internal rotation, external rotation, and extension (ICC = 0.702-0.899). Tension dynamometry showed good reliability for all motions when measuring RTD (ICC = 0.737-0.897). Compared to isokinetic dynamometry, belt-stabilized and tension dynamometry showed good-to-excellent correlations for peak torque assessment (r = 0.503-0.870), and fair-to-good correlations for RTD (r = 0.438-0.674). Bland-Altman analysis showed that measures from belt-stabilized and tension dynamometry had clinically meaningful disagreement with isokinetic dynamometry. CONCLUSION: Tension dynamometry is reliable for assessing hip strength and power in all assessed motions. Belt-stabilized dynamometry is reliable for assessing internal rotation, external rotation, and extension. Validity of both methods is questionable, considering the lack of agreement with isokinetic dynamometry.