Rotational 3D shear wave elasticity imaging: Effect of knee flexion on 3D shear wave propagation in in vivo vastus lateralis.

Skeletal muscle is a complex tissue, exhibiting not only direction-dependent material properties (commonly modeled as a transversely isotropic material), but also changes in observed material properties due to factors such as contraction and passive stretch. In this work, we evaluated the effect of muscle passive stretch on shear wave propagation along and across the muscle fibers using a rotational 3D shear wave elasticity imaging system and automatic analysis methods. We imaged the vastus lateralis of 10 healthy volunteers, modulating passive stretch by imaging at 8 different knee flexion angles (controlled by a BioDex system). In addition to demonstrating the ability of this acquisition and automatic processing system to estimate muscle shear moduli over a range of values, we evaluated potential higher order biomarkers for muscle health that capture the change in muscle stiffness along and across the fibers with changing knee flexion. The median within-subject variability of these biomarkers is found to be <16%, suggesting promise as a repeatable clinical metric. Additionally, we report an unexpected observation: that shear wave signal amplitude along the fibers increases with increasing flexion and muscle stiffness, which is not predicted by transversely isotropic (TI) material simulations. This observation may point to an additional potential biomarker for muscle health or inform other material modeling choices for muscle.

Do Climate and Environmental Characteristics Influence Concussion Incidence in Outdoor Contact Sports? A Systematic Review.

OBJECTIVE: To obtain a comprehensive understanding of the implications of environmental and climate factors on sport-related concussion incidence in outdoor contact sports. DATA SOURCES: MEDLINE (via Ovid), Embase (via Elsevier), CINAHL Complete (via EBSCOhost), SPORTDiscus (via EBSCOhost), and Scopus (via Elsevier). STUDY SELECTION: Studies that report incidence of sport-related concussion, assess data from athletes participating in outdoor contact sports, report on 1 or more climate or environmental factors, and report a diagnosis of concussion performed by a licensed medical professional were included. Reasons for exclusion included no report on extrinsic or environmental factors, no data on sport-related concussion incidence, and self-report of concussion diagnosis. DATA EXTRACTION: This systematic review was conducted using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines using 2 reviewers at each phase and a third reviewer for conflict resolution. DATA SYNTHESIS: A total of 7558 articles were reviewed, and 20 met the inclusion criteria. There was moderate to strong strength of evidence concluding no difference between surface type (grass versus artificial) on sport-related concussion risk. Moderate to strong strength of evidence was found supporting no difference in sport-related concussion incidence based on game location (home versus away). There was no consensus on the effects of altitude or temperature on sport-related concussion incidence. One high-quality study found a decreased risk of sport-related concussion when playing in wet versus dry conditions. Heterogenous populations and data collection methods prevented extraction and meta-analysis. CONCLUSIONS: Although a consensus on specific environmental and climate factors that influence sport-related concussion incidence was limited, the majority of studies were of high quality and gave insight into opportunities for future investigation. Administrators of large injury surveillance databases should consider including specific environmental and climate factors to provide investigators with robust data sets to better understand potential associations with sport-related concussion.

Repeatability of Rotational 3-D Shear Wave Elasticity Imaging Measurements in Skeletal Muscle.

Shear wave elasticity imaging (SWEI) usually assumes an isotropic material; however, skeletal muscle is typically modeled as a transversely isotropic material with independent shear wave speeds in the directions along and across the muscle fibers. To capture these direction-dependent properties, we implemented a rotational 3-D SWEI system that measures the shear wave speed both along and across the fibers in a single 3-D acquisition, with automatic detection of the muscle fiber orientation. We tested and examined the repeatability of this system's measurements in the vastus lateralis of 10 healthy volunteers. The average coefficient of variation of the measurements from this 3-D SWEI system was 5.3% along the fibers and 8.1% across the fibers. When compared with estimated respective 2-D SWEI values of 16.0% and 83.4%, these results suggest using 3-D SWEI has the potential to improve the precision of SWEI measurements in muscle. Additionally, we observed no significant difference in shear wave speed between the dominant and non-dominant legs along (p = 0.26) or across (p = 0.65) the muscle fibers.

Parametric Analysis of SV Mode Shear Waves in Transversely Isotropic Materials Using Ultrasonic Rotational 3-D SWEI.

Ultrasonic rotational 3-D shear wave elasticity imaging (SWEI) has been used to induce and evaluate multiple shear wave modes, including both the shear horizontal (SH) and shear vertical (SV) modes in in vivo muscle. Observations of both the SH and SV modes allow the muscle to be characterized as an elastic, incompressible, transversely isotropic (ITI) material with three parameters: the longitudinal shear modulus µL , the transverse shear modulus µT , and the tensile anisotropy χE . Measurement of the SV wave is necessary to characterize χE , but the factors that influence SV mode generation and characterization with ultrasonic SWEI are complicated. This work uses Green's function (GF) simulations to perform a parametric analysis to determine the optimal interrogation parameters to facilitate visualization and quantification of SV mode shear waves in muscle. We evaluate the impact of five factors: µL , µT , χE , fiber tilt angle [Formula: see text], and F-number of the push geometry on SV mode speed, amplitude, and rotational distribution. These analyses demonstrate that the following hold: 1) as µL increases, SV waves decrease in amplitude so are more difficult to measure in SWEI imaging; 2) as µT increases, the SV wave speeds increase; 3) as χE increases, the SV waves increase in speed and separate from the SH waves; 4) as fiber tilt angle [Formula: see text] increases, the measurable SV waves remain approximately the same speed, but change in strength and in rotational distribution; and 5) as the push beam geometry changes with F-number, the measurable SV waves remain approximately the same speed, but change in strength and rotational distribution. While specific SV mode speeds depend on the combinations of all parameters considered, measurable SV waves can be generated and characterized across the range of parameters considered. To maximize measurable SV waves separate from the SH waves, it is recommended to use an F/1 push geometry and [Formula: see text].

Association of Jump-Landing Biomechanics With Tibiofemoral Articular Cartilage Composition 12 Months After ACL Reconstruction.

BACKGROUND: Excessively high joint loading during dynamic movements may negatively influence articular cartilage health and contribute to the development of posttraumatic osteoarthritis after anterior cruciate ligament reconstruction (ACLR). Little is known regarding the link between aberrant jump-landing biomechanics and articular cartilage health after ACLR. PURPOSE/HYPOTHESIS: The purpose of this study was to determine the associations between jump-landing biomechanics and tibiofemoral articular cartilage composition measured using T1ρ magnetic resonance imaging (MRI) relaxation times 12 months postoperatively. We hypothesized that individuals who demonstrate alterations in jump-landing biomechanics, commonly observed after ACLR, would have longer T1ρ MRI relaxation times (longer T1ρ relaxation times associated with less proteoglycan density). STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A total of 27 individuals with unilateral ACLR participated in this cross-sectional study. Jump-landing biomechanics (peak vertical ground-reaction force [vGRF], peak internal knee extension moment [KEM], peak internal knee adduction moment [KAM]) and T1ρ MRI were collected 12 months postoperatively. Mean T1ρ relaxation times for the entire weightbearing medial femoral condyle, lateral femoral condyle (global LFC), medial tibial condyle, and lateral tibial condyle (global LTC) were calculated bilaterally. Global regions of interest were further subsectioned into posterior, central, and anterior regions of interest. All T1ρ relaxation times in the ACLR limb were normalized to the uninjured contralateral limb. Linear regressions were used to determine associations between T1ρ relaxation times and biomechanics after accounting for meniscal/chondral injury. RESULTS: Lower ACLR limb KEM was associated with longer T1ρ relaxation times for the global LTC (ΔR 2 = 0.24; P = .02), posterior LTC (ΔR 2 = 0.21; P = .03), and anterior LTC (ΔR 2 = 0.18; P = .04). Greater ACLR limb peak vGRF was associated with longer T1ρ relaxation times for the global LFC (ΔR 2 = 0.20; P = .02) and central LFC (ΔR 2 = 0.15; P = .05). Peak KAM was not associated with T1ρ outcomes. CONCLUSION: At 12 months postoperatively, lower peak KEM and greater peak vGRF during jump landing were related to longer T1ρ relaxation times, suggesting worse articular cartilage composition.

Establishing Age- and Sex-Specific Norms for Pediatric Return-to-Sports Physical Performance Testing.

BACKGROUND: Graft tears and contralateral anterior cruciate ligament (ACL) tears are common in pediatric athletes after ACL reconstruction. Use of objective return-to-sports (RTS) criteria, in particular physical performance tests (PPTs), is believed to reduce the incidence of secondary injury; however, pediatric norms for these tests are unknown. PURPOSE: To establish a proof of concept for the creation of age- and sex-based norms for commonly used RTS PPTs in healthy pediatric athletes, allowing the creation of growth curves for clinical referencing. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A total of 100 healthy people who were between the ages of 6 and 18 years and involved in organized sports were enrolled, with even distributions of age and sex. All participants underwent 9 common RTS PPTs: stork test, stork test on Bosu, single-leg squat, single-leg squat on Bosu, clockwise and counterclockwise quadrant hops, single-leg hop for distance, 6-m timed hop, and triple crossover hop for distance. Mean performance across limbs was calculated for each individual. Chronological age, height, weight, sex, and self-reported Pubertal Maturational Observational Scale (PMOS) score were recorded. Univariable and multivariable models were created for each PPT, assessing the importance of the recorded descriptive variables. Quantile regression was used to create growth curves for each PPT. RESULTS: The cohort was 52% female, and the mean ± standard deviation age was 11.7 ± 3.6 years. PMOS was highly correlated with age (r = 0.86) and was excluded from the regressions. In univariable regression, age, height, and weight were strong predictors of performance for all PPTs, whereas sex was a predictor of performance on the single-leg and triple crossover hops for distance (with males outperforming females). Height and weight were excluded from multivariable regression because of multicollinearity with age. Multivariable regression showed predictive patterns for age and sex that were identical to those shown in the univariable analysis. Given ceiling effects, quantile regression for the stork tests was not possible, but quantile regression growth curves were successfully created for the 7 remaining PPTs. CONCLUSION: Chronological age and sex accurately predicted performance on common RTS PPTs in pediatric patients. The growth curves presented herein could assist clinicians with benchmarking pediatric patients postoperatively against a healthy athletic cohort.

Identifying achilles tendon structure differences by ultrasound tissue characterization in asymptomatic individuals.

Ultrasound Tissue Characterization (UTC) is a modality that can be utilized to characterize tendon tissue structure using ultrasonographic imaging paired with a computer algorithm to distinguish echo-types. Several studies have demonstrated UTCs ability to distinguish Achilles tendon morphology changes, but no study has established normative data of the Achilles tendon in the general population. The aim of this study was to determine UTC echo-type distribution in the Achilles tendon in an asymptomatic population. UTC scans were completed and analyzed on 508 participants without Achilles tendinopathy. Dedicated UTC-algorithms were used to distinguish and calculate echo-type percentages and the fiber type distribution was compared. The overall sample echo-type percentages demonstrated greater levels of Type I and II echo-types, 65.73% and 32.00%, respectively, and lower levels of Type III and IV echo-types, 1.74% and 0.57%, respectively. In addition, females had lower levels of Echo-type I compared to men and greater levels of echo-type II (p < 0.001). We also found that African-Americans had significantly greater amounts of echo-type I and lesser amounts of echo-type II when compared to Caucasians (p < 0.05). The results of this study create a normative data set for future UTC studies to utilize as a baseline for the evaluation of Achilles tendons. In addition, it demonstrated tendon type differences between sexes and races that need to be accounted for in future studies.

Differences in Biomechanical Loading Magnitude During a Landing Task in Male Athletes with and without Patellar Tendinopathy.

CONTEXT: Prior research has not established if overloading or underloading movement profiles are present in symptomatic and asymptomatic athletes with patellar tendon structural abnormality (PTA) compared to healthy athletes. OBJECTIVE: The purpose was to compare involved limb landing biomechanics between male athletes with and without patellar tendinopathy. DESIGN: Cross-sectional study Setting: Laboratory Patients or Other Participants: 43 males were grouped based on patellar tendon pain & ultrasound imaging of the proximal patellar tendon: symptomatic with PTA (SYM-PTA; n=13; 20±2yrs; 1.8±0.1m; 84±5kg), asymptomatic with PTA (ASYM-PTA; n=15; 21±2yrs; 1.8±0.1m; 82±13kg), and healthy control (CON; n=15; 20±2yrs; 1.8±0.1m; 79±12kg). MAIN OUTCOME MEASURES: 3D biomechanics were collected during double-limb jump-landing. Kinematic (knee flexion angle (KF)) and kinetic (vertical ground reaction force (VGRF); internal knee extension moment (KEM); patellar tendon force (FPT)) variables were analyzed as continuous waveforms during the stance phase for the involved limb. Mean values were calculated for each 1% of stance, normalized over 202 data points (0-100%), and plotted with 95% confidence intervals. Statistical significance was defined as a lack of 95% CI overlap for ≥ 6 consecutive data points. RESULTS: SYM-PTA had lesser KF than CON throughout the stance phase. ASYM-PTA had lesser KF than CON in the early and late stance phase. SYM-PTA group had lesser KEM and FPT than CON in early stance, as well as ASYM-PTA in mid-stance. CONCLUSIONS: Male athletes with SYM-PTA demonstrated a patellar tendon load-avoidance profile compared to ASYM-PTA and CON athletes. ASYM-PTA did not show evidence of overloading compared to CON. Our findings support the need for individualized treatments for athletes with tendinopathy to maximize load-capacity. TRIAL REGISTRY: ClinicalTrials.gov (#XXX).

Changes in Infrapatellar Fat Pad Volume 6 to 12 Months After Anterior Cruciate Ligament Reconstruction and Associations With Patient-Reported Knee Function.

CONTEXT: Hypertrophy of the infrapatellar fat pad (IFP) in idiopathic knee osteoarthritis has been linked to deleterious synovial changes and joint pain related to mechanical tissue impingement. Yet little is known regarding the IFP's volumetric changes after anterior cruciate ligament reconstruction (ACLR). OBJECTIVES: To examine changes in IFP volume between 6 and 12 months after ACLR and determine associations between patient-reported outcomes and IFP volume at each time point as well as the volume change over time. In a subset of individuals, we examined interlimb IFP volume differences 12 months post-ACLR. STUDY DESIGN: Prospective cohort study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: We studied 26 participants (13 women, 13 men, age = 21.88 ± 3.58 years, body mass index = 23.82 ± 2.21 kg/m2) for our primary aims and 13 of those participants (8 women, 5 men, age = 21.15 ± 3.85 years, body mass index = 23.01 ± 2.01 kg/m2) for our exploratory aim. MAIN OUTCOME MEASURE(S): Using magnetic resonance imaging, we evaluated the IFP volume change between 6 and 12 months post-ACLR in the ACLR limb and between-limbs differences at 12 months in a subset of participants. International Knee Documentation Committee subjective knee evaluation (IKDC) scores were collected at 6-month and 12-month follow-ups, and associations between IFP volume and patient-reported outcomes were determined. RESULTS: The IFP volume in the ACLR limb increased from 6 months (19.67 ± 6.30 cm3) to 12 months (21.26 ± 6.91 cm3) post-ACLR. Greater increases of IFP volume between 6 and 12 months were significantly associated with better 6-month IKDC scores (r = .44, P = .03). The IFP volume was greater in the uninjured limb (22.71 ± 7.87 cm3) than in the ACLR limb (20.75 ± 9.03 cm3) 12 months post-ACLR. CONCLUSIONS: The IFP volume increased between 6 and 12 months post-ACLR; however, the IFP volume of the ACLR limb remained smaller than that of the uninjured limb at 12 months. In addition, those with better knee function 6 months post-ACLR demonstrated greater increases in IFP volume between 6 and 12 months post-ACLR. This suggests that greater IFP volumes may play a role in long-term joint health after ACLR.

Healthy Pediatric Athletes Have Significant Baseline Limb Asymmetries on Common Return-to-Sport Physical Performance Tests.

BACKGROUND: Return to sport (RTS) after anterior cruciate ligament (ACL) reconstruction in children is associated with a much higher risk (∼30%) of subsequent ACL injury than in adults. Most RTS testing protocols use a limb symmetry index (LSI) ≥90% on physical performance tests (PPTs) to assess an athlete's readiness for sport. This assumes that, in a healthy state, the physical performances across both lower extremities are and should be equal. PURPOSE: To determine the prevalence of limb asymmetries >10% in the uninjured pediatric population on common PPTs as well as to explore the relationship between athlete variables, limb preference, and LSI values. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: This study included healthy volunteers (N = 100) evenly distributed between the ages of 6 and 18 years (mean age, 11.7 ± 3.6 years; 52% female). Participants performed 9 common PPTs. For analysis, we developed a composite score for each limb by averaging trials. We then calculated the LSI for each test. Univariable and multivariable linear regression analyses were performed to assess the relationship between athlete variables (age, sex, height, and weight) and LSI for each PPT. RESULTS: Instances of poor baseline limb symmetry (<90% LSI) were common across all PPTs. The single-leg timed hop had the highest percentage of participants, with LSI ≥90% at 73%, while the stork on a Bosu ball had the lowest percentage at 23%. After adjusting for age, female sex showed a significant association with LSI for the stork test (P = .010) and the quadrant hop-counterclockwise (P = .021). Additionally, after adjusting for sex, increasing age showed a significant association with LSI for the stork test (P < .001), single-leg squat on a Bosu ball (P = .010), quadrant hop-clockwise (P = .016), and quadrant hop-counterclockwise (P = .009). CONCLUSION: The majority of healthy athletes 18 years and younger demonstrated significant (<90%) limb asymmetries. Limb symmetry was not consistently affected by participant age or sex, and the effect sizes of these relationships were small. These findings should encourage clinicians and coaches to exercise caution in using the LSI as an isolated measure of RTS readiness after injury in pediatric athletes.

Landing biomechanics are not immediately altered by a single-dose patellar tendon isometric exercise protocol in male athletes with patellar tendinopathy: A single-blinded randomized cross-over trial.

OBJECTIVES: To a) determine the acute effects of a single-dose patellar tendon isometric exercise protocol on involved limb landing biomechanics in individuals with patellar tendinopathy and asymptomatic patellar tendon pathology, and b) determine if individuals with patellar tendinopathy demonstrated changes in pain following a single-dose patellar tendon isometric exercise protocol. DESIGN: Single-blinded randomized cross-over trial. SETTING: Laboratory; PARTICIPANTS: 28 young male athletes with symptomatic (n = 13, age: 19.62 ± 1.61) and asymptomatic (n = 15, age: 21.13 ± 1.88) patellar tendinopathy. MAIN OUTCOME MEASURES: Participants completed a single-dose patellar tendon isometric exercise protocol and a sham-TENS protocol, randomized and separated by 7-10 days. Pain-levels during a single-limb decline squat (SLDS) and three-dimensional biomechanics were collected during a double-limb jump-landing task before and after each intervention protocol. A mixed-model repeated measures ANOVA was conducted to compare change scores for all dependent variables. RESULTS: There were no group × intervention interactions for change in pain (F(1, 26) = 0.555, p = 0.463). There was one significant group × intervention interaction for vertical ground reaction force (VGRF) (F(1, 26) = 5.33, p = 0.029). However, post-hoc testing with Bonferroni correction demonstrated no statistical significance for group (SYM: t = -1.679, p = 0.119; ASYM: t = -1.7, p = 0.107) or intervention condition (isometric: t = -2.58, p = 0.016; sham-TENS: 0.72, p = 0.460). There were no further significant group × intervention interactions (p > 0.05). CONCLUSIONS: A single-dose patellar tendon isometric exercise protocol did not have acute effects on landing biomechanics or pain levels in male athletes with patellar tendinopathy or asymptomatic patellar tendon pathology.

Development of Concise Physical Performance Test Batteries in Young Athletes.

PURPOSE: This study aimed 1) to define the principal components of physical function assessed by 10 common lower extremity physical performance tests and 2) to derive a reduced-item set of physical performance tests that efficiently and accurately measures raw performance and limb symmetry on each underlying component in pediatric and adolescent athletes. METHODS: This study included healthy, uninjured volunteers (n = 100) between the ages 6 and 18 yr (mean age = 11.7 ± 3.6 yr; 52 females). Subjects performed the stork balance, stork balance on BOSU® Balance Trainer, single leg squat (SLS), SLS on BOSU, clockwise and counterclockwise quadrant single leg hop (SLH), forward SLH, timed SLH, triple crossover SLH, and lower quarter Y-Balance Test™. Item reduction was performed using principal components analysis (PCA). We developed separate principal components analysis for average raw performance and side-to-side limb symmetry, with secondary analyses to evaluate consistency of results by age and sex. RESULTS: We identified two components for average raw performance (accounting for 65.2% of the variance in total test battery) with a reduced-item set composed of five tests, and four components for limb symmetry (accounting for 62.9% of the variance in total test battery) with a reduced-item set of seven tests. The most parsimonious test suitable for screening both average raw performance and limb symmetry would consist of five tests (stork balance on BOSU, SLS on BOSU, forward SLH, timed SLH, and lower quarter Y-Balance Test™). Age- and sex-specific test batteries may be warranted. CONCLUSION: Comprehensive screening for lower extremity average raw performance and limb symmetry is possible with short physical performance test batteries.

Landing Biomechanics, But Not Physical Activity, Differ in Young Male Athletes With and Without Patellar Tendinopathy.

OBJECTIVE: To examine differences in biomechanical and physical activity load in young male athletes with and without patellar tendinopathy. DESIGN: Cross-sectional cohort study. METHODS: Forty-one young male athletes (15-28 years of age) were categorized into 3 distinct groups: symptomatic athletes with patellar tendon abnormalities (PTA) (n = 13), asymptomatic athletes with PTA (n = 14), and a control group of asymptomatic athletes without PTA (n = 14). Participants underwent a laboratory biomechanical jump-landing assessment and wore an accelerometer for 1 week of physical activity monitoring. RESULTS: The symptomatic group demonstrated significantly less patellar tendon force loading impulse in the involved limb compared with both the control and asymptomatic groups (P<.05), with large effects (d = 0.91-1.40). There were no differences in physical activity between the 3 groups (P>.05). CONCLUSION: Young male athletes with symptomatic patellar tendinopathy demonstrated smaller magnitudes of patellar tendon force loading impulse during landing compared to both asymptomatic athletes with patellar tendinopathy and healthy control participants. However, these 3 distinct groups did not differ in general measures of physical activity. Future investigations should examine whether comprehensively monitoring various loading metrics may be valuable to avoid both underloading and overloading patterns in athletes with patellar tendinopathy. J Orthop Sports Phys Ther 2020;50(3):158-166. Epub 6 Jan 2020. doi:10.2519/jospt.2020.9065.

Hop Testing Lacks Strong Association With Key Outcome Variables After Primary Anterior Cruciate Ligament Reconstruction: A Systematic Review.

BACKGROUND: Single-legged hop tests are commonly used assessments in return to sport (RTS) testing after anterior cruciate ligament reconstruction (ACLR). Although these tests are commonly used, their predictive validity has not yet been established. PURPOSE: To determine the strength of association between hop testing and RTS, knee reinjury, subjective report of knee function, and posttraumatic knee osteoarthritis (PTOA) after primary ACLR. Secondarily, to determine whether hop testing is able to predict a favorable result on the same outcome variables. STUDY DESIGN: Systematic review. METHODS: A systematic, computer-assisted literature search was performed in PubMed/MEDLINE, CINAHL, EMBASE, SPORTDiscus, Cochrane Library, and ClinicalTrials.gov. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed when conducting and reporting this review. Primary outcome variables for this review were self-report of knee function, return to preinjury level of activity, presence of reinjury, and presence of PTOA. The Oxford Centre for Evidence-Based Medicine Levels of Evidence tool was used to assess the level of evidence for each included study. Quality assessment of each included study was performed through use of a modified Downs and Black scale. Available metrics were tabulated based on outcome variables. RESULTS: Overall, 21 studies (4476 patients) met inclusion for this review. The majority of evidence (95.2%) was of moderate to high methodologic quality. The most commonly associated outcome measure was the International Knee Documentation Committee (IKDC) score, with Pearson correlation coefficients ranging from 0.20 to 0.60. The strength of association between the Knee injury and Osteoarthritis Outcome Score (KOOS) and hop testing ranged from -0.10 to 0.62 in 4 studies. In all, 10 studies examined the relationship between hop testing and RTS, with variable association statistics reported. No meaningful association was found between hop testing and knee reinjury in 2 studies. Worse preoperative hop testing was associated with PTOA in 1 study. CONCLUSION: Hop testing appears to possess fair association to subjective report of knee function measured by the KOOS and IKDC and a patient's ability to RTS after ACLR. Insufficient evidence is available to determine the relationship between hop testing and PTOA and knee reinjury. Predictive validity cannot be established based on available literature.

Gait Mechanics and T1ρ MRI of Tibiofemoral Cartilage 6 Months after ACL Reconstruction.

PURPOSE: Aberrant walking biomechanics after anterior cruciate ligament reconstruction (ACLR) are hypothesized to be associated with deleterious changes in knee cartilage. T1ρ magnetic resonance imaging (MRI) is sensitive to decreased proteoglycan density of cartilage. Our purpose was to determine associations between T1ρ MRI interlimb ratios (ILR) and walking biomechanics 6 months after ACLR. METHODS: Walking biomechanics (peak vertical ground reaction force (vGRF), vGRF loading rate, knee extension moment, knee abduction moment) were extracted from the first 50% of stance phase in 29 individuals with unilateral ACLR. T1ρ MRI ILR (ACLR limb/uninjured limb) was calculated for regions of interest in both medial and lateral femoral (LFC) and medial and lateral tibial condyles. Separate, stepwise linear regressions were used to determine associations between biomechanical outcomes and T1ρ MRI ILR after accounting for walking speed and meniscal/chondral injury (P ≤ 0.05). RESULTS: Lesser peak vGRF in the ACLR limb was associated with greater T1ρ MRI ILR for the LFC (posterior ΔR = 0.14, P = 0.05; central ΔR = 0.15, P = 0.05) and medial femoral condyle (central ΔR = 0.24, P = 0.01). Lesser peak vGRF loading rate in the ACLR limb (ΔR = 0.21, P = 0.02) and the uninjured limb (ΔR = 0.27, P = 0.01) was associated with greater T1ρ MRI ILR for the anterior LFC. Lesser knee abduction moment for the injured limb was associated with greater T1ρ MRI ILR for the anterior LFC (ΔR = 0.16, P = 0.04) as well as the posterior medial tibial condyle (ΔR = 0.13, P = 0.04). CONCLUSION: Associations between outcomes related to lesser mechanical loading during walking and greater T1ρ MRI ILR were found 6 months after ACLR. Although preliminary, our results suggest that underloading of the ACLR limb at 6 months after ACLR may be associated with lesser proteoglycan density in the ACLR limb compared with the uninjured limb.

Association between double-leg squat and single-leg squat performance and injury incidence among incoming NCAA Division I athletes: A prospective cohort study.

OBJECTIVES: Determine the association between performance on the double-leg squat (DLS) and single-leg squat (SLS) and prospective injury incidence in athletes. DESIGN: Prospective cohort study. SETTING: National Collegiate Athletic Association (NCAA) Division I university. PARTICIPANTS: 111 incoming NCAA Division I athletes from 10 varsity sports teams. MAIN OUTCOME MEASURES: Performance on the DLS and SLS were assessed as "poor" or "non-poor." Lower extremity (LE) injury data for the following year were extracted from electronic medical records. Multivariate Poisson regression was used to compare the incidence of LE injuries in athletes with poor versus non-poor performance on the DLS and SLS. RESULTS: The final models for the DLS and SLS were adjusted for sex and LE injury history and yielded an incidence rate ratio (IRR) of 1.33 (95% CI: 0.80 2.22) for the DLS and 1.62 (95% CI: 0.98, 2.66) for the SLS when comparing poor to non-poor movers. CONCLUSIONS: Athletes with poor LE movement quality assessed on the DLS or SLS had greater incidence of LE injury than those with non-poor movement quality. This is the first study to demonstrate an association between performance on the double-leg squat and single-leg squat and injury risk in NCAA athletes.

Walking gait asymmetries 6 months following anterior cruciate ligament reconstruction predict 12-month patient-reported outcomes.

The study sought to determine the association between gait biomechanics (vertical ground reaction force [vGRF], vGRF loading rate [vGRF-LR]) collected 6 months following anterior cruciate ligament reconstruction (ACLR) with patient-reported outcomes at 12 months following ACLR. Walking gait biomechanics and all subsections of the Knee Injury and Osteoarthritis Outcomes Score (KOOS) were collected at 6 and 12 months following ACLR, respectively, in 25 individuals with a unilateral ACLR. Peak vGRF and peak instantaneous vGRF-LR were extracted from the first 50% of the stance phase. Limb symmetry indices (LSI) were used to normalize outcomes in the ACLR limb to that of the uninjured limb (ACLR/uninjured). Linear regression analyses were used to determine associations between biomechanical outcomes and KOOS while accounting for walking speed. Receiver operator characteristic curves were used to determine the accuracy of 6-month biomechanical outcomes for identifying individuals with acceptable patient-reported outcomes, using previously defined KOOS cut-off scores, 12 months post-ACLR. Individuals with lower peak vGRF LSI 6 months post-ACLR demonstrated worse patient-reported outcomes (KOOS Pain, Activities of Daily life, Sport and Recreation, Quality of Life) at the 12-month exam. A peak vGRF LSI ≥0.99 6 months following ACLR associated with 13.33× higher odds of reporting acceptable patient-reported outcomes 12 months post-ACLR. Lesser peak vGRF LSI during walking at 6-months post-ACLR may be a critical indicator of worse future patient-reported outcomes. Clinical significance achieving early symmetrical lower extremity loading and minimizing under-loading of the ACLR limb during walking may be a potential therapeutic target for improving patient-reported outcomes post-ACLR. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2932-2940, 2018.