Lower extremity and trunk sagittal plane coordination strategies and kinetic distribution during landing in males and females.

Force attenuation during landing requires coordinated motion of the ankle, knee, hip, and trunk, and strategies may differ between sexes. Sagittal plane coordination of the ankle/knee, knee/hip, and knee/trunk, and lower extremity and trunk kinematics and kinetics was compared throughout landing between 28 males and 28 females. Coordination was assessed with a modified vector coding technique and binning analysis. Total support moments (TSM), each joint's percent contribution, and timing of the TSM were compared. Females landed with less isolated knee flexion in the ankle/knee, knee/hip, and knee/trunk couplings, but more simultaneous ankle/knee flexion, less simultaneous knee flexion/hip extension, and more simultaneous trunk/knee flexion. Females landed with larger plantarflexion angles from 0-16% and smaller trunk flexion angles from 0-78%. In females, absolute TSM were larger from 0-6% and smaller from 42-100%, and normalized TSM were larger from 0-8% and 26-42%. Females had greater ankle contribution to the TSM from 14-15% and 29-35%, smaller absolute peak TSM, and the peak TSM occurred earlier. Females compensated for less isolated knee flexion with greater simultaneous ankle/knee flexion early in landing and knee/trunk flexion later in landing. Coordination and TSM differences may influence force attenuation strategies and have implications for knee injury disparity between sexes.

Cartilage deformation following a walking bout in individuals with anterior cruciate ligament reconstruction.

The purpose was to (1) compare the effect of a walking bout on femoral cartilage deformation between limbs with and without anterior cruciate ligament reconstruction (ACLR) and (2) examine the association between gait kinetics and the magnitude of cartilage deformation. A total of 30 individuals with primary unilateral ACLR completed this study [14 male, 16 female; age = 22.57 (3.78) years; body mass index (BMI) = 25.88 (5.68) kg/m2 ; time since ACLR = 61.00 (16.43) months]. Overground walking biomechanics were assessed on day 1, and a 30-min walking bout or 30-min resting bout (control) were completed on days 2 and 3 (counterbalanced order). Femoral cartilage thickness was measured using ultrasound before, immediately following, and 30-min following each intervention. Linear mixed effects models compared the effect of walking on cartilage thickness between the ACLR and contralateral limbs after adjusting for sex, BMI, speed, and the number of steps. Stepwise regression examined the association between the external knee flexion and adduction moments and cartilage deformation following walking. There was a significant limb × time interaction for medial cartilage thickness. Post hoc analyses indicated that cartilage thickness decreased immediately following walking in the contralateral but not ACLR limb. Main effects of limb were observed for medial, central, and lateral cartilage thickness indicating thicker cartilage in the ACLR compared with contralateral limb. A higher knee adduction moment was associated with greater cartilage deformation in the ACLR limb. Femoral cartilage in the ACLR limb exhibited a less dynamic response to walking than the uninvolved limb, which may be due to habitual underloading during gait.

Lower extremity coordination strategies to mitigate dynamic knee valgus during landing in males and females.

Frontal and sagittal plane landing biomechanics differ between sexes but reported values don't account for simultaneous segment or joint motion necessary for a coordinated landing. Frontal and sagittal plane coordination patterns, angles, and moments were compared between 28 males and 28 females throughout the landing phase of a drop vertical jump. Females landed with less isolated thigh abduction (p = 0.018), more in-phase motion (p < 0.001), and more isolated shank adduction (p = 0.028) between the thigh and shank in the frontal plane compared with males. Females landed with less in-phase (p = 0.012) and more anti-phase motion (p = 0.019) between the thigh and shank in the sagittal plane compared with males. Females landed with less isolated knee flexion (p = 0.001) and more anti-phase motion (p < 0.001) between the sagittal and frontal plane knee coupling compared with males. Waveform and discrete metric analyses revealed females land with less thigh abduction from 20 % to 100 % and more shank abduction from 0 to 100 % of landing, smaller knee adduction at initial contact (p = 0.002), greater peak knee abduction angles (p = 0.015), smaller knee flexion angles at initial contact (p = 0.035) and peak (p = 0.034), greater peak knee abduction moments (p = 0.024), greater knee abduction angles from 0 to 13 % and 19 to 30 %, greater knee abduction moments from 19 to 25 %, and smaller knee flexion moments from 3 to 5 % of landing compared with males. Females utilize greater frontal plane motion compared with males, which may be due to different inter-segmental joint coordination and smaller sagittal plane angles. Larger knee abduction angles and greater knee adduction motion in females are due to aberrant shank abduction rather than thigh adduction.

Changes in Performance on Common Return-to-Sport Tests During a Collegiate Women's Soccer Season: Implications for Baseline Testing.

BACKGROUND: Baseline testing of objective lower limb function may help clinicians make more informed return-to-sport (RTS) decisions in the event of an anterior cruciate ligament (ACL) injury. However, as these tests are based on physical performance, it is possible that they improve during the season as athletes get stronger and fitter. Hence, it may be difficult to ascertain the patient's preinjury status and have an accurate reference for comparison when determining readiness for RTS. The purpose of this study was to examine changes in common ACL RTS tests during a college soccer season to determine the most appropriate time to perform baseline testing. HYPOTHESIS: Hop test performance will improve across the season. STUDY DESIGN: Descriptive laboratory; prospective cohort. LEVEL OF EVIDENCE: Level 4. METHODS: A total of 31 women's soccer players from 1 NCAA Division I university agreed to participate this study. Participants performed 4 single-leg hop tests and the 505-agility test to measure cutting speed on 3 occasions: preseason (PRE), midseason (MID), and end-of-season (END). Performance on each test was compared across days to determine whether performance increased during the season. As a secondary analysis, limb symmetry index (LSI) was also compared across the season. RESULTS: A total of 23 participants (age, 19.7 ± 1.3 years; height, 1.69 ± 0.07 m; weight 60.9 ± 7.2 kg) completed all 3 testing sessions during the season. Performance during PRE was better than MID and END for all hop tests (all P < 0.01). LSI did not change during the season (P value range, 0.18-0.79). CONCLUSION: Performance on the hop tests was best during preseason and declined thereafter, which may be reflective of cumulative fatigue. CLINICAL RELEVANCE: Baseline testing of RTS tests performed during preseason may provide an accurate representation of an athlete's best abilities over the course of a collegiate soccer season. Preseason testing would also enable athletic trainers to acquire baseline data for all athletes before they are injured.

Sex-Specific associations between hip muscle strength and foot progression angle.

The foot progression angle (FPA) influences knee loading during gait, but its determinants are unclear. The purpose of this study was to compare FPA between males and females and also examine the association between lower extremity kinematics during gait, hip strength, and the FPA. 25 males and 25 females completed 5 gait trials while FPA and frontal and transverse plane hip and knee angles were calculated from the dominant limb during the foot flat portion of stance. Hip extensor/flexor, abductor/adductor, and internal/external rotator strength were evaluated using maximum voluntary isometric contractions. One-way MANOVAs compared gait and strength outcomes. Stepwise regression assessed the association between FPA, and MVIC and kinematics after accounting for speed in males and females. There was no difference in FPA between sexes (p > 0.05), but females had greater frontal and transverse plane hip angles compared with males (all p < 0.05). Greater hip abduction (p = 0.02) strength was associated with greater FPA, but only in males. In males, greater hip abductor strength may contribute to a more neutral position of the foot during gait, which could help maintain an equal knee loading distribution. Our results suggest that there are sex specific control strategies to achieve a similar FPA during gait.

Association Between the Functional Movement Screen and Landing Kinematics in Individuals With and Without Anterior Cruciate Ligament Reconstruction.

OBJECTIVES: The purpose of this study was to compare functional movement screen (FMS) scores and drop vertical jump (DVJ) kinematics between those with and without anterior cruciate ligament reconstruction (ACLR), and to evaluate the association between FMS composite score and DVJ kinematics. DESIGN: Cross-sectional. PARTICIPANTS: Sixty individuals with and without a history of ACLR. MAIN OUTCOME MEASURES: Composite FMS score and the dorsiflexion, knee-flexion, hip-flexion, knee abduction, hip adduction, and trunk-flexion angles during a DVJ. RESULTS: The FMS scores did not differ between groups (P > .05). There were smaller peak and initial contact hip-flexion angles in the ACLR and contralateral limbs compared with controls, and smaller peak dorsiflexion angles in the ACLR compared with contralateral limbs (P < .05). Lower FMS score was associated with a smaller peak dorsiflexion angle, smaller peak knee-flexion angle, and larger peak knee abduction angle in the ACLR limb (ΔR2 = .14-.23); a smaller peak dorsiflexion angle and smaller peak knee-flexion angle in the contralateral limb (ΔR2 = .17-.19); and a smaller peak dorsiflexion angle, smaller peak knee-flexion angle, and larger peak knee abduction angle in the control limb (ΔR2 = .16-.22). CONCLUSION: The FMS scores did not differ between groups, but were associated with DVJ kinematics and should be a complementary rather than substitute assessment.

Running kinetics and femoral trochlea cartilage characteristics in recreational and collegiate distance runners.

Recreational running can benefit knee cartilage, but the relationship between competitive running and knee cartilage is unclear. We compared femoral cartilage between collegiate runners, recreational runners, and controls; and evaluated the association between running amount, running kinetics and femoral cartilage characteristics. Thirty collegiate runners, 30 recreational runners, and 30 controls completed ultrasound imaging of the femoral cartilage and running gait analysis. Outcomes included cartilage thickness, and echo-intensity from the medial and lateral femoral condyles; and the peak external knee flexion (KFM) and knee adduction moments. Cartilage outcomes were compared via one-way MANOVA. The associations between running kinetics, running amount, and femoral cartilage characteristics were assessed via linear regression models adjusted for sex. No differences were found in cartilage outcomes between groups (p = 0.067). Among recreational runners, a larger peak KFM was associated with lower medial femoral cartilage echo-intensity (ΔR2 = 0.176, Δp = 0.014). In collegiate runners, a greater self-reported running amount was associated with higher medial femoral cartilage (ΔR2 = 0.117, Δp = 0.046) and lateral cartilage (ΔR2 = 0.121, Δp = 0.042) echo-intensity. Cartilage did not differ between groups, but the association between running kinetics, running amount, and knee cartilage may vary between collegiate and recreational runners.

Association Between Knee- and Hip-Extensor Strength and Running-Related Injury Biomechanics in Collegiate Distance Runners.

CONTEXT: Running-related injuries are common in distance runners. Strength training is used for performance enhancement and injury prevention. However, the association between maximal strength and distance-running biomechanics is unclear. OBJECTIVE: To determine the relationship between maximal knee- and hip-extensor strength and running biomechanics previously associated with injury risk. DESIGN: Cross-sectional study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 36 collegiate distance runners (26 men, 10 women; age = 20.0 ± 1.5 years, height = 1.74 ± 0.09 m, mass = 61.97 ± 8.26 kg). MAIN OUTCOME MEASURE(S): Strength was assessed using the 1-repetition maximum (1RM) back squat and maximal voluntary isometric contractions of the knee extensors and hip extensors. Three-dimensional running biomechanics were assessed overground at a self-selected speed. Running variables were the peak instantaneous vertical loading rate; peak forward trunk-lean angle; knee-flexion, internal-rotation, and -abduction angles and internal moments; and hip-extension, internal-rotation, and -adduction angles and internal moments. Separate stepwise linear regression models were used to examine the associations between strength and biomechanical outcomes (ΔR2) after accounting for sex, running speed, and foot-strike index. RESULTS: Greater 1RM back-squat strength was associated with a larger peak knee-flexion angle (ΔR2 = 0.110, ΔP = .045) and smaller peak knee internal-rotation angle (ΔR2 = 0.127, ΔP = .03) and internal-rotation moment (ΔR2 = 0.129, ΔP = .03) after accounting for sex, speed, and foot-strike index. No associations were found between 1RM back-squat strength and vertical loading rate, trunk lean, or hip kinematics and kinetics. Hip- and knee-extensor maximal voluntary isometric contractions were also not associated with any biomechanical variables. CONCLUSIONS: Greater 1RM back-squat strength was weakly associated with a larger peak knee-flexion angle and smaller knee internal-rotation angle and moment in collegiate distance runners. Runners who are weaker in the back-squat exercise may exhibit running biomechanics associated with the development of knee-related injuries.

Quadriceps Muscle Size, Quality, and Strength and Self-Reported Function in Individuals With Anterior Cruciate Ligament Reconstruction.

CONTEXT: Ultrasound imaging provides a cost-effective method of measuring quadriceps morphology, which may be related to self-reported function after anterior cruciate ligament reconstruction (ACLR). OBJECTIVE: To compare quadriceps morphology and strength between limbs in individuals with ACLR and matched control limbs and determine their associations with self-reported function. DESIGN: Cross-sectional study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Forty-two individuals with ACLR (females = 66%; age = 21.8 ± 2.6 years; time since ACLR = 50.5 ± 29.4 months) and 37 controls (females = 73%; age = 21.7 ± 1.2 years). MAIN OUTCOME MEASURE(S): Quadriceps peak torque (PT) and rate of torque development were assessed bilaterally. Ultrasonography was used to measure the cross-sectional area (CSA) and echo intensity (EI) of the rectus femoris, vastus lateralis (VL), and vastus medialis. Self-reported function was assessed via the International Knee Documentation Committee (IKDC) score and Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales. Paired-samples t tests were calculated to compare involved and uninvolved limbs. Independent t tests were conducted to compare groups (α = .05). Linear regression was performed to analyze associations between quadriceps function and self-reported function after accounting for time since ACLR, activity level, and sex, and models for EI added subcutaneous fat as a covariate. RESULTS: Isometric PT did not differ between limbs or groups. Involved limbs had a lower rate of torque development compared with the control (P = .01) but not the uninvolved limbs (P = .08). Vastus lateralis CSA was smaller in the involved than in the uninvolved (P < .01) but not the control limbs (P = .10). Larger VL CSA (ΔR2 = 0.103) and lower VL EI (ΔR2 = 0.076) were associated with a higher IKDC score (P < .05). Larger VL CSA was associated with greater KOOS Symptoms (ΔR2 = 0.09, P = .043) and Sport and Recreation (ΔR2 = 0.125, P = .014) scores. Lower VL EI was associated with higher KOOS Symptoms (ΔR2 = 0.104, P = .03) and Quality of Life (ΔR2 = 0.113, P = .01) scores. Quadriceps PT and rate of torque development were not associated with IKDC or KOOS subscale scores. CONCLUSIONS: Quadriceps morphology was associated with self-reported function in individuals with ACLR and may provide unique assessments of quadriceps function.

Comparison of lower limb muscle architecture and geometry in distance runners with rearfoot and forefoot strike pattern.

We examined the association between footfall pattern and characteristics of lower limb muscle function and compared lower limb muscle function between forefoot and rearfoot runners. Fifteen rearfoot and 16 forefoot runners were evaluated using ultrasonography of the gastrocnemii and tibialis anterior while strike index and heel strike angle quantified footfall pattern. Higher strike index was associated with lower medial gastrocnemius echo intensity (p = 0.05), lower lateral gastrocnemius echo intensity (p = 0.04), smaller tibialis anterior pennation angle (p = 0.05), and longer lateral gastrocnemius fascicle length (p = 0.04). Larger heel strike angle was associated with smaller medial gastrocnemius cross-sectional area (p = 0.04), shorter lateral gastrocnemius fascicle length (p < 0.01), and lower plantar flexion moment (p < 0.01). Larger plantar flexion moment was associated with lesser medial gastrocnemius echo intensity (p = 0.04), lesser lateral gastrocnemius echo intensity (p = 0.03), and greater lateral gastrocnemius fascicle length (p = 0.02). A smaller plantar flexion moment, larger heel strike angle, lower tibialis anterior echo intensity, larger tibialis anterior pennation angle, and smaller lateral gastrocnemius pennation angle were observed in rearfoot compared to forefoot runners (p < 0.05). Lower limb muscle architecture is associated with footfall pattern and ankle mechanics during running. Abbreviation: EMG: electromyographic; MG: medial gastrocnemius; LG: lateral gastrocnemius; TA: tibialis anterior; EI: echo intensity; CSA: cross-sectional area; PA: pennation angle; FL: fascicle length; FT: fat thickness.

Association between gait mechanics and ultrasonographic measures of femoral cartilage thickness in individuals with ACL reconstruction.

BACKGROUND: Individuals with anterior cruciate ligament reconstruction (ACLR) are at greater risk for knee osteoarthritis, which may be in part due to altered gait biomechanics. Articular cartilage thickness is typically imaged using magnetic resonance imaging, which is costly and lacks portability. Ultrasonography may provide an alternative imaging method for articular cartilage. It is unclear if ultrasonographic measurements of cartilage thickness are associated with gait biomechanics in individuals with ACLR. RESEARCH QUESTION: To evaluate the association between sagittal and frontal plane knee mechanics during gait and resting femoral cartilage thickness from ultrasonography. METHODS: Twenty-five females with ACLR (age = 21.7 ± 2.6 years, time since ACLR = 60.6 ± 24.8 months) completed assessments of walking biomechanics and resting femoral cartilage thickness. Linear regression examined the association between gait biomechanics and cartilage thickness at the medial (MC) and lateral (LC) femoral condyles, and intercondylar notch (IC) after accounting for time since ACLR, meniscal injury, and gait speed. RESULTS: In the ACLR limb, larger vertical ground reaction force (ΔR2 = 0.21, pΔ = 0.03), knee flexion angle (ΔR2 = 0.15, pΔ = 0.05), knee flexion excursion (KFE) (ΔR2 = 0.16, pΔ = 0.04), and knee flexion impulse (KFI) (ΔR2 = 0.23, pΔ = 0.02) were associated with thicker MC cartilage. A larger knee adduction angle (ΔR2 = 0.20, pΔ = 0.03) and knee adduction moment (KAM) (ΔR2 = 0.20, pΔ = 0.03) were associated with thinner MC thickness. Larger KFE (ΔR2 = 0.20, pΔ = 0.03) was associated with thicker LC cartilage. Gait biomechanics were not associated with IC cartilage thickness. After accounting for co-variates, the combination of KFI and KAM was predictive of MC thickness (ΔR2 = 0.37, pΔ = 0.01; Total R2 = 0.52, p = 0.02). Meniscal injury, KAM, and KFI were significant predictors in the model. In the contralateral limb, KFE was associated with thicker MC cartilage (ΔR2 = 0.16, pΔ = 0.05). SIGNIFICANCE: Sagittal and frontal plane knee mechanics during gait are uniquely associated with ultrasonographic measurements of femoral cartilage thickness in individuals with ACLR. Furthermore, concomitant medial meniscal injury was associated with thinner MC cartilage.

Bilateral Alterations in Running Mechanics and Quadriceps Function Following Unilateral Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Following anterior cruciate ligament reconstruction (ACLR), individuals have quadriceps muscle impairments that influence gait mechanics and may contribute to an elevated risk of knee osteoarthritis. OBJECTIVES: To compare running mechanics and quadriceps function between individuals who have undergone ACLR and those in a control group, and to evaluate the association between quadriceps function and running mechanics. METHODS: In this controlled, cross-sectional laboratory study, 38 individuals who previously underwent primary unilateral ACLR (mean ± SD time since reconstruction, 48.0 ± 25.0 months) were matched to 38 control participants based on age, sex, and body mass index, and underwent assessments of quadriceps muscle performance and running biomechanics. Quadriceps muscle performance was assessed via isokinetic and isometric knee extension peak torque and rate of torque development (RTD) over 2 time frames: 0 to 100 milliseconds (RTD100) and 0 to 200 milliseconds (RTD200). Running evaluation included assessment of the knee flexion angle (KFA), knee extension moment (KEM), rate of knee extension moment (RKEM), vertical instantaneous loading rate, and vertical impact peak. RESULTS: On average, there was a smaller KFA (P = .016) in the involved limb compared to the uninvolved limb in the ACLR group. Compared to limbs in the control group, involved limbs in the ACLR group had lower RTD100 (P = .015), lower peak torque at 60°/s (P = .007), lower peak torque at 180°/s (P = .016), smaller KFA (P<.001), lower KEM (P = .001), lower RKEM (P = .004), and higher vertical instantaneous loading rate (P = .016). Compared to limbs in the control group, uninvolved limbs in the ACLR group had lower RTD100 (P = .003), lower peak torque at 60°/s (P = .017), and smaller KFA (P = .01). For the involved limbs in the ACLR group, there was a low correlation between isokinetic peak torque at 180°/s and RKEM (r = 0.38, P = .01), and a negligible correlation between RTD100 and RKEM (r = 0.26, P<.05). No differences were found in isometric strength for any comparison. CONCLUSION: Individuals who have undergone ACLR have bilateral alterations in running mechanics that are weakly associated with diminished quadriceps muscle performance. J Orthop Sports Phys Ther 2018;48(12):960-967. Epub 22 Jul 2018. doi:10.2519/jospt.2018.8170.

Factors Affecting the Completion of Genitourinary Physical Examinations Prior to Urologic Consultation.

BACKGROUND: Proper instruction during medical training regarding performing adequate physical examinations prior to urologic consultations greatly improves patient care. We evaluated the frequency of genitourinary (GU) physical examinations performed prior to urologic consultation to determine the influence of factors affecting the completion of these examinations. METHODS: Between January 2013 and December 2014, 1,596 consultations were requested by primary providers and completed by the urology department at a major tertiary care teaching institution. We reviewed patient medical records retrospectively and recorded the number of GU examinations performed prior to consultation. Patient demographics were evaluated for trends in the rates of examination. A total of 9 available urology residents saw at least one consult each. RESULTS: We identified a total of 1,596 urologic consultations during the study period, of which 233 of 407 (57.2%) (51 female and 182 male patients) received GU examinations prior to the urologic consult in the emergency department (ED) and 394 of 1,189 (33.1%) (118 female and 276 male patients) received GU examinations by the inpatient care team. Staff in the ED were 3.11 times more likely to perform a GU examination on a male patient than a female patient, and the inpatient teams were 1.48 times more likely to perform a GU examination on a male patient than a female patient. The likelihood of examination by either team was low in patients aged ≥65 years. CONCLUSION: Prior to urologic consultation, GU examinations are inconsistently performed. This variability may affect patient care and could be the subject of a future study.

Effect of Whole-Body Vibration on Sagittal Plane Running Mechanics in Individuals With Anterior Cruciate Ligament Reconstruction: A Randomized Crossover Trial.

OBJECTIVE: To examine the effect of whole-body vibration (WBV) on running biomechanics in individuals with anterior cruciate ligament reconstruction (ACLR). DESIGN: Single-blind randomized crossover trial. SETTING: Research laboratory. PARTICIPANTS: Individuals (N=20) with unilateral ACLR (age [± SD]=22.3 [±3.3] years; mass=71.8 [±15.3] kg; time since ACLR=44.9 [±22.8] months; 15 females, 10 patellar tendon autograft, 7 hamstrings autograft, 3 allograft; International Knee Documentation Committee Score=83.5 [±9.3]). MAIN OUTCOME MEASURE: Participants performed isometric squats while being exposed to WBV or no vibration (control). WBV and control conditions were delivered in a randomized order during separate visits separated by 1-week washout periods. Running biomechanics of the injured and uninjured limbs were evaluated before and immediately after each intervention. Dependent variables included peak vertical ground reaction force (GRF) and loading rate (LR), peak knee flexion angle and external moment, and knee flexion excursion during the stance phase of running. RESULTS: There was an increase in knee flexion excursion (+4.1°, 95% confidence interval [CI]: 0.65, 7.5°) and a trend toward a reduction in instantaneous LR after WBV in the injured limb (-4.03 BW/sec-1, 95% CI -0.38, -7.69). No effect was observed on peak GRF, peak knee flexion angle, or peak external knee flexion moment, and no effect was observed in the uninjured limb. CONCLUSIONS: Our findings indicate that a single session of WBV acutely increases knee flexion excursion. WBV could be useful to improve running characteristics in individuals with knee pathology.

Quadriceps Function and Knee Joint Ultrasonography after ACL Reconstruction.

PURPOSE: Individuals with anterior cruciate ligament reconstruction (ACLR) are at greater risk for knee osteoarthritis, partially because of chronic quadriceps dysfunction. Articular cartilage is commonly assessed using magnetic resonance imaging and radiography, but these methods are expensive and lack portability. Ultrasound imaging may provide a cost-effective and portable alternative for imaging the femoral cartilage. The purpose of this study was to compare ultrasonography of the femoral cartilage between the injured and uninjured limbs of individuals with unilateral ACLR, and to examine the association between quadriceps function and ultrasonographic measures of femoral cartilage. METHODS: Bilateral femoral cartilage thickness and quadriceps function were assessed in 44 individuals with unilateral ACLR. Quadriceps function was assessed using peak isometric strength, and early (RTD100) and late (RTD200) rate of torque development. RESULTS: Cartilage thickness at the medial femoral condyle (P < 0.001) and femoral cartilage cross-sectional area (P = 0.007) were smaller in the injured compared with the uninjured limb. After accounting for time since ACLR, quadriceps peak isometric strength was associated with cartilage thickness at the medial femoral condyle (r = 0.35, P = 0.02) and femoral cartilage cross-sectional area (r = 0.28, P = 0.04). RTD100 and RTD200 were not associated with femoral cartilage thickness or cross-sectional area. CONCLUSIONS: Individuals with ACLR have thinner cartilage in their injured limb compared with uninjured limb, and cartilage thickness is associated with quadriceps function. These results indicate that ultrasonography may be useful for monitoring cartilage health and osteoarthritis progression after ACLR.

The Influence of Lower Extremity Lean Mass on Landing Biomechanics During Prolonged Exercise.

CONTEXT: The extent to which lower extremity lean mass (LELM) relative to total body mass influences one's ability to maintain safe landing biomechanics during prolonged exercise when injury incidence increases is unknown. OBJECTIVES: To examine the influence of LELM on (1) pre-exercise lower extremity biomechanics and (2) changes in biomechanics during an intermittent exercise protocol (IEP) and (3) determine whether these relationships differ by sex. We hypothesized that less LELM would predict higher-risk baseline biomechanics and greater changes toward higher-risk biomechanics during the IEP. DESIGN: Cohort study. SETTING: Controlled laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 59 athletes (30 men: age = 20.3 ± 2.0 years, height = 1.79 ± 0.05 m, mass = 75.2 ± 7.2 kg; 29 women: age = 20.6 ± 2.3 years, height = 1.67 ± 0.08 m, mass = 61.8 ± 9.0 kg) participated. INTERVENTION(S): Before completing an individualized 90-minute IEP designed to mimic a soccer match, participants underwent dual-energy x-ray absorptiometry testing for LELM. MAIN OUTCOME MEASURE(S): Three-dimensional lower extremity biomechanics were measured during drop-jump landings before the IEP and every 15 minutes thereafter. A previously reported principal components analysis reduced 40 biomechanical variables to 11 factors. Hierarchical linear modeling analysis then determined the extent to which sex and LELM predicted the baseline score and the change in each factor over time. RESULTS: Lower extremity lean mass did not influence baseline biomechanics or the changes over time. Sex influenced the biomechanical factor representing knee loading at baseline (P = .04) and the changes in the anterior cruciate ligament-loading factor over time (P = .03). The LELM had an additional influence only on women who possessed less LELM (P = .03 and .02, respectively). CONCLUSIONS: Lower extremity lean mass influenced knee loading during landing in women but not in men. The effect appeared to be stronger in women with less LELM. Continually decreasing knee loading over time may reflect a strategy chosen to avoid injury. A minimal threshold of LELM may be needed to safely perform landing maneuvers, especially during prolonged exercise when the injury risk increases.

Changes in fatigue, multiplanar knee laxity, and landing biomechanics during intermittent exercise.

CONTEXT: Knee laxity increases during exercise. However, no one, to our knowledge, has examined whether these increases contribute to higher-risk landing biomechanics during prolonged, fatiguing exercise. OBJECTIVES: To examine associations between changes in fatigue (measured as sprint time [SPTIME]), multiplanar knee laxity (anterior-posterior [APLAX], varus-valgus [VVLAX] knee laxity, and internal-external rotation [IERLAX]) knee laxity and landing biomechanics during prolonged, intermittent exercise. DESIGN: Descriptive laboratory study. SETTING: Laboratory and gymnasium. PATIENTS OR OTHER PARTICIPANTS: A total of 30 male (age = 20.3 ± 2.0 years, height = 1.79 ± 0.05 m, mass = 75.2 ± 7.2 kg) and 29 female (age = 20.5 ± 2.3 years, height = 1.67 ± 0.08 m, mass = 61.8 ± 9.0 kg) competitive athletes. INTERVENTION(S): A 90-minute intermittent exercise protocol (IEP) designed to simulate the physiologic and biomechanical demands of a soccer match. MAIN OUTCOME MEASURE(S): We measured SPTIME, APLAX, and landing biomechanics before and after warm-up, every 15 minutes during the IEP, and every 15 minutes for 1 hour after the IEP. We measured VVLAX and IERLAX before and after the warm-up, at 45 and 90 minutes during the IEP, and at 30 minutes after the IEP. We used hierarchical linear modeling to examine associations between exercise-related changes in SPTIME and knee laxity with exercise-related changes in landing biomechanics while controlling for initial (before warm-up) knee laxity. RESULTS: We found that SPTIME had a more global effect on landing biomechanics in women than in men, resulting in a more upright landing and a reduction in landing forces and out-of-plane motions about the knee. As APLAX increased with exercise, women increased their knee internal-rotation motion (P = .02), and men increased their hip-flexion motion and energy-absorption (P = .006) and knee-extensor loads (P = .04). As VVLAX and IERLAX increased, women went through greater knee-valgus motion and dorsiflexion and absorbed more energy at the knee (P ≤ .05), whereas men were positioned in greater hip external and knee internal rotation and knee valgus throughout the landing (P = .03). The observed fatigue- and laxity-related changes in landing biomechanics during exercise often depended on initial knee laxity. CONCLUSIONS: Both exercise-related changes in fatigue and knee laxity were associated with higher-risk landing biomechanics during prolonged exercise. These relationships were more pronounced in participants with greater initial knee laxity.

The effect of equalizing landing task demands on sex differences in lower extremity energy absorption.

BACKGROUND: Less lean mass and strength may result in greater relative task demands on females compared to males when landing from a standardized height and could explain sex differences in energy absorption strategies. We compared the magnitude of sex differences in energy absorption when task demands were equalized relative to the amount of lower extremity lean mass available to dissipate kinetic energy upon landing. METHODS: Male-female pairs (n=35) were assessed for lower extremity lean mass with dual-energy X-ray absorptiometry. Relative task demands were calculated when landing from a standardized height. Based on the difference in lower extremity lean mass within each pair, task demands were equalized by increasing the drop height for males. Joint energetics were measured while landing from the two heights. Multivariate repeated measures ANOVAs compared the magnitude of sex differences in joint energetics between conditions. FINDINGS: The multivariate test for absolute energy absorption was significant (P<0.01). The magnitude of sex difference in energy absorption was greater at the hip and knee (both P<0.01), but not the ankle (P=0.43) during the equalized condition compared to the standardized and exaggerated conditions (all P<0.01). There was no difference in the magnitude of sex differences between equalized, standardized and exaggerated conditions for relative energy absorption (P=0.18). INTERPRETATION: Equalizing task demands increased the difference in absolute hip and knee energy absorption between sexes, but had no effect on relative joint contributions to total energy absorption. Sex differences in energy absorption are likely influenced by factors other than differences in relative task demands.

Changes in drop-jump landing biomechanics during prolonged intermittent exercise.

BACKGROUND: As injury rates rise in the later stages of sporting activities, a better understanding of lower extremity biomechanics in the later phases of gamelike situations may improve training and injury prevention programs. HYPOTHESIS: Lower extremity biomechanics of a drop-jump task (extracted from a principal components analysis) would reveal factors associated with risk of anterior cruciate ligament injury during a 90-minute individualized intermittent exercise protocol (IEP) and for 1 hour following the IEP. STUDY DESIGN: Controlled laboratory study. LEVEL OF EVIDENCE: Level 4. METHODS: Fifty-nine athletes (29 women, 30 men) completed 3 sessions. The first session assessed fitness for an IEP designed to simulate the demands of a soccer match. An experimental session assessed drop-jump biomechanics, after a dynamic warm-up, every 15 minutes during the 90-minute IEP, and for 1 hour following the IEP. A control session with no exercise assessed drop-jump performance at the same intervals. RESULTS: Two biomechanical factors early in the first half (hip flexion at initial contact and hip loading; ankle loading and knee shear force) decreased at the end of the IEP and into the 60-minute recovery period, while a third factor (knee loading) decreased only during the recovery period (P ≤ 0.05). CONCLUSION: The individualized sport-specific IEP may have more subtle effects on landing biomechanics when compared with short-term, exhaustive fatigue protocols. CLINICAL RELEVANCE: Potentially injurious landing biomechanics may not occur until the later stages of soccer activity.

Multiplanar knee laxity increases during a 90-min intermittent exercise protocol.

PURPOSE: This study aimed to examine changes in sagittal (AP LAX), frontal (VV LAX), and transverse (IER LAX) plane knee laxity in men and women during an intermittent exercise protocol (IEP) simulating the intensity and duration of a soccer match. METHODS: Intercollegiate/club athletes (29 females and 30 males) were measured on AP LAX (-90 to 130 N) before and after warm-up and every 15 min during and for 1 h after the IEP. VV LAX (± 10 N · m) and IER LAX (± 5 N · m) were measured before and after warm-up, at the end of each 45-min half, and at 30 min after exercise. Values were compared to a control (no exercise) condition. RESULTS: Compared to control condition, females increased AP LAX and VV LAX during the IEP, whereas males did not (P < 0.037). AP LAX increased within 15 min of exercise (9.5 ± 2.1 mm), and peak values obtained at the end of the first (10.1 ± 2.0 mm) and second half (10.1 ± 2.1 mm) were 12% greater than before warm-up values (9.0 ± 1.8 mm). VV LAX increased before warm-up (9.5° ± 3.4°) to the end of each half (both 10.4° ± 3.2°; 10% increase) and remained elevated 30 min after exercise (10.5° ± 2.9°). Both sexes increased IER LAX from before warm-up (25.5° ± 6.1°) to all time points (after warm-up = 26.6° ± 6.0°, first half = 27.0° ± 6.6°, second half = 27.3° ± 6.5°, 30 min after exercise = 26.95° ± 5.7°; P = 0.007). Changes in AP LAX (-0.10 to 5.9 mm), VV LAX (-1.7° to 5.7°), and IER LAX (-4.1° to 13.3°) during exercise varied considerably among individuals in both sexes, with a larger proportion of females experiencing substantial changes in AP LAX and VV LAX. CONCLUSIONS: Although exercise-related knee laxity changes were more pronounced in females, there was a subset of both males and females who experienced substantial knee laxity increases during exercise. Whether these individuals are more susceptible to higher-risk lower extremity biomechanics and injury risk later in a game or practice is currently under investigation.