Altered Knee and Ankle Kinematics During Squatting in Those With Limited Weight-Bearing–Lunge Ankle-Dorsiflexion Range of Motion

Context:

Ankle-dorsiflexion (DF) range of motion (ROM) may influence movement variables that are known to affect anterior cruciate ligament loading, such as knee valgus and knee flexion. To our knowledge, researchers have not studied individuals with limited or normal ankle DF-ROM to investigate the relationship between those factors and the lower extremity movement patterns associated with anterior cruciate ligament injury.

Objective:

To determine, using 2 different measurement techniques, whether knee- and ankle-joint kinematics differ between participants with limited and normal ankle DF-ROM.

Design:

Cross-sectional study.

Setting:

Sports medicine research laboratory.

Patients or Other Participants:

Forty physically active adults (20 with limited ankle DF-ROM, 20 with normal ankle DF-ROM).

Main Outcome Measure(s):

Ankle DF-ROM was assessed using 2 techniques: (1) nonweight-bearing ankle DF-ROM with the knee straight, and (2) weight-bearing lunge (WBL). Knee flexion, knee valgus-varus, knee internal-external rotation, and ankle DF displacements were assessed during the overhead-squat, single-legged squat, and jump-landing tasks. Separate 1-way analyses of variance were performed to determine whether differences in knee- and ankle-joint kinematics existed between the normal and limited groups for each assessment.

Results:

We observed no differences between the normal and limited groups when classifying groups based on nonweight-bearing passive-ankle DF-ROM. However, individuals with greater ankle DF-ROM during the WBL displayed greater knee-flexion and ankle-DF displacement and peak knee flexion during the overhead-squat and single-legged squat tasks. In addition, those individuals also demonstrated greater knee-varus displacement during the single-legged squat.

Conclusions:

Greater ankle DF-ROM assessed during the WBL was associated with greater knee-flexion and ankle-DF displacement during both squatting tasks as well as greater knee-varus displacement during the single-legged squat. Assessment of ankle DF-ROM using the WBL provided important insight into compensatory movement patterns during squatting, whereas nonweight-bearing passive ankle DF-ROM did not. Improving ankle DF-ROM during the WBL may be an important intervention for altering high-risk movement patterns commonly associated with noncontact anterior cruciate ligament injury.Key Words: knee flexion, knee valgus, knee varus, anterior cruciate ligament, squat, jump landing

Key Points

• Nonweight-bearing ankle-dorsiflexion range of motion was not associated with changes in ankle or knee kinematics during the overhead-squat, single-legged squat, or jump-landing task.
• Greater ankle-dorsiflexion range of motion during the weight-bearing lunge resulted in greater sagittal-plane motion at the knee and ankle during the squatting tasks but not the jump landing.
• Compared with nonweight-bearing passive measures, ankle-dorsiflexion range of motion during the weight-bearing lunge may be a more sensitive measure for identifying those with high-risk movement patterns.

An estimated 350 000 anterior cruciate ligament (ACL) reconstructions are performed annually in the United States,¹ with most of those injuries occurring during sport participation by individuals between 15 and 25 years old.^2,3 Recent estimates have illustrated a national increase in ACL injuries of 67.8% during a 10-year period.⁴ In addition to those concerning numbers, 70% of ACL injuries result from noncontact mechanisms, defined as no contact with another player or piece of equipment, such as plant-and-cut maneuvers, landing from a jump, and decelerating.^5,6 The high incidence of noncontact ACL injury is driving researchers to investigate possible biomechanical and neuromuscular factors that may contribute to ACL injury.Dynamic maneuvers, such as the overhead-squat (OHS),⁷ single-legged squat (SLS),⁸ and jump-landing (JL)⁹ tasks, have been used in laboratory and clinical settings to elucidate faulty lower extremity movement patterns and to identify individuals potentially at risk for ACL injury. Some of the key patterns of movement identified are side-to-side (frontal-plane) or rotational (transverse-plane) movements at the knee because those movements place the greatest load on the ACL in combination with an anterior tibial shear force (sagittal plane).¹⁰ Anterior cruciate ligament loading is exacerbated when the knee is in a minimally flexed or hyperextended position in conjunction with a large quadriceps muscle contraction.^11,12 Noncontact ACL injury mechanisms are often described as landing in a relatively extended knee position (sagittal plane) combined with frontal- and transverse-plane loading.¹² Movement at adjacent joints also influences knee loading. Researchers^7,13,14 have identified a potential relationship between limited dorsiflexion range of motion (DF-ROM) in the ankle and knee kinematics, such as medial knee displacement, which may increase the risk of ACL injury. Ideally, those squatting and JL movements would include primarily sagittal-plane motion at all lower extremity joints to perform properly and absorb and dissipate the landing forces.¹⁵ Restrictions in the ability to move through ankle DF during weight bearing can interfere with performance by potentially increasing the plantar-flexion moment when the ankle is dorsiflexed¹⁶ and restricting the forward rotation of the shank at the ankle when the foot is in contact with the ground.¹⁷ Limitations in ankle-DF displacement are often accompanied by less sagittal-plane motion at proximal joints, such as the knee and trunk.^15,18 Therefore, ankle-DF restrictions may contribute to limited sagittal-plane motion at the knee and thereby contribute to compensatory increases in frontal- and transverse-plane motions that are potentially injurious to the ACL.Less DF-ROM assessed passively in a nonweight-bearing (NWB) position has been associated with greater medial-knee displacement during a variety of tasks.^7,14 Bell et al⁷ studied individuals with medial-knee displacement, which is a clinical observation of dynamic valgus collapse, and observed that participants who displayed medial-knee displacement during an OHS had approximately 20% less NWB, passive ankle DF than did those participants without medial-knee displacement. Furthermore, the medial-knee displacement observed during the OHS was corrected when a 2-in (5.08-cm) lift was placed under the heel; the correction may have occurred because of the increased tibial angle in the anterior direction. Less passive DF-ROM assessed in NWB movements has also been associated with greater frontal-plane knee excursion during a double-legged drop-landing in young female soccer players¹⁴ and with decreased knee-flexion displacement during a jump-landing task.¹⁹Other authors have investigated ankle-DF motion during dynamic movements in relation to knee kinematics, with contrasting findings. Compared with men, women with greater DF-ROM measured during SLS²⁰ and double-legged drop landings²¹ demonstrated greater maximum knee-valgus angles. This body of research suggests that ankle DF-ROM may contribute to the amount of knee valgus (frontal plane) and knee flexion (sagittal plane) an individual uses during dynamic movement, but the relationship is unclear and requires further investigation.Previous examinations^7,14,19 of the relationship between ankle DF-ROM and knee kinematics may be limited because of the NWB, passive assessments that were often used. Weight-bearing measures of ankle DF-ROM may provide a better representation of the available ROM during functional, weight-bearing tasks.²² However, previous authors have not, to our knowledge, investigated the relationship between knee kinematics during dynamic movement and separate weight-bearing and NWB ankle DF-ROM assessments. In addition, no previous researchers, to our knowledge, have intentionally recruited a participant population with known limitations in ankle DF-ROM. Therefore, the purpose of our study was to investigate knee and ankle kinematics during dynamic tasks in participants who were identified as having limited ankle DF-ROM and to compare the results with those of participants who had normal ankle DF-ROM. Ankle-DF motion was assessed passively through both weight-bearing and NWB techniques before testing, and total displacement during dynamic movement was calculated. The goal of comparing the ROM of normal and limited groups was to find an assessment that could be used clinically to indicate how an individual will perform during a more functional task. We hypothesized that individuals with less DF-ROM, both NWB and weight bearing, would display kinematics associated with ACL loading (less sagittal-plane motion and greater frontal-plane motion) during an OHS, SLS, and JL task.     

the Influence of Walking Speed on Knee Momentand the Realizable Method of the Prosthesis

1.IntroductionThekineticandkinematicsanalysisofthelower-limbsofable-bodiesisnotonlyanimportantpartofbiomechanics,butalsothefundamentalinvestigationonrehabilitationofthepeoplewithlowerlimbdisabilities,Inlastafewyears,aprototypeofintelligentlowerlimbprosthesishasbeendevelopedatTsinghuaUniversity.Inordertolettheintelligentprosthesisbesuitabletovariablewalkingspeed,itisnecessarytostudytheinfluenceofwalkingspeedonKneemoment.Inthispaper,thedisplacementsandtemporaldistancefactorsandgroundreactionfo…     

ISBT Scientific Series – State of the Art Invited speakerProtein blood group systems: Berlin and beyond

As of July 2010, 24 of the 30 blood group systems recognized by the International Society of Blood Transfusion (ISBT) are protein-based. These proteins are oriented within the red cell membrane as single pass membrane proteins, multi-pass proteins, glycosylphosphatidylinositol-linked proteins, or adsorbed from the plasma. At the 2010 meeting of the ISBT working party on the red cell immunogenetics and blood group terminology, 14 ‘new’ high-incidence blood group antigens were ratified into 10 of the systems, one antigen was made obsolete, and a new collection was established. Early in 2012, two new protein-based blood group systems were established. Both are members of the ATP-binding cassette family of proteins.     

The Utility of Measures of Child and Adolescent Anxiety: A Meta-Analytic Review of the Revised Children's Manifest Anxiety Scale,the State–Trait Anxiety Inventory for Children,and the Child Behavior Checklist

We evaluated the ability of the Revised Children's Manifest Anxiety Scale (RCMAS), the State–Trait Anxiety Inventory for Children (STAIC), and the Child Behavior Checklist (CBCL) to (a) discriminate between youth with an anxiety disorder and youth without a disorder, (b) discriminate between youth with an anxiety disorder and youth with either externalizing disorders or affective disorders, and (c) measure treatment change. In addition, variables, including age and sex, were explored as possible moderators of instrument utility. A meta-analysis of 43 articles was conducted. A large effect size was found when the instruments were used to compare youth with an anxiety disorder to youth without a disorder. When comparing anxious youth to psychiatric control groups, the picture was mixed; the instruments were found to be useful when discriminating between youth with an anxiety disorder and youth with an externalizing disorder, but not between youth with an anxiety disorder and children and adolescents with an affective disorder. The RCMAS, STAIC, and CBCL were found to be moderately sensitive to treatment gains.     

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Pathogenesis and Immunobiology of Brucellosis: Review of Brucella–Host Interactions

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Traditionally, the genus Brucella consisted of six recognized species, grouped according to their primary host preferences, that is, B. abortus, cattle; B. melitensis, sheep and goats; B. suis, pigs; B. ovis, sheep; B. canis, dogs; and B. neotomae, wood desert rats. Recent isolates from human (B. inopinata), aquatic mammals (B. pinnipedialis and B. ceti), and a common vole (B. microti) are recognized as new species, bringing the current number to 10 species in the genus. The basis for host preference remains an open question, although there may be a role for pseudogenes that influence host adaptation. The global disease burden in livestock is enormous. Conservative estimates are that >300 million of the 1.4 billion worldwide cattle population is infected with the pathogen. Brucellosis in animals results in abortion and other disease manifestations.Brucella spp. infects humans as an incidental host. Human infection usually results from direct contact with tissues or blood from infected animals or by consumption of contaminated animal products, including unpasteurized milk and cheeses. In fact, >500,000 new human infections are estimated to occur annually. Brucellosis in humans typically presents with high, undulating fever. However, chronic brucellosis may affect many host organs, leading to arthritis, orchitis, hepatitis, encephalomyelitis, and endocarditis^2,3 (Figure 1). Arthritis represents the most common complication. The diverse manifestations of the disease complicate diagnosis. Brucellosis has eluded systematic attempts at eradication for more than a century, even in most developed countries, and no approved human vaccine is available. The low number of virulent organisms required for infection combined with the capacity for aerosolization renders Brucella spp. as category B pathogens and potential agents for bioterrorism. 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Original magnification, ×40. H&E, hematoxylin and eosin.     

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<正>Lower-extremity exoskeletons have been actively investigated in the past few decades intending to augment the locomotion performance of able-bodied users in terms of metabolic cost,load carrying capacity,fatigue,and muscle force generation.While development efforts have been extensive,lowerlimb exoskeleton devices have demonstrated limited success in achieving their augmentation goals,     

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Background  

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