Knee flexors/extensors in gait of elderly and young able-bodied men (II)

In this study the fundamental tasks of muscle activity at the knee during gait in elderly and young able-bodied subjects were identified using principal component analysis (PCA). Role discrepancies between the older and younger subjects for the actions executed by the knee flexors and extensors during the gait cycle were also investigated. The t-test for independent groups was applied to determine significant differences between spatio-temporal and peak muscle moment parameters (P<0.05). PCA as a multivariate classification and curve structure detection method was applied to the sagittal knee muscle moment curves of twenty elderly (72 +/-5.5 years) and twenty young (25 +/- 8.1 years) subjects. The first three principal components (PCs) which accounted for 80% (older) and 93% (younger) of the information were retained for further analysis. Providing stable locomotion was recognised as a major task of the knee in the older subjects, while for the younger subjects the knee contributed to both balance and propulsion. Supporting the body during single limb support should be considered the only common task at the knee level in elderly and young subjects' gait. The lack of muscle power for propulsion might be the reason for not identifying the knee extensor muscle roles in the first three major tasks during elderly gait. Functional asymmetry can be considered the result of a different ordering of the functional roles of the muscles acting at the knee level in elderly and young subjects.     

Principal component analysis of the power developed in the flexion/extension muscles of the hip in able-bodied gait

This study was undertaken to demonstrate how principal component analysis (PCA) can be used: (a) to detect the main functional structure of actions taken by hip extensors and flexors during two consecutive gait cycles of able-bodied subjects, and (b) to determine whether or not symmetrical behaviour exists between right and left hip muscle power activity. Twenty young, healthy male subjects walked along a 13 m path at a freely-chosen speed. Applying curve structure detection methods such as PCA to walking patterns can provide insight into the functional tasks accomplished by the lower limbs of able-bodied and disabled subjects. PCA was applied as a classification and curve structure detection method to hip sagittal muscle power calculated for the right and left lower limbs. Over 70% of the information provided by the first four principal components (PCs) was chosen for further biomechanical interpretation. PC1 for both right and left sides mainly described the action taken by the hip extensors/flexors corresponding to the vertical component of ground force on the respective limbs during mid-stance. Propulsion and limb preparation were identified as the second and third tasks attributed to right hip muscle power, while between limb co-ordination was recognised as the second and third functional tasks of the left hip extensors/flexors. Balance was identified as the fourth main functional contribution of the hip extensors/flexors at the right limb while for the left limb, these muscles were mainly responsible for preparing the limb to enter into new gait cycle. PCA was able to identify the four main functional contributions of hip sagittal muscle power during able-bodied gait. PCA was also able to examine the existence of functional asymmetry in gait by highlighting different task priorities at the hip level for the right and left lower limbs.     

Software for determining lower extremity muscle-tendon kinematics and moment arm lengths during flexion/extension movements.

A computer program was developed to calculate lower extremity muscle-tendon (MT) kinematics and flexion/extension moment arm (MA) lengths for any subject performing movements constrained to occur in the sagittal plane. The program requires as input subject anthropometric and time series ankle, knee, and hip angle data. Using these data a lower extremity link-segment model is constructed for each time element. Muscle-tendon attachment data and a straight line muscle model are used to calculate MT and flexion/extension moment arm lengths. A finite difference technique is used to determine MT shortening velocity. The utility of this program is demonstrated by calculating MT kinematics and MA lengths for six muscles of a single subject both as a function of joint angles and during gait.     

Longitudinal changes in knee kinematics and moments following knee arthroplasty: A systematic review

BackgroundKnee arthroplasty (KA) is recognized as an effective treatment of knee joint osteoarthritis and up to 90% of patients experience substantial pain relief. There has been no systematic review synthesizing the longitudinal changes in gait following KA. The aims of this systematic review were to determine the effects of KA on (i) frontal plane and (ii) sagittal plane kinematic and kinetic parameters during the stance phase of gait.MethodsMEDLINE (PubMed), CINAHL, SPORTdiscus (EBSCO), and Cochrane Library (Wiley) were searched until April 10th, 2014. 1,765 articles were identified, of which 19 studies describing 3-dimensional gait analysis pre- and post-KA were included. Study quality was evaluated by two reviewers independently using the Downs and Black checklist.FindingsFollowing KA, in the frontal plane, the maximum knee adduction angle and external knee adduction moment (KAM) tended to decrease. In the sagittal plane, findings suggest that the maximum knee flexion moment is increased. From the ten studies that included a healthy reference group, it was unclear whether gait variables returned to normal following KA.InterpretationOverall, it appears that KA results in a decreased peak KAM and maximum knee adduction angles, an increased peak knee flexion moment and inconsistent changes in the peak knee flexion angle. Knowledge gaps remain due to methodological inconsistencies across studies, limited statistical analysis, and largely heterogeneous sample populations. More research is needed to determine whether KA restores gait patterns to normal, or if additional rehabilitation may be needed to optimize gait following surgery for osteoarthritis.     

Stabilizing moments of force on a prosthetic knee during stance in the first steps after gait initiation

In this study, the occurrences of stabilizing and destabilizing external moments of force on a prosthetic knee during stance, in the first steps after gait initiation, in inexperienced users were investigated. Primary aim was to identify the differences in the external moments during gait initiation with the sound leg leading and the prosthetic leg leading. A prosthetic leg simulator device, with a flexible knee, was used to test able-bodied subject, with no walking aid experience. Inverse dynamics calculations were preformed to calculate the external moments. The subjects learned to control the prosthetic leg within 100 steps, without walking aids, evoking similar patterns of external moments of force during the steps after the gait initiation, either with their sound leg loading or prosthetic leg leading. Critical phases in which a sudden flexion of the knee can occur were found just after heelstrike and just before toe off, in which the external moment of force was close to the internal moment produced by a knee extension aiding spring in the opposite direction.     

Relationships between early postoperative gait biomechanical factors and patient-reported outcome measures 6 months after total knee arthroplasty

BackgroundThis study was focused on the gait parameters of the knee extensor and hip abductor muscle groups, which are believed to contribute to knee joint function improvement in early postoperative TKA. The associations between patient-reported outcome measures (PROMs) 6 months after total knee arthroplasty (TKA) and the early postoperative internal knee extension moment, knee extension negative joint power, and internal hip abduction moment while walking were investigated.MethodsTwenty-one patients who underwent primary TKA for knee osteoarthritis were included. Three weeks after TKA, gait at a comfortable speed was measured by three-dimensional motion analysis. The lower limb joint angle, internal joint moment, and joint power parameters on the operated side while standing were calculated. The PROMs 6 months after TKA were assessed using the Japanese Knee Osteoarthritis Measure (JKOM). The relationship between each gait biomechanical parameter and the JKOM was determined.ResultsThe maximum internal knee extension moment and maximum knee extension negative joint power during the early stance showed moderate negative correlations with the JKOM scores. The maximum internal hip abduction moment was not correlated with the JKOM scores. The maximum internal hip extension moment during the early stance and internal hip flexion moment during the late stance showed moderate negative correlations with the total JKOM scores.ConclusionThe early postoperative internal knee extension moment, maximum knee extension negative joint power, and internal hip extension and flexion moment are associated with patient PROMs 6 months after TKA.     

Inter-laboratory comparison of knee biomechanics and muscle activation patterns during gait in patients with knee osteoarthritis

BackgroundGait analysis has been used for decades to quantify knee function in patients with knee osteoarthritis; however, it is unknown whether and to what extent inter-laboratory differences affect the comparison of gait data between studies. Therefore, the aim of this study was to perform an inter-laboratory comparison of knee biomechanics and muscle activation patterns during gait of patients with knee osteoarthritis.MethodsKnee biomechanics and muscle activation patterns from patients with knee osteoarthritis were analyzed, previously collected at Dalhousie University (DAL: n = 55) and Amsterdam UMC, VU medical center (VUmc: n = 39), using their in-house protocols. Additionally, one healthy male was measured at both locations. Both direct comparisons and after harmonization of components of the protocols were made. Inter-laboratory comparisons were quantified using statistical parametric mapping analysis and discrete gait parameters.ResultsThe inter-laboratory comparison showed offsets in the sagittal plane angles, moments and frontal plane angles, and phase shifts in the muscle activation patterns. Filter characteristics, initial contact identification and thigh anatomical frame definitions were harmonized between the laboratories. After this first step in protocol harmonization, the offsets in knee angles and sagittal plane moments remained, but the inter-laboratory comparison of the muscle activation patterns improved.ConclusionsInter-laboratory differences obstruct valid comparisons of gait datasets from patients with knee osteoarthritis between gait laboratories. A first step in harmonization of gait analysis protocols improved the inter-laboratory comparison. Further protocol harmonization is recommended to enable valid comparisons between labs, data-sharing and multicenter trials to investigate knee function in patients with knee osteoarthritis.     

正走和倒走的膝关节生物力学特征比较

目的 比较正走和倒走两种不同行走模式时膝关节的生物力学特征。方法 采用三维运动捕捉系统Vicon T40和测力台AMTI OR6-7采集并比较13名健康青年男性志愿者正走和倒走时的时间、空间、运动学和动力学参数。结果 与正走相比,倒走时的步速、步频和步幅均显著减小,跨步周期和支撑相所占百分比显著增加;在矢状面上,倒走时膝关节活动度、最大屈伸力矩较正走小;在冠状面上,倒走时膝关节内翻外展活动范围也较正走小,内翻力矩峰值在支撑早期较正走小,但在支撑晚期较正走大;地面反作用力在支撑早期较正走大,但在支撑晚期较正走小。结论 倒走和正走膝关节生物力学特征差异明显。与正走相比倒走在支撑相早期能减轻膝关节内侧间室的负荷,而倒走在支撑相晚期对膝关节负荷的影响则尚须进一步研究。     

Biomechanical effects of body weight support with a novel robotic walker for over-ground gait rehabilitation

Body weight support (BWS) promotes better functional outcomes for neurologically challenged patients. Despite the established effectiveness of BWS in gait rehabilitation, the findings on biomechanical effects of BWS training still remain contradictory. Therefore, the aim of this study is to comprehensively investigate the effects of BWS. Using a newly developed robotic walker which can facilitate pelvic motions with an active BWS unit, we compared gait parameters of ten healthy subjects during a 10-m walk with incremental levels of body weight unloading, ranging from 0 to 40 % at 10 % intervals. Significant changes in joint angles and gait temporospatial parameters were observed. In addition, the results of an EMG signal study showed that the intensity of muscle activation was significantly reduced with increasing BWS levels. The reduction was found at the ankle, knee, and hip joints in the sagittal plane as well as at the hip joint in the frontal plane. The results of this study provide an important indication of increased lateral body balance and greater stabilization in sagittal and frontal plane during gait. Our findings provide a better understanding of the biomechanical effects of BWS during gait, which will help guide the gait rehabilitation strategies.     

Leg general muscle moment and power patterns in able-bodied subjects during recumbent cycle ergometry with ankle immobilization

Rehabilitation of persons with pareses commonly uses recumbent pedalling and a rigid pedal boot that fixes the ankle joint from moving. This study was performed to provide general muscle moments (GMM) and joint power data from able-bodied subjects performing recumbent cycling at two workloads.Twenty-six able-bodied subjects pedalled a stationary recumbent tricycle at 60 rpm during passive cycling and at two workloads (low 15 W and high 40 W per leg) while leg kinematics and pedal forces were recorded. GMM and power were calculated using inverse dynamic equations.During the high workload, the hip and knee muscles produced extensor/flexor moments throughout the extensions/flexions phases of the joints. For low workload, a prolonged (crank angle 0–258°) hip extension moment and a shortened range (350–150°) of knee extension moment were observed compared to the corresponding extension phases of each joint. The knee and hip joints generated approximately equal power. At the high workload the hip and knee extensors generated increased power in the propulsion phase.For the first time, this study provides GMM and power patterns for able-bodied subjects performing recumbent cycling with an immobilized ankle. The patterns showed greater similarities to upright cycling with a free ankle, than previously supposed.     

Relationship between kinematic gait parameters during three gait modifications designed to reduce peak knee abduction moment

PurposeGait modifications designed to change a single kinematic parameter have reduced first peak internal knee abduction moment (PKAM). Prior research suggests unintended temporospatial and kinematic changes occur naturally while performing these modifications. We aimed to investigate i) the concomitant kinematic and temporospatial changes and ii) the relationship between gait parameters during three gait modifications (toe-in, medial knee thrust, and trunk lean gait).MethodsUsing visual real-time biofeedback, we collected 10 trials for each modification using individualized target gait parameters based on participants’ baseline mean and standard deviation. Repeated measures ANOVA was performed to determine significant differences between conditions. Mixed effects linear regression models were then used to estimate the linear relationships among variables during each gait modification. All modifications reduced KAM by at least 5%.ResultsModifications resulted in numerous secondary changes between conditions such as increased knee abduction during toe-in gait and increased knee flexion with medial knee thrust. Within gait modifications, relationships between kinematic parameters were similar for toe-in gait and medial knee thrust (i.e. increased toe-in and decreased knee abduction), while increased trunk lean showed no relationship with any other kinematic parameters during trunk lean trials.ConclusionTwo main mechanisms were found as a result of this investigation; the first being a pattern of toeing-in, knee abduction, flexion, and internal hip rotation, while trunk lean modification presented as a separate gait pattern with limited secondary changes. Future studies should consider providing feedback on multiple linked parameters, as it may feel more natural and optimize KAM reductions.     

Modeling initial contact dynamics during ambulation with dynamic simulation

Ankle-foot orthoses are frequently used interventions to correct pathological gait. Their effects on the kinematics and kinetics of the proximal joints are of great interest when prescribing ankle-foot orthoses to specific patient groups. Mathematical Dynamic Model (MADYMO) is developed to simulate motor vehicle crash situations and analyze tissue injuries of the occupants based multibody dynamic theories. Joint kinetics output from an inverse model were perturbed and input to the forward model to examine the effects of changes in the internal sagittal ankle moment on knee and hip kinematics following heel strike. Increasing the internal ankle moment (augmentation, equivalent to gastroc-soleus contraction) produced less pronounced changes in kinematic results at the hip, knee and ankle than decreasing the moment (attenuation, equivalent to gastroc-soleus relaxation). Altering the internal ankle moment produced two distinctly different kinematic curve morphologies at the hip. Decreased internal ankle moments increased hip flexion, peaking at roughly 8% of the gait cycle. Increasing internal ankle moments decreased hip flexion to a lesser degree, and approached normal at the same point in the gait cycle. Increasing the internal ankle moment produced relatively small, well-behaved extension-biased kinematic results at the knee. Decreasing the internal ankle moment produced more substantial changes in knee kinematics towards flexion that increased with perturbation magnitude. Curve morphologies were similar to those at the hip. Immediately following heel strike, kinematic results at the ankle showed movement in the direction of the internal moment perturbation. Increased internal moments resulted in kinematic patterns that rapidly approach normal after initial differences. When the internal ankle moment was decreased, differences from normal were much greater and did not rapidly decrease. This study shows that MADYMO can be successfully applied to accomplish forward dynamic simulations, given kinetic inputs. Future applications include predicting muscle forces and decomposing external kinetics.     

Influence of the instrumented force shoe on gait pattern in patients with osteoarthritis of the knee

Osteoarthritis (OA) of the knee is associated with alterations in gait. As an alternative to force plates, instrumented force shoes (IFSs) can be used to measure ground reaction forces. This study evaluated the influence of IFS on gait pattern in patients with knee OA. Twenty patients with knee OA walked in a gait laboratory on IFS and control shoes (CSs). An optoelectronic system and force plate were used to perform 3D gait analyses. A comparison of temporal-spatial gait parameters, kinematics, and kinetics was made between IFS and CS. Patients wearing IFS showed a decrease in walking velocity and cadence (8%), unchanged stride length, an increase in stance time (13%), stride time (11%) and step width (14%). No differences were found in knee adduction moment or knee kinematics. Small differences were found in foot and ankle kinematics (2–5°), knee transverse moments (5%), ankle frontal (3%) and sagittal moments (1%) and ground reaction force (1–6%). The gait of patients with knee OA was only mildly influenced by the IFS, due to increased shoe height and weight and a change in sole stiffness. The changes were small compared to normal variation and clinically relevant differences. Importantly, in OA patients no effect was found on the knee adduction moment.     

Effect of walking with a modified gait on activation patterns of the knee spanning muscles in people with medial knee osteoarthritis

ObjectiveTo evaluate muscle activation patterns and co-contraction around the knee in response to walking with modified gait patterns in patients with medial compartment knee-osteoarthritis (KOA).Design40 medial KOA patients walked on an instrumented treadmill. Surface EMG activity from seven knee-spanning muscles (gastrocnemius, hamstrings, quadriceps), kinematics, and ground reaction forces were recorded. Patients received real-time visual feedback on target kinematics to modify their gait pattern towards three different gait modifications: Toe-in, Wider steps, Medial Thrust. The individualized feedback aimed to reduce their first peak knee adduction moment (KAM) by ≥ 10%. Changes in muscle activations and medial/lateral co-contraction index during the loading response phase (10–35% of the gait cycle) were evaluated, for the steps in which ≥ 10% KAM reduction was achieved.ResultsData from 30 patients were included in the analyses; i.e. all who could successfully reduce their KAM in a sufficient number of steps by ≥ 10%. When walking with ≥ 10% KAM reduction, Medial Thrust gait (KAM − 31%) showed increased flexor activation (24%), co-contraction (17%) and knee flexion moment (35%). Isolated wider-step gait also reduced the KAM (− 26%), but to a smaller extent, but without increasing muscle activation amplitudes and co-contraction. Toe-in gait showed the greatest reduction in the KAM (− 35%), but was accompanied by an increased flexor activation of 42% and hence an increased co-contraction index.ConclusionGait modifications that are most effective in reducing the KAM also yield an increase in co-contraction, thereby compromising at least part of the effects on net knee load.     

Contributions of muscles and external forces to medial knee load reduction due to osteoarthritis braces

BackgroundBraces for medial knee osteoarthritis can reduce medial joint loads through a combination of three mechanisms: application of an external brace abduction moment, alteration of gait dynamics, and reduced activation of antagonistic muscles. Although the effect of knee bracing has been reported independently for each of these parameters, no previous study has quantified their relative contributions to reducing medial knee loads.MethodsIn this study, we used a detailed musculoskeletal model to investigate immediate changes in medial and lateral loads caused by two different knee braces: OA Assist and OA Adjuster 3 (DJO Global). Seventeen osteoarthritis subjects and eighteen healthy controls performed overground gait trials in unbraced and braced conditions.ResultsAcross all subjects, bracing reduced medial loads by 0.1 to 0.3 times bodyweight (BW), or roughly 10%, and increased lateral loads by 0.03 to 0.2 BW. Changes in gait kinematics due to bracing were subtle, and had little effect on medial and lateral joint loads. The knee adduction moment was unaltered unless the brace moment was included in its computation. Only one muscle, biceps femoris, showed a significant change in EMG with bracing, but this did not contribute to altered peak medial contact loads.ConclusionsKnee braces reduced medial tibiofemoral loads primarily by applying a direct, and substantial, abduction moment to each subject's knee. To further enhance brace effectiveness, future brace designs should seek to enhance the magnitude of this unloader moment, and possibly exploit additional kinematic or neuromuscular gait modifications.     

Open-loop position control of the knee joint using electrical stimulation of the quadriceps and hamstrings

The clinical acceptability of functional electrical stimulation (FES) as an aid for restoration of paraplegic gait is limited by the inability to accurately and repeatedly position the lower extremity. To gain insight into the causes of and possible solutions to this problem, the responses of the quadriceps and hamstrings to FES were studied in able-bodied subjects. Isometric torque was dependent on knee angle and changed unpredictably with time. An open-loop feedforward knee-joint position controller was also tested. The results demonstrated that it is beneficial to account for the dependence of torque on position, that modifications to this openloop controller might improve accuracy and that closed-loop control may be essential for functional restoration of gait.     

慢跑的速度对青年女性下肢关节及肌肉的影响

目的 探讨合理的慢跑速度对体形和步姿的影响,使人在慢跑健身的同时兼得柔美的体态。方法 根据相关测量选择5种慢跑速度。利用运动捕捉系统采集研究对象(15位青年女性志愿者)在慢跑速度下的运动学数据,同时对下肢8块主要肌肉的肌电信号进行采集。计算获得在不同慢跑速度下髋、膝及踝关节矢状面的关节角度变化的均值。选择数据最接近均值的对象作为研究对象并进行运动学分析。结果 计算获得了该研究对象在不同慢跑速度下髋、膝及踝关节矢状面的关节角度以及下肢8块主要肌肉的激活度曲线。运用打分的方法,本文给出了研究对象慢跑速度、慢跑阶段、肌肉激活度与关节角度之间的关系。结论 各关节角的变化范围和各肌肉最大激活度并不随慢跑速度的变化而单调变化。本文为青年女性健身时选择适合自己的慢跑速度提供了参考。     

Effects of severity of degeneration on gait patterns in patients with medial knee osteoarthritis

This study tested the hypothesis that patients with mild and severe medial knee osteoarthritis (OA) adopt different compensatory gait patterns to unload the deseased knee, in not only the frontal plane but also the sagittal plane. Fifteen patients with mild and 15 with severe bilateral medial knee OA, and 15 normal controls walked while the kinematic and kinetic data were measured. Compared to the normal group, both OA groups had significantly greater pelvic anterior tilt, swing-pelvis list, smaller standing knee abduction, as well as smaller standing hip flexor and knee extensor moments during stance. The severe group also had greater hip abduction, knee extension and ankle plantarflexion. The mild group successfully reduced the extensor moment and maintained normal abductor moment at the diseased knee mainly through listing and anterior tilting the pelvis. With extra compensatory changes at other joints and increased hip abductor moment, the severe group successfully reduced the knee extensor moment but failed to reduce the abductor moment. These results suggest that, apart from training of the knee muscles, training of the hip muscles and pelvic control are essential in the rehabilitative intervention of patients with knee OA, especially for more severe patients.     

痉挛型脑瘫患者功能性选择性脊神经后根切断术前后的三维步态特征分析

目的分析痉挛型脑瘫患者功能性选择性脊神经后根切断(functional selective posterior rhizotomy,FSPR)手术前后的步态特征,客观量化评估手术疗效。方法选取15名将要进行FSPR手术治疗的痉挛型脑瘫患者,应用VICON三维运动捕捉系统结合AMTI三维测力台对患者进行手术前后的步态采集,分析手术前后步态的时空、运动学及动力学参数。结果手术后,左、右支撑时间均大于手术前,左侧步长明显大于手术前,步高、步速及冠状面重心偏移均小于手术前;着地时的膝关节矢状面角度(即屈伸角度)出现明显提高,髋、踝关节未见明显差异。手术后,步行过程中左右侧髋、膝、踝关节活动范围(range of motion,ROM)在矢状面均出现不同程度的提高,且有统计学差异;右踝关节冠状面ROM也出现明显提高。手术后,右膝关节最小屈曲角度及左、右踝关节最大跖屈角度均出现显著减小;左、右侧支撑相最大垂直力较手术前明显提高,而下肢关节力矩未见明显差异。结论三维步态分析可以在一定程度上评估痉挛型脑瘫患者FSPR手术的疗效。术后痉挛型脑瘫患者的痉挛得到缓解,对步态的时空参数及下肢关节运动学参数改善比较明显,而对于动力学参数改善相对不明显,需进行进一步康复治疗。     

Relationship between leg extensor muscle strength and knee joint loading during gait before and after total knee arthroplasty

ObjectiveThe aim of the present study was to evaluate an isometric maximal voluntary contraction (MVC) force of the leg extensor muscles and its relationship with knee joint loading during gait prior and after total knee arthroplasty (TKA).MethodsCustom-made dynamometer was used to assess an isometric MVC force of the leg extensor muscles and 3-D motion analysis system was used to evaluate the knee joint loading during gait in 13 female patients (aged 49–68 years) with knee osteoarthritis. Patients were evaluated one day before, and three and six months following TKA in the operated and non-operated leg.ResultsSix months after TKA, MVC force of the leg extensor muscles for the operated leg did not differ significantly as compared to the preoperative level, whereas it remained significantly lower for the non-operated leg and controls. The knee flexion moment and the knee joint power during mid stance of gait was improved six months after TKA, remaining significantly lowered compared with controls. Negative moderate correlation between leg extensor muscles strength and knee joint loading for the operated leg during mid stance was noted three months after TKA.ConclusionsThe correlation analysis indicates that due to weak leg extensor muscles, an excessive load is applied to knee joint during mid stance of gait in patients, whereas in healthy subjects stronger knee-surrounding muscles provide stronger knee joint loading during gait.Level of Evidence: III (correlational study)