Knee biomechanical factors associated with patellofemoral pain in recreational runners

BackgroundPatellofemoral pain (PFP) is a common injury among runners. Knee biomechanical factors associated with PFP, however, remain unclear. The purpose of this study was to determine possible associations between knee biomechanics and symptoms of PFP in recreational runners.MethodsFifteen male and 15 female recreational runners with PFP were enrolled as the PFP group, 30 matched runners without PFP were recruited as the control group. The PFP group was tested running with and without knee pain, while the control group had only one running test. Reflective marker coordinates and ground reaction force data were collected in each test. Knee kinematics and kinetics during running were reduced and compared between groups (PFP group without knee pain and control group) and between pain conditions (PFP group with knee pain and without knee pain), as well as between sexes.ResultsFemale and male participants with PFP had an increased peak knee valgus angle when running without pain compared to matched controls (P = 0.001), and to themselves when running with pain (P = 0.001). Male participants with PFP also had an increased peak knee flexion angle when running without pain compared to matched controls (P = 0.008), however did not decrease their peak knee flexion angle when running with pain (P = 0.245). No significant main effect of group or pain condition on any peak knee joint moment during running was detected (P ≥ 0.175).ConclusionsIncreased peak knee valgus angle during running appears to be a critical biomechanical factor associated with PFP in recreational runners, while decreasing knee valgus angle during running may be an adaptation to reduce symptoms of PFP. Increased peak knee flexion angle during running appears to be another biomechanical factor associated with PFP that is sex specific for male recreational runners.     

髌股关节痛业余跑者性别特异的下肢生物力学特征

目的 研究髌股关节痛（patellofemoral pain,PFP）业余跑者性别特异的下肢生物力学特征。方法 选取15名男性和10名女性PFP业余跑者作为实验组,并匹配25名无损伤业余跑者作为对照组。采集所有受试者跑步时的下肢运动学、动力学和表面肌电数据。采用双因素方差分析确定组别与性别对跑步时下肢生物力学特征的影响。结果 男性PFP业余跑者跑步缓冲期最大膝屈角度显著大于对照组;男性和女性PFP业余跑者跑步缓冲期最大髋内收角度显著大于对照组,且女性显著大于男性。结论 不同性别PFP业余跑者在跑步时表现出不同的下肢生物力学特征,PFP临床治疗应具有性别特异性。     

A mathematical modelling study investigating the influence of knee joint flexion angle and extension moment on patellofemoral joint reaction force and stress

BackgroundPatellofemoral pain (PFP) is the most common orthopaedic condition among runners. Individuals with PFP exhibit greater patellofemoral joint (PFJ) reaction force and stress when compared with pain-free controls. However, it is not clear whether PFJ reaction force and stress are the highest (or lowest) when knee joint flexion angle and extension moment are in which combinations. We aimed to investigate the influence of knee joint flexion angle and extension moment on PFJ reaction force and stress.MethodsA PFJ sagittal model was used to quantify PFJ reaction force and stress. Based on the public dataset of the previous study, peak knee joint flexion angle and extension moment at various running speeds was calculated. Based on the calculated peak value, simulation ranges were set to knee joint flexion angle of 10–45° and extension moment of 0–240 Nm. The quadriceps force, effective lever arm length at quadriceps muscle, and PFJ contact area were determined as a function of the knee joint flexion angle and extension moment, and finally PFJ forces and stress were estimated.ResultsPFJ reaction force increased as the knee flexion angle and extension moment increased. Although PFJ stress also increased as the knee extension moment increased, it was at the highest and lowest at 10° and about 30° knee joint flexion angles, respectively.ConclusionsIncorporating knee flexion posture (approximately 30°) during running may help in reducing PFJ stress, which would be useful in the prevention of pain and act as an optimal treatment program for PFP.     

Influence of the Powers™ strap on pain and lower limb biomechanics in individuals with patellofemoral pain

BackgroundAbnormal biomechanics, especially hip internal rotation and adduction are known to be associated with patellofemoral pain (PFP). The Powers? strap was designed to decrease hip internal rotation and to thereby stabilise the patellofemoral joint.ObjectivesThis study aimed to investigate whether the Powers? strap influenced pain and lower limb biomechanics during running and squatting in individuals with PFP.MethodsTwenty-four individuals with PFP were recruited using advertisements that were placed at fitness centres. They were asked to perform a single leg squat task (SLS) and to run on an indoor track at their own selected speed during two conditions: with and without the Powers? strap. Immediate pain was assessed with the numeric pain rating scale. Three-dimensional motion and ground reaction force data were collected with 10 Qualisys cameras and three AMTI force plates.ResultsImmediate pain was significantly reduced with the Powers? strap (without the Powers? strap: 4.04 ± 1.91; with the Powers? strap: 1.93 ± 2.13). The Powers? strap condition significantly increased hip external rotation by 4.7° during the stance phase in running and by 2.5° during the single leg squat task. Furthermore, the external knee adduction moment during the SLS and running increased significantly.ConclusionThis study assessed the effect of the Powers? strap on lower limbs kinematics and kinetics in individual with PFP. The results suggest that the Powers? strap has the potential to improve abnormal hip motion. Furthermore, the Powers? strap demonstrated an ability to significantly reduce pain during functional tasks in patients with PFP.     

弯道跑对下肢髌股关节应力的影响

目的 探究在较慢跑速下,相较于直道跑,弯道跑时两侧下肢髌股关节应力变化,分析长时间弯道跑增加髌股关节痛的可能性。方法 利用Newtest便携测速系统、Motion红外高速运动捕捉系统和Kistler三维测力台,采集13名普通男性大学生（无运动专项）以(4.0±0.2) m/s速度分别沿直道和弯道（内径为36 m）跑步时三维步态参数及地面反作用力。结果 相较于直道跑,弯道跑时外侧腿髌股关节应力增大。弯道跑髌股关节压力变化时未见膝关节屈曲角度和膝关节伸展力矩的显著变化。结论 长时间弯道跑会增加外侧腿患髌股关节痛以及加剧髌股关节痛患者疼痛感,建议跑步爱好者和髌股关节痛患者尽量避免重复长时间弯道跑。     

A comparison of tibiofemoral and patellofemoral alignment during a neutral and valgus single leg squat: an MRI study

BackgroundThe etiology of anterior knee pain is not well understood. Recently, excessive hip adduction and internal rotation have been cited as possible factors. However, how these altered hip mechanics affect the patellofemoral joint is still unclear.ObjectiveTo compare the three-dimensional tibiofemoral and patellofemoral alignment between a neutral squat and one performed with increased hip adduction and internal rotation. We aimed to examine the relationships between the three-dimensional tibiofemoral and patellofemoral alignment during a neutral and valgus squat. Finally, we aimed to determine the relationship between two-dimensional and three-dimensional measures of patellofemoral alignment.Methods10 healthy subjects were recruited for this study. Knee and patellar kinematics in a neutral squat and one performed with hip adduction and internal rotation were measured using a open, upright, magnetic resonance imaging unit. Both single leg squats were performed at 30° of knee flexion.ResultsThere was a significant correlation between knee external rotation and lateral patellar translation, and between knee abduction and lateral patellar translation. Moderate relationships were found between the 2D and 3D measures but these were not statistically significant.ConclusionThe valgus squat resulted in greater knee external rotation in all subjects. Although mean patellar mechanics were not different in the valgus squat, lateral patellar translation increased as knee external rotation increased. Lastly, 2D measures of patellofemoral alignment only provide moderately fair surrogates for 3D measures.     

Knee valgus angle during single leg squat and landing in patellofemoral pain patients and controls

BackgroundPatellofemoral pain (PFP) is a commonly presenting disorder of the lower limb, frequently effecting young physically active individuals particularly females. The condition has been associated with poor control of limb alignment while undertaking unilateral limb loading tasks. This poor alignment of the limb is believed to alter loading stress within the patellofemoral joint. This study aims to investigate the degree of knee valgus, assessed as 2D frontal plane projection angle (FPPA) during single leg squatting (SLS) and hop landing (SLL) tasks in patients with PFP and compare their performance to controls and the uninjured limb.MethodTwelve female subjects with unilateral PFP formed the patient group and thirty asymptomatic females formed the control group. They had their 2D frontal plane projection angle (FPPA) assessed during single leg squatting (SLS) and hop landing (SLL) tasks.ResultsIn the asymptomatic control group the mean FPPA for SLS was 8.4 ± 5.1° and SLL had a mean FPPA of 13.5 ± 5.7°. In the PFP group the mean FPPA for SLS was 16.8 ± 5.4° and SLL had a mean FPPA of 21.7 +/− 3.6°, these differences were significant (p < 0.01) for both tasks.ConclusionPatients with PFP have a greater degree of knee valgus on unilateral limb loading task than either their contralateral asymptomatic limb or an asymptomatic control group. If not corrected this may lead to further PFJ stress and ongoing morbidity.     

Trunk and Lower Extremity Kinematics During Stair Descent in Women With or Without Patellofemoral Pain

Context

There is limited evidence indicating the contribution of trunk kinematics to patellofemoral pain (PFP). A better understanding of the interaction between trunk and lower extremity kinematics in this population may provide new avenues for interventions to treat PFP.

Objective

To compare trunk and lower extremity kinematics between participants with PFP and healthy controls during a stair-descent task.

Design

Cross-sectional study.

Setting

Research laboratory.

Patients or Other Participants

Twenty women with PFP (age = 22.2 ± 3.1 years, height = 164.5 ± 9.2 cm, mass = 63.5 ± 13.6 kg) and 20 healthy women (age = 21.0 ± 2.6 years, height = 164.5 ± 7.1 cm, mass = 63.8 ± 12.7 kg).

Intervention(s)

Kinematics were recorded as participants performed stair descent at a controlled velocity.

Main Outcome Measure(s)

Three-dimensional joint displacement of the trunk, hip, and knee during the stance phase of stair descent for the affected leg was measured using a 7-camera infrared optical motion-capture system. Pretest and posttest pain were assessed using a visual analogue scale. Kinematic differences between groups were determined using independent-samples t tests. A 2 × 2 mixed-model analysis of variance (group = PFP, control; time = pretest, posttest) was used to compare knee pain.

Results

We observed greater knee internal-rotation displacement for the PFP group (12.8° ± 7.2°) as compared with the control group (8.9° ± 4.4°). No other between-groups differences were observed for the trunk, hip, or other knee variables.

Conclusions

We observed no difference in trunk kinematics between groups but did note differences in knee internal-rotation displacement. These findings contribute to the current knowledge of altered movement in those with PFP and provide direction for exercise interventions.Key Words: anterior knee pain, knee internal rotation, neuromuscular control

Key Points

• Trunk kinematics did not differ between women with and without patellofemoral pain during stair descent.
• Women with patellofemoral pain demonstrated greater knee internal-rotation displacement during stair descent than women without patellofemoral pain.

Patellofemoral pain (PFP) is one of the most frequent chronic injuries among females.^1,2 The causes of PFP are multifactorial, with patellofemoral malalignment commonly accepted as a major contributor.^2,3 Patellofemoral malalignment increases contact pressure within the patellofemoral joint, leading to abnormal cartilage wear and ultimately degenerative changes if left untreated or if conservative treatment options fail.^4,5Lower extremity kinematics may directly influence patellofemoral contact pressure during dynamic tasks. Specifically, the motions of femoral internal rotation, femoral adduction, and knee valgus increase patellofemoral contact pressure.^3,6–8 Extensive research^3,6,9–13 has been conducted to determine alterations in lower extremity kinematics associated with PFP. Lower extremity kinematics may be influenced by other factors that, if recognized, may have a significant effect on treatment interventions for those with PFP.Although there is evidence that trunk kinematics influence lower extremity kinematics and loading,^14–16 few studies have examined trunk kinematics in participants with PFP.^17,18 The presence of aberrant trunk motion in those with PFP and its influence on lower extremity kinematics has been theorized.¹⁹ In the frontal plane specifically, it has been proposed that individuals with PFP who display hip-abductor weakness compensate by elevating the contralateral pelvis and leaning toward the stance limb. This trunk lean has the potential to alter the orientation of the ground reaction force and subsequent external moments acting on the knee in the frontal plane. In the sagittal plane, trunk flexion moves the ground reaction force vectors anteriorly to both the hip and knee joints, thereby increasing the demand of the hip extensors and decreasing the demand of the knee extensors. Decreasing the quadriceps demand decreases the compressive forces within the patellofemoral joint.¹⁹ Given that previous researchers^13,14,16 have demonstrated a relationship between trunk and lower extremity kinematics in a healthy population, it is plausible that individuals with PFP may have altered trunk kinematics that indirectly influence patellofemoral contact pressure.The primary purpose of our study was to compare trunk and lower extremity kinematics during stair descent between women with and without PFP. Our a priori hypotheses were that women with PFP would have greater trunk rotation and lateral flexion toward the stance leg and greater overall trunk flexion. Based on previously reported observations,^20–25 we also expected to observe greater hip adduction, hip internal rotation, and knee valgus in those with PFP.     

Load-dependent movement regulation of lateral stretch shortening cycle jumps

The classical stretch shortening cycle (SSC) describes sagittal joint flexion–extensions in motions like running or hopping. However, lateral movements are integral components of team sports and are associated with frontal plane joint displacements. The purpose of this study is to identify neuromuscular and kinematical mechanisms determining motor control and performance of reactive laterally conducted SSCs. Lateral jumps were performed from four distances in order to investigate the influence of lateral stretch loads on the lower extremity. Electromyographic (EMG) data of nine lower extremity muscles were collected. Foot, ankle, knee, and hip kinematics were recorded by 3-D motion analysis. High stretch loads were characterized by a greater foot exorotation during the initial phase of contact. In the sagittal plane knee and hip joint, displacements increased, whereas in the frontal plane only the hip joint displacement was significantly raised. In particular, frontal peak joint moments increased with stretch load. Thigh muscles’ mean pre-activity amplitude was enhanced. It was possible to detect stretch reflexes in the thigh muscles, whereas in particular the short-latency reflex (SLR) was stretch load-dependently modulated. The results of the present study suggest that the foot exorotation seems to play a decisive role in the movement control of lateral jumps. The association between exorotation and increased sagittal joint displacements may be seen as a compensation strategy to shift load from the frontal to the sagittal plane. Lateral load compensation seems to strongly depend on upper leg’s kinematic and neuromuscular adjustments, rather than on the ankle joint complex.     

Erratum to: Load-dependent movement regulation of lateral stretch shortening cycle jumps

The classical stretch shortening cycle (SSC) describes sagittal joint flexion–extensions in motions like running or hopping. However, lateral movements are integral components of team sports and are associated with frontal plane joint displacements. The purpose of this study is to identify neuromuscular and kinematical mechanisms determining motor control and performance of reactive laterally conducted SSCs. Lateral jumps were performed from four distances in order to investigate the influence of lateral stretch loads on the lower extremity. Electromyographic (EMG) data of nine lower extremity muscles were collected. Foot, ankle, knee, and hip kinematics were recorded by 3-D motion analysis. High stretch loads were characterized by a greater foot exorotation during the initial phase of contact. In the sagittal plane knee and hip joint, displacements increased, whereas in the frontal plane only the hip joint displacement was significantly raised. In particular, frontal peak joint moments increased with stretch load. Thigh muscles’ mean pre-activity amplitude was enhanced. It was possible to detect stretch reflexes in the thigh muscles, whereas in particular the short-latency reflex (SLR) was stretch load-dependently modulated. The results of the present study suggest that the foot exorotation seems to play a decisive role in the movement control of lateral jumps. The association between exorotation and increased sagittal joint displacements may be seen as a compensation strategy to shift load from the frontal to the sagittal plane. Lateral load compensation seems to strongly depend on upper leg’s kinematic and neuromuscular adjustments, rather than on the ankle joint complex.     

Adding Mindfulness Practice to Exercise Therapy for Female Recreational Runners With Patellofemoral Pain: A Randomized Controlled Trial

ContextConsidering current models that highlight the role of psychological components in pain management, mindfulness practice may be an effective strategy in the management of pain.ObjectiveTo examine the effects of adding an 8-week mindfulness program to exercise therapy on the perceptions of pain severity, knee function, fear of movement, and pain catastrophizing of female recreational runners with patellofemoral pain (PFP).DesignRandomized controlled clinical trial.SettingUniversity laboratory.Patients or Other ParticipantsThirty female runners (age = 28.3 ± 7.08 years) with PFP were randomly assigned to the exercise or mindfulness-exercise group.Intervention(s)The exercise-only group followed a protocol (18 weeks, 3 sessions/wk) that featured training modifications to help control injury-related symptoms. The mindfulness-exercise group received an 8-week mindfulness intervention in addition to the exercise protocol. The mindfulness component started 4 weeks before the exercise component; therefore, the 2 components overlapped during the first 4 weeks of the intervention.Main Outcome Measure(s)Usual pain, pain during stepping, and pain during running were assessed using visual analog scales. Functional limitations of the knee were assessed using the Knee Outcome Survey. Fear of movement, pain catastrophizing, and coping strategies were measured via the Tampa Scale for Kinesiophobia, the Pain Catastrophizing Scale, and the Coping Strategies Questionnaire, respectively. These outcomes were assessed at baseline, at week 9, and after 18 weeks.ResultsPain during running, pain during stepping, and functional limitations of the knee were less for the mindfulness-exercise group than for the exercise-only group (P values < .05). The mindfulness-exercise group reported greater perceived treatment effects than the exercise-only group (P < .05). Pain catastrophizing was less and coping strategies were more favorable for mindfulness-exercise participants than for exercise-only participants (P values < .05).ConclusionsMindfulness practice can be an effective adjunct to exercise therapy in the rehabilitation of PFP in recreational female runners.     

A Contemporary Approach to Patellofemoral Pain in Runners

Patellofemoral pain (PFP) is among the most common injuries in recreational runners. Current evidence does not identify alignment, muscle weakness, and patellar maltracking or a combination of these as causes of PFP. Rather than solely investigating biomechanics, we suggest a holistic approach to address the causes of PFP. Both external loads, such as changes in training parameters and biomechanics, and internal loads, such as sleep and psychological stress, should be considered. As for the management of runners with PFP, recent research suggested that various interventions can be considered to help symptoms, even if these interventions target biomechanical factors that may not have caused the injury in the first place. In this Current Concepts article, we describe how the latest evidence on education about training modifications, strengthening exercises, gait and footwear modifications, and psychosocial factors can be applied when treating runners with PFP. The importance of maintaining relative homeostasis between load and capacity will be emphasized. Recommendations for temporary or longer-term interventions will be discussed. A holistic, evidence-based approach should consist of a graded exposure to load, including movement, exercise, and running, while considering the capacity of the individual, including sleep and psychosocial factors. Cost, accessibility, and the personal preferences of patients should also be considered.     

Subject-specific evaluation of patellofemoral joint biomechanics during functional activity

Patellofemoral joint pain is a common problem experienced by active adults. However, relatively little is known about patellofemoral joint load and its distribution across the medial and lateral facets of the patella. In this study, biomechanical experiments and computational modeling were used to study patellofemoral contact mechanics in four healthy adults during stair ambulation. Subject-specific anatomical and gait data were recorded using magnetic resonance imaging, dynamic X-ray fluoroscopy, video motion capture, and multiple force platforms. From these data, in vivo tibiofemoral joint kinematics and knee muscle forces were computed and then applied to a deformable finite-element model of the patellofemoral joint. The contact force acting on the lateral facet of the patella was 4–6 times higher than that acting on the medial facet. The peak average patellofemoral contact stresses were 8.2 ± 1.0 MPa and 5.9 ± 1.3 MPa for the lateral and medial patellar facets, respectively. Peak normal compressive stress and peak octahedral shear stress occurred near toe-off of the contralateral leg and were higher on the lateral facet than the medial facet; furthermore, the peak compressive stress (11.5 ± 3.0 MPa) was higher than the peak octahedral shear stress (5.2 ± 0.9 MPa). The dominant stress pattern on the lateral patellar facet corresponded well to the location of maximum cartilage thickness. Higher loading of the lateral facet is also consistent with the clinical observation that the lateral compartment of the patellofemoral joint is more prone to osteoarthritis than the medial compartment. Predicted cartilage contact stress maps near contralateral toe-off showed three distinctly different patterns: peak stresses located on the lateral patellar facet; peak stresses located centrally between the medial and lateral patellar facets; and peak stresses located superiorly on both the medial and lateral patellar facets.     

Evidence of Mechanical Load Redistribution at the Knee Joint in the Elderly when Ascending Stairs and Ramps

This study examined the external joint moments at the lower extremity in all three directions in a group of older and younger adults when ascending stairs and ramps. Twenty-eight older and 16 younger adults ascended a purpose-built staircase and ramp. A motion capture system and a force plate were used to determine the subjects’ 3D kinematics and ground reaction forces. Calculation of the leg kinematics and kinetics was done by means of a rigid, three-segment, 3D leg model. Older had lower dorsiflexion and knee flexion moments but higher hip flexion moments than the younger adults, independent of locomotion condition. Concerning the other two planes, older adults showed higher adduction moments at the knee and hip joint, and higher knee internal rotation moments. Furthermore, the elderly showed a more external position of the shank in relation to the thigh at the initiation of the stance phase for the two conditions examined. The higher adduction and internal rotation moments at the knee when combined with the kinematic changes in the transverse plane for the elderly give evidence that older adults redistribute the mechanical load within the load bearing regions of the knee. We concluded that the redistribution in knee joint loading may increase the risk factors for developing knee osteoarthritis in the elderly.     

女性全身关节过度活动患者跳深着陆时膝关节应力分析

目的 分析全身关节过度活动(generalized joint hypermobility, GJH)女性患者与健康女性在跳深着陆中膝关节软骨、半月板von Mises应力分布差异。方法 采集女性GJH患者与女性健康受试者在跳深着陆缓冲阶段垂直地面反作用力(vertical ground reaction force, VGRF)峰值时刻的膝关节运动学与地面反作用力特征,通过逆动力学计算膝关节反作用力,并将膝关节沿股骨长轴方向的合力作为载荷;基于1名女性膝关节三维有限元模型,分别对2组受试者跳深着陆过程进行数值仿真,计算膝关节软骨与半月板von Mises应力及应力分布。结果 在跳深着陆VGRF峰值时刻,GJH组和对照组膝关节屈曲、外翻角度具有统计学意义(P<0.05)。相比于对照组,GJH组膝关节屈曲角度降低、外翻角度增加;在跳深着陆中,GJH组膝关节内部承受应力更大且胫股关节内、外侧室负重区应力分布不均衡,其股骨软骨外侧髁外侧、外侧胫骨软骨前部/中部外侧以及外侧半月板前角、体部外侧缘为应力集中部位。结论 女性GJH患者因膝关节活动范围增大、关节囊松弛,导致在跳跃类项目中膝关节...     

Patellofemoral forces after total knee arthroplasty: effect of extensor moment arm

Total knee arthroplasty implant designs with larger extensor moment arms theoretically should generate lower extensor forces for the same externally applied loads. This study measured knee kinematics, quadriceps forces, and patellofemoral forces under conditions of dynamic knee extension under load in two knee designs with differing quadriceps moment arms. Six human cadaver knees were tested both before implantation and after sequential implantation with two posterior cruciate retaining designs. The extensor moment arm of the LMA (long extensor moment arm design, Scorpio, Howmedica Osteonics, Rutherford, NJ) was approximately 1 cm longer than that of the Control design (7000, Howmedica Osteonics). Quadriceps tension was measured during dynamic closed kinetic chain knee extension. Patellar compressive and shear forces were also recorded using a patellar component instrumented with a custom triaxial load transducer. Knee kinematics were monitored using a three-dimensional electromagnetic tracking device. Both designs produced similar patterns of femoral rollback and tibial rotation. Quadriceps tension was lower in the LMA design compared with the Control design. Patellofemoral compressive forces were also significantly reduced in the LMA design when compared with Control (8-18% lower at angles greater than 50 degrees flexion). The design with the longer extensor moment arm required less quadriceps force to extend the knee under load and reduced patellofemoral compressive forces. Reduced quadriceps forces may facilitate postoperative rehabilitation and activities such as stair climbing. Reduction in patellofemoral forces could reduce patellar complications such as anterior knee pain, component wear, and loosening.     

正常膝关节和人工膝关节髌股关节高屈曲运动特性及其比较分析

目的　分析人体正常膝关节和人工膝关节高屈曲活动下髌股关节的运动, 为膝关节髌股关节运动特性研究提供参考。 方法　建立包括膝关节骨组织和主要软组织在内的正常膝关节以及人工膝关节的动态有限元模型,采用三束股四头肌肌力非同步变力加载的方式,对膝关节下蹲运动中髌股关节的运动特性进行研究,并与相关研究结果进行对比分析。 结果　通过有限元分析,获得高屈曲膝关节三维运动的相对运动参数。髌股关节在位移和旋转均呈现出相同的运动趋势,同时,存在局部的差异,在低屈曲时, 人工髌股关节表现出先外倾后内倾的运动趋势,而正常髌股关节表现出持续内倾的运动特性。 结论　通过仿真和对比分析,人体髌股关节的运动数据总体趋势近似,同时存在差异。 对于正常膝关节,差异的原因主要在于髌骨运动各个方向上和不同屈曲度时的约束程度的改变;对于人工膝关节,差异主要来源于膝关节型面和结构的改变,以及坐标系定义、在体和离体差异、负荷加载差异。     

髋外展肌疲劳对不同性别人群单腿侧跳落地时神经肌肉控制的影响

目的 比较髋外展肌疲劳对不同性别人群单腿侧跳落地期间的姿势稳定性及其神经肌肉控制的影响。方法 比较20名男性和20名女性在髋外展肌疲劳干预前后进行单腿侧跳落地期间的压力中心(center of pressure, COP)、地面反作用力(ground reaction force, GRF)、下肢运动学、关节力矩、肌肉活动度等。结果 疲劳后,男性和女性COP在冠状面的最大位移和平均速度增加,髋关节外展峰值角度和踝关节外翻峰值角度增加,踝关节内翻峰值力矩增加。触地前200 ms,男性股直肌、股二头肌、胫前肌、腓骨长肌的激活小于女性;触地后200 ms,男性股二头肌激活小于女性。结论 髋外展肌疲劳导致冠状面姿势稳定性下降,髋、踝关节冠状面稳定性下降,可能增加关节损伤风险。不同性别人群的姿势调控策略存在差异,提示下肢关节损伤机制的性别差异值得进一步探究。     

两种疲劳方案对落地时下肢运动学和冲击力时频特征的影响

目的比较两种疲劳方案对人体落地动作下肢关节运动学及冲击力时/频域特征的影响。方法选取15名优秀跑、跳类专项男性运动员,利用Vicon运动捕捉系统和Kistler三维测力台比较两种疲劳方案(恒速跑、折返跑+垂直纵跳)前后落地时矢、额状面运动学和地面反作用力(ground reaction force,GRF)时/频域特征。结果(1)两种疲劳方案均会造成髋、膝关节在矢状面上的角度减小、屈曲活动度增加,且采用跑+跳方案时踝关节屈曲活动度、膝关节最大屈曲角速度增加(P0.05),髋关节外展活动度以及髋、膝关节最大外展角速度增加(P0.05);(2)两种疲劳方案前后,冲击力时域特征均无显著差异;采用跑和跑+跳方案,分别在3.51、8.20 Hz及1.17、3.51、7.03 Hz下表现出GRF频谱振幅减小(P0.05)。结论两种疲劳方案均会导致下肢在受到落地冲击时更多采用屈曲着地方式,但跑+跳方案表现更明显且干预时间更短,从实验方法学角度更具优势。研究结果可为研究疲劳后的力特征提供进一步参考。     

Females with knee osteoarthritis use a detrimental knee loading strategy when squatting

BackgroundThe purpose of this study was to identify sex differences in lower limb kinematics, kinetics, and muscle activation patterns between individuals with osteoarthritis and healthy controls during a two-legged squat.MethodThirty OA (15 females) and 30 healthy (15 females) participants performed three 2-legged squats. Sagittal and frontal plane hip, knee, and ankle kinematics and kinetics were calculated. Two-way ANOVAs (Sex X OA Status) were used to characterize differences in squatting strategies between sexes and between those with and without knee OA.ResultsA greater decrease in sagittal hip, knee, and ankle range of motion and knee joint power was observed in the OA participants compared to the healthy controls. Females with OA had significantly reduced hip and knee adduction angles compared to the healthy females and males with OA. Females also had decreased hip power, hip flexion, and hip adduction moments and knee adduction moments compared to their male counterparts, with the greatest deficits observed in the females with OA. Females with OA also had the highest magnitude of muscle activation for the quadriceps, hamstrings, and gastrocnemius throughout the squat, while males with OA showed increased activation of the vastus lateralis and medial gastrocnemius compared to the healthy males.ConclusionsOA significantly altered biomechanics and neuromuscular control during the squat, with males employing a hip-dominant strategy, allowing them to achieve a greater lower limb range of motion.