When performing high knee flexion movements (>120º), thigh-calf (TC) and heel-gluteal (HG) structures come into contact and transmit force between segments. Previous work has only assessed the effect of these forces on net external knee joint forces and moments in the sagittal plane. Therefore, the purpose of this study was to quantify the effect of incorporating the 3D location and orientation of TC and HG force vectors on external forces and moments acting on the knee. Sixteen participants (8 M/F) completed five repetitions of six high-flexion movements. Kinematics, kinetics, and pressure distribution (of TC and HG contact) were measured from the right lower limb. Inverse dynamics were calculated with and without TC and HG force, to determine the change in magnitude. During high knee flexion movements, there was a significant reduction in AP forces (~50%) and F/E moments (~27%) as a result of considering contact between lower limb segments. Novel to this study was the ability to account for the 3D force vector and CoF location of TC and HG by tracking the motion of the pressure mat allowing the effect on frontal plane moments to be determined. There was a significant increase in the Ab/Ad moment (~60% in two movements) which is a known risk factor for knee osteoarthritis development. These results will improve the biofidelity of future high flexion musculoskeletal models of the knee. Future work is required to determine if findings from this young and healthy population translates to occupational or individuals that habitually kneel.
INTRODUCTION:Previous studies have reported that men and women demonstrate distinctly different biomechanics during running and that older runners use a variety of biomechanical adaptations compared with younger runners. It is hypothesized that excessive asymmetry due to biomechanical and anatomical abnormalities contributes to increased risk of injuries, however it is still unclear how age and gender might impact this.METHODS: A cross sectional study was employed and healthy recreational runners were categorized into four groups based on age and gender.Two-way multivariate analysis of variance was performed with age and gender as factors and Symmetry Angle values for peak hip adduction angle (HA), peak knee adduction moment (KAM), peak knee flexion angle (KF), and peak vertical ground reaction force (VGRF) were used as the dependent variables. RESULTS: Overall, gender had a significant effect on HA asymmetry (p=0.02) and both gender and age showed a significant interaction effect on KAM asymmetry (p=0.04).CONCLUSIONS:This study suggests that interlimb asymmetry in running gait for KAM and HA also differs with aging and gender.Understanding age and gender related adaptations in interlimb asymmetry will help improve running performance and develop programs aimed at reducing injury rates.
Frontal plane mechanics have been associated with running-related injuries such as patellofemoral pain. Strengthening and gait retraining programs aimed at reducing hip adduction during running have been shown to be effective at alleviating symptoms, however evidence of their effect on running kinematics is equivocal. It is possible that such programs exert their benefits through altering kinetics rather than kinematics in the frontal plane during running. Further, the contributions of the ankle to frontal plane mechanics have not been well studied. PURPOSE: To determine if hip and ankle strength are associated with frontal plane kinetics in female runners. METHODS: 64 healthy women running at least 16km per week participated in this study. Isometric hip abduction and ankle inversion strength were measured using a handheld dynamometer. 3D gait analysis was conducted as participants ran on an instrumented treadmill at 2.7 m/s. Participants were ranked in order of isometric strength of both the hip and ankle, and divided into tertiles of high, medium and low strength. 2-way MANOVA was used to determine the relationship between strength and peak moment, positive work and negative work in the frontal plane of the hip and the ankle. Tukey post-hoc tests were conducted where applicable (α=0.05). RESULTS: There was no significant interaction effect, or main effect of hip strength. There was a significant main effect of ankle strength on frontal plane kinetics (p=0.024). Specifically, the strong ankle group compared to the weak ankle group had significantly greater magnitude of peak ankle inversion moment (0.95(0.32) vs 0.68(0.22) Nm/kg, p=0.033), hip abduction moment (-2.78(1.02) vs -1.88(0.24) Nm/kg, p=0.002) and hip frontal plane positive work (0.27(0.19) vs. 0.13(0.03) W/kg, p=0.006). CONCLUSION: Isometric ankle but not hip strength is associated with kinetics in the frontal plane during running in females. Thus ankle strength should not be overlooked in clinical evaluation and treatment of runners.
Background: Approximately 33% of the adult population in the United States is considered obese (28), which increases the risk of comorbidities such as osteoarthritis (OA) (34). The most notable feature of OA is the loss of articular cartilage within a joint, resulting in pain and physical disability (3). The association between obesity and OA is due to a combination of mechanical and metabolic factors (3). Greater weight from obesity adds stress to articular cartilage in weight-bearing joints, and contributes to cartilage breakdown (21). Previous studies have demonstrated an association between gait biomechanics and OA in older populations (15, 25), but data are lacking in young obese individuals without OA. Young obese compared to normal weight adults have lesser knee flexion excursion (KFE) (31), and greater vertical loading rates (vLR) during gait (30, 31). However, the source of aberrant gait mechanics in obese adults is unclear, and could be related to impaired shock attenuation from weakened musculature in the lower extremity. Obese young adults have deficits in quadriceps function after normalizing to fat-free mass, and walk slower compared to normal weight young adults. RTD was moderately associated with KEM at habitual gait speed, and KEM was also lesser in obese compared to normal weight adults. The lesser KEM in the obese group suggests that obese young adults walk with a quadriceps avoidance gait, which may contribute to knee OA development. Exercise interventions targeting RTD may be useful for improving walking mechanics in obese adults.
Lateral ankle sprains, caused by rapid ankle inversion, and noncontact anterior cruciate ligament (ACL) knee injuries, caused by excessive knee loading, are among the most common lower extremity injuries that occur during dynamic tasks, such as cutting. Ankle braces are commonly used to prevent lateral ankle sprains by reducing ankle inversion. There is limited and conflicting research about how an ankle brace affects other joints, such as the knee, during cutting movements. It is also not known if sex differences exist during a cutting task when an ankle brace is present. The purpose of this study was to determine the effects of an Ultra Zoom® hinged ankle brace and sex on ankle and knee biomechancis during a cutting maneuver. Eighteen recreationally active adults completed sidestep cutting trials with and without an Ultra Zoom® ankle brace. Three-dimensional ankle and knee kinematics and GRF were collected. Separate 2×2 (sex × brace) repeated measures ANOVAs were used. Results indicated the brace reduced frontal plane ankle kinematics and had no effect on knee kinematics. Additionally, females demonstrated decreased knee flexion compared to males. An ankle brace during a cutting maneuver restricted frontal plane ankle movement. Furthermore, the only significant changes in knee mechanics were due to sex differences, which has been well documented. These findings indicate that the use of an Ultra Zoom® hinge brace is suitable for sports, reduces the risk of lateral ankle injuries, and does not alter knee mechanics, and therefore may not increase the risk of ACL injury.
Robotic testing was performed with a 6-degree of freedom load cell in order to analyze functional contributions of the soft tissues in the knee under physiologically relevant loading conditions. Age groups ranging from 1.5 months to 18 months, porcine equivalent to early youth through late adolescent human ages, were studied. Complete ACL transection resulted in increased APTT and VVR across all ages (p<0.05), while injury to the AM bundle did not affect APTT or VVR. Additionally, increasing age resulted in decreased APTT normalized to the tibial plateau (p<0.05) and an average 19° decrease in VVR across states from 0 to 18 months of age (p<0.05). The ACL was the primary restraint against anterior drawer in the intact knee state [75-111%]. Following AM bundle dissection, the PL bundle carried the vast majority of the anterior load regardless of age [66-112%]. Following complete ACL transection, the MCL and medial meniscus carried most of the force across ages under anterior drawer. The LCL contributed increasing resistance to varus torque across states with age, as did the MCL under valgus torque.
INTRODUCTION: Clinical interventions for foot injury prevention are often prescribed based on static measures of foot structure. However, this convention merits further investigation as the static-dynamic relationship has only been explored in walking and running. The primary aim of this study was to explore the relationship between static foot structure and dynamic midfoot kinematics and kinetics during a barefoot single-leg landing.
METHODS: 48 females (age=20.4±1.8 yr, height=1.6±0.06 m, weight=57.3±5.5 kg) completed the study. Standing arch height index (AHI) was measured using the Arch Height Index Measurement System. Skin markers were attached using a multi-segment foot model by Bruening et al.1 A14-camera motion capture system (Vicon) was used to sample kinematic data at 250Hz while two force platforms (AMTI) sampled kinetic data at 1000Hz. A static trial was captured then subjects hung from wooden rings and performed barefoot single-leg drop landings from a height of 0.4m. Metrics were calculated in Visual 3D (C-motion, Inc.) to obtain static midfoot angle (MA), midtarsal range of motion (ROM), and midtarsal work. PCCs were calculated for static and dynamic variables using paired t-tests in SAS.
RESULTS: AHI was correlated negatively with sagittal plane midtarsal ROM (r=-0.32032, p=0.0264) and positively with midtarsal work (r=0.33180, p=0.0212). MA was correlated positively with sagittal plane midtarsal ROM (r=0.48336, p=0.0005) and negatively with midtarsal work (r=-0.32321, p=0.0250).
DISCUSSION/CONCLUSION: Static foot structure may be a valuable clinical tool in assessing midfoot function relating to injury risk in athletes, who participate in high-impact loading activities, as well as in pathological populations.
Research has shown decreases in dorsiflexion ROM appear to be predictors for non-contact ACL injuries during landing tasks. The gastrocnemius-soleus complex (GSC) plays a critical role in dorsiflexion ROM, with a less compliant GSC decreasing dorsiflexion ROM. However, it is unknown whether acute GSC stretching can decrease ACL loading during landing tasks. Fifteen active participants completed three trials of single-leg drop-landings from a box. 3D-lower extremity kinematics and kinetics were captured using 3D-motion capture system and force plate. Between assessments, all participants completed a three-minute bout of stretching targeting the GSC. Musculoskeletal modeling was used to estimate ACL loading in the sagittal, frontal, and transverse planes, overall peak ACL loading, and time to peak ACL loading. Pretest and posttest ACL loading variables were compared with paired t-tests (p≤0.05). No significant differences were found between pre-stretch and post-stretch peak ACL loading time, peak frontal plane ACL loading, and peak transverse plane ACL loading (p>0.05). However, post-stretch peak sagittal plane ACL loading was significantly higher compared to pre-stretch peak sagittal plane ACL loading (p=0.008). Furthermore, overall post-stretch peak ACL loading was significantly higher compared to overall pre-stretch peak ACL loading (p=0.022). As the gastrocnemius plays a role in knee flexion, it is possible that an acute bout of stretching may increase gastrocnemius compliance, therefore increase in sagittal plane ACL loading. An increase in sagittal plane loading would also lead to an overall loading effect on the ACL. Future studies warrant investigation into the effects of chronic GSC stretching on ACL loading.
Residual stresses are known to exist in human intervertebral discs but have not been incorporated in finite element models. A multigeneration model was applied to the annulus fibrosus of the intervertebral disc to simulate residual stresses arising from growth and remodeling. The intervertebral disc shape and compressive creep were used to verify that the multigeneration approach generates realistic values of residual stress. The model was then validated by comparing its 6 degree-of-freedom mechanical response to experimental data. Human intervertebral discs were tested in a custom-built hexapod in all 6 degrees-of-freedom (lateral shear, anterior-posterior shear, torsion, bending, flexion, and compression). Incorporating residual stresses resulted in a finite element model which can predict 4 degrees-of-freedom while excluding residual stresses produces a finite element model that can only predict 2 degrees-of-freedom.
Disc function is mechanical, and measures of disc mechanical function are important to address spine function, degenerative disc disease, and low back pain. In vivo measures of disc mechanical function are needed, however the current standard in disc imaging is to acquire a single static image and classify the disc’s appearance using qualitative integer scales for degree of degeneration. Current grading standards are acknowledged as insufficient to identify symptomatic discs for treatment. In addition, static T2 weighted MRI cannot provide mechanical function information – mechanics must be measured as the change following a load or deformation perturbation. Because the disc experiences significant compression and height loss throughout the day, and because flexion-extension postures are often associated with low back pain, these physiological mechanical perturbations have potential to be used to quantify disc mechanics in vivo. The objective of this study was to use MRI-based methods to quantify in vivo disc function by measuring changes in disc geometry and T2 relaxation time with diurnal changes and with controllable posture. Quantification of in vivo disc mechanics by using diurnal loading or prescribed posture changes has potential to improve our ability to identify, evaluate, and treat degenerative disc disease. Symptomatic discs may have aberrant mechanics; if so, in vivo measurements of mechanical function may, with continued development, facilitate diagnosis of pathological discs.