Knee Biomechanics of Alternate Stair Ambulation Patterns

Changes in Dynamic Mean Ankle Moment Arm in Unimpaired Walking Across Speeds, Ramps, and Stairs

Understanding the natural biomechanics of walking at different speeds and activities is crucial to develop effective assistive devices for persons with lower-limb impairments. While continuous measures such as joint angle and moment are well-suited for biomimetic control of robotic systems, whole-stride summary metrics are useful for describing changes across behaviors and for designing and controlling passive and semi-active devices. Dynamic mean ankle moment arm (DMAMA) is a whole-stride measure representing the moment arm of the ground reaction impulse about the ankle joint-effectively, how "forefoot-dominated" or "hindfoot-dominated" a movement is. DMAMA was developed as a target and performance metric for semi-active devices that adjust once per stride. However, for implementation in this application, DMAMA must be characterized across various activities in unimpaired individuals. In our study, unimpaired participants walked at "slow," "normal," and "fast" self-selected speeds on level ground and at a normal self-selected speed while ascending and descending stairs and a 5-degree incline ramp. DMAMA measured from these activities displayed a borderline-significant negative sensitivity to walking speed, a significant positive sensitivity to ground incline, and a significant decrease when ascending stairs compared to descending. The data suggested a nonlinear relationship between DMAMA and walking speed; half of the participants had the highest average DMAMA at their "normal" speed. Our findings suggest that DMAMA varies substantially across activities, and thus, matching DMAMA could be a valuable metric to consider when designing biomimetic assistive lower-limb devices.

Ergonomic dual four-bar linkage knee exoskeleton for stair ascent assistance

Introduction: Robotic exoskeletons are emerging technologies that have demonstrated their effectiveness in assisting with Activities of Daily Living. However, kinematic disparities between human and robotic joints can result in misalignment between humans and exoskeletons, leading to discomfort and potential user injuries. Methods: In this paper, we present an ergonomic knee exoskeleton based on a dual four-bar linkage mechanism powered by hydraulic artificial muscles for stair ascent assistance. The device comprises two asymmetric four-bar linkage mechanisms on the medial and lateral sides to accommodate the internal rotation of the knee and address the kinematic discrepancies between these sides. A genetic algorithm was employed to optimize the parameters of the four-bar linkage mechanism to minimize misalignment between human and exoskeleton knee joints. The proposed device was evaluated through two experiments. The first experiment measured the reduction in undesired load due to misalignment, while the second experiment evaluated the device's effectiveness in assisting stair ascent in a healthy subject. Results: The experimental results indicate that the proposed device has a significantly reduced undesired load compared to the traditional revolute joint, decreasing from 14.15 N and 18.32 N to 1.88 N and 1.07 N on the medial and lateral sides, respectively. Moreover, a substantial reduction in muscle activities during stair ascent was observed, with a 55.94% reduction in surface electromyography signal. Discussion: The reduced undesired load of the proposed dual four-bar linkage mechanism highlights the importance of the adopted asymmetrical design for reduced misalignment and increased comfort. Moreover, the proposed device was effective at reducing the effort required during stair ascent.

There are unique kinematics during locomotor transitions between level ground and stair ambulation that persist with increasing stair grade

Human ambulation is typically characterized during steady-state isolated tasks (e.g., walking, running, stair ambulation). However, general human locomotion comprises continuous adaptation to the varied terrains encountered during activities of daily life. To fill an important gap in knowledge that may lead to improved therapeutic and device interventions for mobility-impaired individuals, it is vital to identify how the mechanics of individuals change as they transition between different ambulatory tasks, and as they encounter terrains of differing severity. In this work, we study lower-limb joint kinematics during the transitions between level walking and stair ascent and descent over a range of stair inclination angles. Using statistical parametric mapping, we identify where and when the kinematics of transitions are unique from the adjacent steady-state tasks. Results show unique transition kinematics primarily in the swing phase, which are sensitive to stair inclination. We also train Gaussian process regression models for each joint to predict joint angles given the gait phase, stair inclination, and ambulation context (transition type, ascent/descent), demonstrating a mathematical modeling approach that successfully incorporates terrain transitions and severity. The results of this work further our understanding of transitory human biomechanics and motivate the incorporation of transition-specific control models into mobility-assistive technology.

Trunk Biomechanics in Individuals with Knee Disorders: A Systematic Review with Evidence Gap Map and Meta-analysis

BACKGROUND

The trunk is the foundation for transfer and dissipation of forces throughout the lower extremity kinetic chain. Individuals with knee disorders may employ trunk biomechanical adaptations to accommodate forces at the knee or compensate for muscle weakness. This systematic review aimed to synthesize the literature comparing trunk biomechanics between individuals with knee disorders and injury-free controls.

METHODS

Five databases were searched from inception to January 2022. Observational studies comparing trunk kinematics or kinetics during weight-bearing tasks (e.g., stair negotiation, walking, running, landings) between individuals with knee disorders and controls were included. Meta-analyses for each knee disorder were performed. Outcome-level certainty was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE), and evidence gap maps were created.

RESULTS

A total of 81 studies investigating trunk biomechanics across six different knee disorders were included (i.e., knee osteoarthritis [OA], total knee arthroplasty [TKA], patellofemoral pain [PFP], patellar tendinopathy [PT], anterior cruciate ligament deficiency [ACLD], and anterior cruciate ligament reconstruction [ACLR]). Individuals with knee OA presented greater trunk flexion during squatting (SMD 0.88, 95% CI 0.58-1.18) and stepping tasks (SMD 0.56, 95% CI 0.13-.99); ipsilateral and contralateral trunk lean during walking (SMD 1.36; 95% CI 0.60-2.11) and sit-to-stand (SMD 1.49; 95% CI 0.90-2.08), respectively. Greater trunk flexion during landing tasks in individuals with PFP (SMD 0.56; 95% CI 0.01-1.12) or ACLR (SMD 0.48; 95% CI 0.21-.75) and greater ipsilateral trunk lean during single-leg squat in individuals with PFP (SMD 1.01; 95% CI 0.33-1.70) were also identified. No alterations in trunk kinematics of individuals with TKA were identified. Evidence gap maps outlined the lack of investigations for individuals with PT or ACLD, as well as for trunk kinetics across knee disorders.

CONCLUSION

Individuals with knee OA, PFP, or ACLR present with altered trunk kinematics in the sagittal and frontal planes. The findings of this review support the assessment of trunk biomechanics in these individuals in order to identify possible targets for rehabilitation and avoidance strategies.

TRIAL REGISTRATION

PROSPERO registration number: CRD42019129257.

Evaluation of the power deficit of elderly people during stair negotiation: Which joints should be assisted at least by an exoskeleton and with what amount?

Climbing stairs can become a daily obstacle for elderly people, and an exoskeleton can assist here. However, the exoskeletons that are designed to assist stair climbing are actuated in different ways. To find a minimal actuation configuration, we identify the assist phases by evaluating the power deficit of 11 healthy but weak elderly people (72.4 ± 2.1 years; 69-76 years; 1.67 ± 0.10 m; 74.88 ± 14.54 kg) compared to 13 younger people (24.0 ± 1.8 years; 22-28 years; 1.74 ± 0.10 m; 70.85 ± 11.91 kg) in a biomechanical study and discuss moment characteristics. Three-dimensional kinematics and ground reaction forces were collected, and kinematics, kinetics, and power characteristics of each subject for ascent and descent were calculated using inverse dynamics. Significant differences for power between both groups were assessed with statistical parametric mapping method using dynamic time warping. During ascent, the largest significant power deficit of the elderly subjects occurs in the single stance phase (SSP) during pull-up in the knee joint. During descent, significant mean power deficits of 0.2 and 0.8 W/kg for the highest deficit occur in the ankle joint in the beginning of the SSP and also in the knee joint in the same phase. Therefore, an exoskeleton should address the power deficit for knee extension (ascent: 1.0 ± 0.9 W/kg; descent: 0.3 ± 0.2 W/kg) and could assist the ankle during ascent and descent by an additional plantar flexion moment of 0.2 Nm/kg each.

Load applied on osseointegrated implant by transfemoral bone-anchored prostheses fitted with state-of-the-art prosthetic components

BACKGROUND

This study presented the load profile applied on transfemoral osseointegrated implants by bone-anchored prostheses fitted with state-of-the-art ÖSSUR microprocessor-controlled Rheo Knee XC and energy-storing-and-returning Pro-Flex XC or LP feet during five standardized daily activities.

METHODS

This cross-sectional cohort study included 13 participants fitted with a press-fit transfemoral osseointegrated implant. Loading data were directly measured with the tri-axial transducer of an iPecsLab (RTC Electronics, USA) fitted between the implant and knee unit. The loading profile was characterized by spatio-temporal gaits variables, magnitude of loading boundaries as well as onset and magnitude of loading extrema during walking, ascending and descending ramp and stairs.

FINDINGS

A total of 2127 steps was analysed. The cadence ranged between 36 ± 7 and 47 ± 6 strides/min. The absolute maximum force and moments applied across all activities was 1322 N, 388 N and 133 N as well as 22 Nm, 52 Nm and 88 Nm on and around the long, anteroposterior and mediolateral axes of the implant, respectively.

INTERPRETATION

This study provided new benchmark loading data applied by transfemoral bone-anchored prostheses fitted with selected ÖSSUR state-of-the-art components. Outcomes suggested that such prostheses can generate relevant loads at the interface with the osseointegrated implant to restore ambulation effectively. This study is a worthwhile contribution toward a systematic recording, analysis, and reporting of ecological prosthetic loading profiles as well as closing the evidence gaps between prescription and biomechanical benefits of state-of-the-art components. Hopefully, this will contribute to improve outcomes for growing number of individuals with limb loss opting for bionic solutions.

Biomechanics of Single Stair Climb With Implications for Inverted Pendulum Modeling

Step-by-step (SBS) stair navigation is used by those with movement limitations or lower-limb prosthetics and by humanoid robots. Knowledge of biomechanical parameters for SBS gait, however, is limited. Inverted pendulum (IP) models used to assess dynamic stability have not been applied to SBS gait. This study examined the ability of the linear inverted pendulum (LIP) model and a closed-form, variable-height inverted pendulum (VHIP) model to predict capture-point (CP) stability in healthy adults executing a single stair climb. A second goal was to provide baseline kinematic and kinetic data for SBS gait. Twenty young adults executed a single step onto stairs of two heights, while attached marker positions and ground reaction forces were recorded. opensim software determined body kinematics and joint kinetics. Trials were analyzed with LIP and VHIP models, and the predicted CP compared to the actual center-of-pressure (CoP) on the stair. Lower-limb joint moments were larger than those reported for step-over-step (SOS) stair gait. Leading knee rather than trailing ankle was dominant. Center-of-mass (CoM) velocity peaked at push-off. The VHIP model accounted for only slightly more than half of the forward progression of the vertical projection of the CoM and was not better than LIP predictions. This suggests that IP models are limited in modeling SBS gait, likely due to large hip and knee moments. The results from this study may also provide target values and strategies to aid design of lower-limb prostheses and powered exoskeletons.

The Influence of Carrying Anterior Load on the Sagittal and Frontal Plane Kinematics of Lower Extremities during Stair Ascending

Background:

Anterior load carriage is a one of the commonly performed activities in some industries. Stair climbing while carrying anterior load significantly alters different biomechanical mechanisms that can potentially affect the musculoskeletal function of the lower extremities.

Objective:

The study aims to assess the effect of carrying an anterior load (20% of body weight) on lower extremity kinematics during the kinematical phases of stairs ascent (weight acceptance, pull up, forward continuance, and swing phase).

Material and Methods:

In this experimental study, data were collected through the use of a custom made wooden staircase and OPtiTrack motion capture system was composed of 12 infrared cameras and a per modeled reflective marker set. Sixteen female college students volunteered to conduct two tasks of ascending stairs with and without an anterior load of approximately 20% of their body weight. The collected frontal and sagittal plane lower extremity joint angles were calculated using MATLAB software (version R2015a). Statistical comparison between the two study tasks was made using IBM SPSS Statistics software (version 25.0; SPSS Inc., Chicago, IL, USA).

Results:

Based on the results, there is significant difference (p-value < 0.05) between the two study tasks during ascending stair phases in all three sagittal plan lower extremity joint angles.

Conclusion:

Anterior load carried during stair ascent causes participants to depend more on the hip joint (higher flexion angles) compared to stair ascent without loads, which may increase the risk of falls and injuries, and the importance of muscle-strengthening activities and highlight the use of appropriate technique during load carriage.

Modularity in Motor Control: Similarities in Kinematic Synergies Across Varying Locomotion Tasks

Kinematic synergies (kSYN) provide an approach to quantify the covariation of joint motions and to explain the mechanisms underlying human motor behavior. A low-dimensional control strategy by means of the activation of a moderate number of kSYN would simplify the performance of complex motor tasks. The purpose of this study was to examine similarities between the kSYN of varying locomotion tasks: straight-line walking, walking a 90° spin turn and walking upstairs. Task-specific kSYN were extracted from full body kinematic recordings of 13 participants by principal component analysis. The first five kSYN accounting for most of the variance within each task were selected for further analysis following previous studies. The similarities between the kSYN of the three different locomotion tasks were quantified by calculating cosine similarities (SIM), as a vector-based similarity measure ranging from 0 (no similarity) to 1 (high similarity), between absolute principal component loading vectors. A SIM between two kSYN > 0.8 was interpreted as highly similar. Two to three highly similar kSYN were identified when comparing two individual tasks with each other. One kSYN, primarily characterized by anteversion and retroversion of the arms and legs, were found to be similar in all three tasks. Additional kSYN that occurred between individual tasks reflected mainly an upwards/downwards movement of the body or a countercyclical knee flexion/extension. The results demonstrate that the three investigated locomotion tasks are characterized by kSYN and that certain kSYN repeatedly occur across the three locomotion tasks. PCA yields kSYN which are in descent order according to their amount of total variance accounted for. Referring to the placing of a kSYN within the order as priorization, we found a change in priorization of repeatedly occurring kSYN across the individual tasks. The findings support the idea that movements can be efficiently performed through a flexible combination of a lower number of control-relevant variables.

Biomechanical analysis of stair ascent in persons with Chopart amputation

BACKGROUND

Compared to walking on level ground, ascending stairs requires a large range of motion not only of the hip and knee joint, but also of the ankle joint. The prosthesis often worn by persons with partial foot amputation largely prevents the ankle motion needed during stair ascent.

OBJECTIVES

Aim of this study was to assess subjects with a Chopart amputation utilizing a clamshell device during stair ascent to identify potential biomechanical deficits.

STUDY DESIGN

Cross-sectional study with reference group.

METHODS

Six subjects with unilateral Chopart amputation and 17 unimpaired subjects underwent three-dimensional motion analysis while ascending stairs in a step-over-step manner.

RESULTS

During weight acceptance, the involved side showed increased external hip-flexing and reduced knee-flexing moments and the sound side a higher ankle power than in the control group. The sound side showed higher external knee-flexing, dorsi-flexing, and hip-adducting moments than the controls during weight acceptance.

CONCLUSION

The mechanism observed on the involved side differs from that in controls, but is comparable to the mechanisms used by subjects with transtibial amputation reported in the literature. However, compensatory movements on the sound side take place at the ankle and knee joint, differing from subjects with more proximal amputations.

CLINICAL RELEVANCE

This study underpins the importance of adequate foot leverage and ankle function in cases of partial foot amputation, particularly in transfer situations such as stair ascent. If ankle range of motion is adequate, prosthetic/orthotic devices combining shank leverage with a hinged spring mechanism at the ankle may be promising.

External loading alters lower extremity kinetics, kinematics, and muscle activity in a distribution-specific manner during the transition from stair descent to level walking

BACKGROUND

Excess body mass is thought to be a major cause of altered biomechanics in obesity, but the effects of body mass distribution in biomechanics during daily living tasks are unknown. The purpose of this study was to determine how increasing body mass centrally and peripherally affects lower extremity kinematics, kinetics, and muscle activation when transitioning from stair descent to level gait.

METHODS

Fifteen normal weight volunteers descended a staircase at a self-selected pace under unloaded, centrally loaded, and peripherally loaded conditions. Spatial-temporal gait characteristics and lower extremity joint kinematics, kinetics, and mean electromyography amplitude were calculated using 3D motion analysis.

FINDINGS

Both central and peripheral loading reduced gait velocity. Peripheral loading increased time spent in stance phase, increased step width, and reduced step length. At the hip joint, peripheral loading reduced peak hip extension and adduction angle. Conversely, central loading reduced peak hip flexor moment. Both central and peripheral loading increased peak knee flexion angle, but only peripheral loading increased peak knee extensor moment. Central and peripheral loading increased mean electromyography amplitude of the medial gastrocnemius, but only peripheral loading increased mean electromyography amplitude of the semitendinosus and the vastus medialis.

INTERPRETATION

Increasing mass centrally and peripherally differently affects spatial-temporal gait characteristics and lower extremity joint kinematics, kinetics, and electromyography when transitioning from stair descent to level gait. Body mass distribution may be an important factor for obesity-induced biomechanical alterations and should be considered when developing biomechanical models of obesity.

Patients With Medial Knee Osteoarthritis Reduce Medial Knee Contact Forces by Altering Trunk Kinematics, Progression Speed, and Stepping Strategy During Stair Ascent and Descent: A Pilot Study

Medial knee loading during stair negotiation in individuals with medial knee osteoarthritis, has only been reported in terms of joint moments, which may underestimate the knee loading. This study assessed knee contact forces (KCF) and contact pressures during different stair negotiation strategies. Motion analysis was performed in five individuals with medial knee osteoarthritis (52.8±11.0 years) and eight healthy subjects (51.0±13.4 years) while ascending and descending a staircase. KCF and contact pressures were calculated using a multi-body knee model while performing step-over-step at controlled and self-selected speed, and step-by-step strategies. At controlled speed, individuals with osteoarthritis showed decreased peak KCF during stair ascent but not during stair descent. Osteoarthritis patients showed higher trunk rotations in frontal and sagittal planes than controls. At lower self-selected speed, patients also presented reduced medial KCF during stair descent. While performing step-by-step, medial contact pressures decreased in osteoarthritis patients during stair descent. Osteoarthritis patients reduced their speed and increased trunk flexion and lean angles to reduce KCF during stair ascent. These trunk changes were less safe during stair descent where a reduced speed was more effective. Individuals should be recommended to use step-over-step during stair ascent and step-by-step during stair descent to reduce medial KCF.

Performance of stair negotiation in patients with cerebral palsy and stiff knee gait

BACKGROUND

Due to the limited knee range of motion, achieving adequate foot clearance while walking on level ground constitutes a major problem for patients with cerebral palsy and stiff knee gait. Stair negotiation as an activity of daily life requires a considerably higher knee range of motion than level ground walking, but little is known yet as to whether such patients are able to walk stairs.

RESEARCH QUESTION

The aim of this study was to investigate how patients with a limited knee range of motion negotiate stairs. Do they increase their peak knee flexion and use the same pattern as in walking on level ground? How do the muscles act during stair negotiation?

METHODS

In this explorative study, 17 adults with bilateral, spastic cerebral palsy and stiff knee gait and 25 healthy subjects were examined. 3D motion analysis, including electromyography, was performed while walking on level ground, upstairs, and downstairs. A linear mixed model was used for between- and within-group comparisons.

RESULTS

Walking upstairs and downstairs, patients increased their peak knee flexion by around 30° compared to level walking. Thus, increased knee flexion may be seen as the main mechanism for maintaining foot clearance on stairs. An increased pelvic obliquity (elevation) and hip flexion were also found and involved subjects showed a slight increase in rectus femoris activity when walking on stairs compared to level walking within the phases of high knee flexion.

SIGNIFICANCE

This study showed that patients with cerebral palsy and stiff knee gait are able to flex their knees more than would be required for level walking. Hence, the patients are able to adapt their rectus activity to stair walking to some extent. Therefore, further investigations might help to open up new therapeutic options to facilitate level walking and stair negotiation in patients with stiff knee gait.

Spinal Curvature and Lower Extremities Kinematics of Simulated Pregnancy during Stair Ascending and Descending

The purpose of this work is to investigate the effect of anteriorly-added mass to simulate pregnancy on lower extremities kinematic and lumbar and thoracic angles during stair ascending and descending. 18 healthy females ascended and descended, with and without a pseudo-pregnancy sac of 12 kg (experimental and control groups, respectively), a costume-made wooden staircase while instrumented with 20 reflective markers placed on the lower extremities and the spine. The movements were captured by 12 infrared cameras surrounding the staircase. Tracked position data were exported to MATLAB to calculate the required joints angles. SPSS was used to compare the ascent and descent phases of control group, and to find if there are any significant differences between control and experimental groups in the ascent phase as well as in the descent phase. When comparing the ascent and descent phases of control group, data revealed a higher hip flexion during ascending and greater ankle planter-flexion and dorsiflexion, lumbar, and thoracic angles during descending; however, no significant difference was shown in the knee flexion angle between ascending and descending. Non-pregnant data showed greater maximum hip flexion and ankle dorsiflexion during stair ascending compared to simulated-pregnant group; while ankle planter-flexion, knee flexion, and lumbar angle were greater for simulated-pregnant status. During stair descending, non-pregnant group had greater minimum hip flexion and ankle dorsiflexion compared to simulated pregnant group; while ankle planter-flexion, knee flexion, and maximum hip flexion were greater for simulated-pregnant group. However, the lumbar and thoracic angles were found to be similar for simulated-pregnant and non-pregnant groups during stair descending. In conclusion, the current study revealed important kinematic modifications pregnant women adopt while ascending and descending stairs at their final stage of pregnancy to increase their stability.

Injury patterns of medial meniscus posterior root tears

INTRODUCTION

Medial meniscus posterior root tear (MMPRT) can occur in middle-aged patients who have a posteromedial painful popping during light activities. MMPRTs are more common in patients with increased age, female gender, sedentary lifestyle, obesity, and varus knee alignment. However, injury mechanisms of minor traumatic MMPRTs are still unclear. We hypothesized that high flexion activities are the major cause of MMPRTs. The aim of this study was to clarify injury patterns of MMPRTs.

MATERIALS AND METHODS

One hundred patients were diagnosed having MMPRTs after posteromedial painful popping episodes. Details of posteromedial painful popping episode, situation of injury, and position of injured leg were obtained from the patients by careful interviews. Injury patterns were divided into 8 groups: descending knee motion, walking, squatting, standing up action, falling down, twisting, light exercise, and minor automobile accident.

RESULTS

A descending knee motion was the most common cause of MMPRTs (38%) followed by a walking injury pattern (18%) and a squatting action related to high flexion activities of the knee (13%). The other injury patterns were less than 10%.

DISCUSSION

Descending knee motions associated with descending stairs, step, and downhill slope are the most common injury pattern of MMPRTs. High flexion activities of the knee are not the greatest cause of MMPRTs. Our results suggest that the descending action with a low knee flexion angle may trigger minor traumatic MMPRTs.

LEVEL OF EVIDENCE

IV, retrospective cohort study.

Alternate stair descent strategies for reducing joint moment demands in older individuals

Descending stairs requires elevated joint moment-generating capability in the lower limbs, making it a challenging daily activity, particularly for older individuals. The aim of the study was to investigate the influence of three different strategies for descending standard and increased height stairs: step-over-step (SoS), step-by-step (SbS) and side-step (SS) on lower limb kinetics in older people. Eleven participants (mean ± SD age: 74.8 ± 3.1 years, height: 1.63 ± 0.07 m, mass: 67.7 ± 9.5 kg) descended a four-step custom built instrumented staircase at a self-selected speed, adopting each of the three strategies, at two configurations: a step-rise height of 170 mm (standard; STD) and a step-rise height of 255 mm (increased; INC). 3D motion capture, synchronised with embedded force plates enabled the calculation of joint kinetics of lead and trail limbs. Data were analysed using a Linear Mixed Model with gait speed selected as a covariate during weight acceptance (WA) and controlled lowering (CL) phases. A large increase in hip extensor moment in both WA and CL in the lead limb was evident during both SoS and SbS at INC step height compared to STD (P < .015 for all), with no such increase in hip flexor moment evident in SS strategy (P = .519). Lead limb knee extensor moment decreased and plantarflexor moment increased in INC SoS compared to STD SoS during CL (P < .001 for both). In the trail limb, increased hip extensor and plantarflexor moments were seen in INC SS compared to STD SS (P < .001 for both). The alternate strategies result in the overall task demand being split between the lead limb (weight acceptance) and trail limb (controlled lowering). Differential demand distribution patterns exist between strategies that imply targeted interventions and/or advice could be provided to older individuals in order to promote safe descent of stairs, particularly for those with specific muscle weaknesses or at high risk of falls.

A review of stairway falls and stair negotiation: Lessons learned and future needs to reduce injury

Stairways are a common location for falls, and they result in a disproportionate risk of death or severe injury. Stairway falls are a significant problem across the lifespan and are often coincident with risky behaviors during stair use. The mechanics of successful stair negotiation for healthy young and older adults have been well described. These studies imply that current stair design does not offer an optimal universal design to meet the needs of older adults or people with health conditions. In addition, impaired stair negotiation associates with more than impaired strength, including functional impairments of cognitive load, sensory function and central motor coordination. Identification of behavioral strategies or stairway environments that assist or hinder recovery from a loss of balance on stairs remains incomplete. Therefore, future studies should investigate the mechanisms of balance recovery on stairs as well as the effectiveness of environmental interventions to mitigate stairway falls and injuries. Potential areas for evaluation may include modifying stair dimensions, surfaces, handrails, visual cues, and removing distractors of attention. Studies should also evaluate combinatorial interventions on person-related factors, such as behavioral interventions to decrease risky behaviors during stair use as well as interventions on cognitive, sensory, and motor functions relevant to stair use. Moreover, future studies should take advantage of new technologies to record stair use outside the laboratory in order to identify people or locations at risk for stairway falls. Such studies would inform the potential for broad-spectrum programs that decrease the risk of stairway falls and injuries.

Can a single lower trunk body-fixed sensor differentiate between level-walking and stair descent and ascent in older adults? Preliminary findings

Stair ascent and descent are common forms of ambulation that may be challenging to detect. Here, we propose the first step towards differentiating between stair negotiation and level-walking using a single body-fixed sensor. Seventeen healthy older adults (age: 79.3±4.2 years, 47% women) wore a body-fixed sensor on the lower-back while performing level-walking and stair negotiation. Measures derived from the 3D acceleration and angular-velocity signals included medians, ranges, step duration, step and stride regularity, filtered vertical to horizontal acceleration ratio (VAF/HAF), and wavelet-based features. Friedman's and Wilcoxon tests compared between conditions. Stepwise-binary logistic-regression evaluated classification accuracy. During level-walking, yaw range was lowest and anterior-posterior and vertical step and stride regularity were highest (p≤0.007). Anterior-posterior step regularity (p=0.003), VAF/HAF (p=0.094), and yaw range (p=0.105) identified level-walking (92.2% accuracy). During stair ascent, roll range, median anterior-posterior acceleration and anterior-posterior wavelet-coefficient were lowest (p≤0.006), while VAF/HAF was highest (p=0.0029). Anterior posterior wavelet coefficient (p=0.038) and VAF/HAF (p=0.018) identified stair ascent (94.3% accuracy). During stair descent, vertical and medio-lateral ranges were highest and medio-lateral stride regularity and VAF/HAF were lowest (p≤0.006). VAF/HAF (p=0.01), medio-lateral acceleration range (p=0.069), and medio-lateral stride regularity (p=0.072) identified stair descent (90.2% accuracy). These findings suggest that a single worn body-fixed sensor can be used to differentiate between level-walking and stair negotiation.

Influence of Total Knee Arthroplasty on Gait Mechanics of the Replaced and Non-Replaced Limb During Stair Negotiation

This study compared biomechanics during stair ascent in replaced and non-replaced limbs of total knee arthroplasty (TKA) patients with control limbs of healthy participants. Thirteen TKA patients and fifteen controls performed stair ascent. Replaced and non-replaced knees of TKA patients were less flexed at contact compared to controls. The loading response peak knee extension moment was greater in control and non-replaced knees compared with replaced. The push-off peak knee abduction moment was elevated in replaced limbs compared to controls. Loading and push-off peak hip abduction moments were greater in replaced limbs compared to controls. The push-off peak hip abduction moment was greater in non-replaced limbs compared to controls. Future rehabilitation protocols should consider the replaced knee and also the non-replaced knee and surrounding joints.

Does a microprocessor-controlled prosthetic knee affect stair ascent strategies in persons with transfemoral amputation?

BACKGROUND

Stair ascent can be difficult for individuals with transfemoral amputation because of the loss of knee function. Most individuals with transfemoral amputation use either a step-to-step (nonreciprocal, advancing one stair at a time) or skip-step strategy (nonreciprocal, advancing two stairs at a time), rather than a step-over-step (reciprocal) strategy, because step-to-step and skip-step allow the leading intact limb to do the majority of work. A new microprocessor-controlled knee (Ottobock X2(®)) uses flexion/extension resistance to allow step-over-step stair ascent.

QUESTIONS/PURPOSES

We compared self-selected stair ascent strategies between conventional and X2(®) prosthetic knees, examined between-limb differences, and differentiated stair ascent mechanics between X2(®) users and individuals without amputation. We also determined which factors are associated with differences in knee position during initial contact and swing within X2(®) users.

METHODS

Fourteen individuals with transfemoral amputation participated in stair ascent sessions while using conventional and X2(®) knees. Ten individuals without amputation also completed a stair ascent session. Lower-extremity stair ascent joint angles, moment, and powers and ground reaction forces were calculated using inverse dynamics during self-selected strategy and cadence and controlled cadence using a step-over-step strategy.

RESULTS

One individual with amputation self-selected a step-over-step strategy while using a conventional knee, while 10 individuals self-selected a step-over-step strategy while using X2(®) knees. Individuals with amputation used greater prosthetic knee flexion during initial contact (32.5°, p = 0.003) and swing (68.2°, p = 0.001) with higher intersubject variability while using X2(®) knees compared to conventional knees (initial contact: 1.6°, swing: 6.2°). The increased prosthetic knee flexion while using X2(®) knees normalized knee kinematics to individuals without amputation during swing (88.4°, p = 0.179) but not during initial contact (65.7°, p = 0.002). Prosthetic knee flexion during initial contact and swing were positively correlated with prosthetic limb hip power during pull-up (r = 0.641, p = 0.046) and push-up/early swing (r = 0.993, p < 0.001), respectively.

CONCLUSIONS

Participants with transfemoral amputation were more likely to self-select a step-over-step strategy similar to individuals without amputation while using X2(®) knees than conventional prostheses. Additionally, the increased prosthetic knee flexion used with X2(®) knees placed large power demands on the hip during pull-up and push-up/early swing. A modified strategy that uses less knee flexion can be used to allow step-over-step ascent in individuals with less hip strength.

Difference in knee rotation between total and unicompartmental knee arthroplasties during stair climbing

PURPOSE

The purpose of this study was to compare knee kinematics during stair walking in patients with simultaneous total knee arthroplasty (TKA) and unicompartmental knee arthroplasties (UKA). It was hypothesized that UKA would reproduce more normalized knee kinematics than TKA during stair ascent and descent.

METHODS

Six patients who received UKA in one knee and TKA in the other knee were included in the study. For this study, a four-step staircase was assembled with two force platforms being positioned at the centre of the second and third steps. Each patient was attached with 16 reflective markers at both lower extremities and was asked to perform five roundtrip trials of stair climbing. Kinematic parameters including stance duration, knee angle, vertical ground reaction force (GRF), joint reaction force, and moments were obtained and analysed using a10-camera motion system (VICON, Oxford, UK). Nonparametric Friedman test was used to compare the results between two arthroplasty methods and between stair ascent and descent.

RESULTS

Compared to TKA, UKA knees exhibited significantly greater degree of rotation in transverse planes (5.0 degrees during ascent and 6.0 degrees during descent on average), but showed no difference in terms of the other parameters. When comparing the results during stair ascent with descent, overall greater knee angle, vertical GRF, joint reaction force, and moment were observed during stair descent.

CONCLUSIONS

Both UKA and TKA knees have shown overall similar knee kinematics, though UKA knee may allow greater degree of rotation freedom, which resembles normal knee kinematics during stair walking.

Foot clearance strategy for step-over-step stair climbing in transfemoral amputees

BACKGROUND AND AIM

Stair ascent is a particularly challenging task for transfemoral amputees. The aim of this clinical note was to describe the kinematic features of foot clearance in transfemoral amputee who can ascend stairs using a step-over-step strategy.

TECHNIQUE

The marker trajectories of the first metatarsophalangeal joint (Mt1) and clearance height were measured in two transfemoral amputees who could (TF1) and could not (TF2) climb stairs using a step-over-step strategy.

DISCUSSION

The Mt1 marker trajectories of the TF1 moved backward in the early swing phase, and the trajectory followed an off-centered parabolic arc to achieve a similar clearance height as able-bodied subjects. TF2 could not climb the stairs without tripping in each step. An effective compensatory strategy to avoid tripping during stair climbing may be to use the hip joint for a backward extension and rapid flexion of the prosthetic leg during the early swing phase.

CLINICAL RELEVANCE

The foot clearance strategy in transfemoral amputees who can climb stairs using a step-over-step strategy will help us better understand adaptive prosthetic control and thus develop more effective gait rehabilitation programs.

The use of a lateral wedge insole to reduce knee loading when ascending and descending stairs in medial knee osteoarthritis patients

BACKGROUND

Stair climbing is a challenging task to the elderly being the task with the first complaint in patients with mild to moderate knee osteoarthritis. Stair climbing results in around six times more compressive load transmitted through the knee joint than walking on level ground. The purpose of this study was to assess whether lateral wedge insoles would reduce medial compartment knee loading when ascending and descending stairs in patients with medial knee osteoarthritis.

METHODS

Eight patients with medial knee osteoarthritis were tested in random order with and without a pair of 5° off-the-shelf lateral wedge insoles for two separate activities (stair ascent and stair descent). Kinematic and kinetic data were collected for the lower extremity using a sixteen camera motion capture system and two force plates. Primary outcome measures were the external knee adduction moment and the knee adduction angular impulse.

FINDINGS

During stair ascent and descent, lateral wedge insoles significantly (P<0.05) reduced the 1st peak external knee adduction moment in early stance (ascent 6.8%, descent 8.4%), the trough in mid stance (ascent 13%, descent 10.7%), 2nd peak in the late stance (ascent 15%, descent 8.3%) and the knee adduction angular impulse compared to the control (standard shoe) with large effect sizes (0.75-0.95).

INTERPRETATION

In this first study on stairs, lateral wedge insoles consistently reduced the overall magnitude of medial compartment loading during stair ascent and descent. Further research is needed to determine the relationship of this with clinical results when ascending and descending stairs with lateral wedge insoles.

Effect of one- vs. two-stair climb training on sprint power

Although running stairs is often used in sport conditioning programs, at present, little research has examined the effect of stair climb training on sprint power. The purpose of this study was to investigate the effects of running stairs either 1 stair (1S) or 2 stairs (2S) at a time on power. Fourteen male college track and field athletes were randomized into 3 groups; 1S, 2S, or control (C). All groups were pre- and posttested for 1S, 2S, and 40-m sprint split times. The 1S and 2S groups trained twice per week, for 4 weeks, performing 10 sets of climbing 68 total stairs with 2.5-minute rest between trials. The greatest power values (W) from pre- and poststairs and sprint splits were used for statistical analyses. There was a significant (p < 0.05) interaction of group × time for stair climb. The 1S group increased power for the 1S test (pre-1,492.89 ± 123.76; post-1,647.41 ± 73.65) with no change in the 2S test (pre-2,428.80 ± 414.81; post-2,430.32 ± 154.90), whereas the 2S group increased power for the 2S test (pre-2,343.73 ± 317.50; post-2,646.17 ± 305.43) with no change in the 1S test (pre-1,516.69 ± 210.64; post-1,529.38 ± 236.69). The C group showed no change in either stair test (1S: pre-1,403.35 ± 238.67, post-1,384.38 ± 153.32; 2S: pre-2,285.93 ± 345.03, post-2,261.85 ± 356.88). There were no significant interactions or main effects for any sprint split power (40 m: pre-5,337.13 ± 611.86, post-5,318.68 ± 586.24).Therefore, stair climb training either 1 or 2 at a time did not affect 40-m sprint split power but increased power for the specific stair training type. Coaches should choose the number of stairs that are similar in time and power output to sprint training.

Factors affecting stair-ascent patterns in unilateral transfemoral amputees

BACKGROUND

Patterns and ease of stair ambulation influence amputees' level of satisfaction with their rehabilitation, confidence level, and motivation for continued rehabilitation, demonstrating the importance of stair-ascent data for rehabilitation. However, little is known about the determinants of stair-ascent patterns in unilateral transfemoral amputees.

OBJECTIVES

To investigate the factors affecting stair-ascent patterns in transfemoral amputees.

STUDY DESIGN

Cross-sectional survey.

METHODS

Stair-ascent patterns were evaluated using the Stair Assessment Index. We collected Stair Assessment Index data as well as demographic and clinical data (sex, age, height, mass, amputation side, reason for amputation, time since amputation, and residual limb length) from 25 transfemoral amputees.

RESULTS

Statistical analyses revealed that age was negatively correlated and time since amputation was positively correlated with Stair Assessment Index. In contrast, height, body mass, and residual limb lengths were not correlated with Stair Assessment Index.

CONCLUSION

The results of this study suggest that in unilateral transfemoral amputee, (1) both age and time since amputation could affect stair-climbing patterns and (2) residual limb length should not be a limiting factor for stair climbing if the transfemoral amputee has a certain minimum residual limb length.

CLINICAL RELEVANCE

Rehabilitation teams should carefully consider nonmodifiable predisposing factors such as age and time since amputation. However, they may be able to carry on stair-ascent rehabilitation for transfemoral amputees disregarding residual limb length (depending on the length).

Do lower-extremity joint dynamics change when stair negotiation is initiated with a self-selected comfortable gait speed?

Previous research on the biomechanics of stair negotiation has ignored the effect of the approaching speed. We examined if initiating stair ascent with a comfortable self-selected speed can affect the lower-extremity joint moments and powers as compared to initiating stair ascent directly in front of the stairs. Healthy young adults ascended a custom-built staircase instrumented with force platforms. Kinematics and kinetics data were collected simultaneously for two conditions: starting from farther away and starting in front of the stairs and analyzed at the first and second ipsilateral steps. Results showed that for the first step, participants produced greater peak knee extensor moment, peak hip extensor and flexor moments and peak hip positive power while starting from farther away. Also, for both the conditions combined, participants generated lesser peak ankle plantiflexor, greater peak knee flexor moment, lesser peak ankle negative power and greater peak hip negative power while encountering the first step. These results identify the importance of the starting position in experiments dealing with biomechanics of stair negotiation. Further, these findings have important implications for studying stair ascent characteristics of other populations such as older adults.

Lower extremity joint kinematics of stair ascent in transfemoral amputees

BACKGROUND

Stair ascent is a very demanding task for transfemoral amputees (TFAs). The purpose of this study was to investigate the lower extremity joint kinematics of TFAs who can climb stairs using a step-over-step gait pattern without an active artificial prosthetic knee joint or handrail use.

CASE DESCRIPTION AND METHODS

Case series. Participants were two traumatic TFAs and 10 control participants. Both TFAs used a single-axis prosthetic knee joint in daily living. Sagittal plane joint kinematics were recorded at 60 Hz using an eight-camera motion analysis system and digital video camera.

FINDINGS AND OUTCOMES

From the instant of touchdown, the prosthetic knee joint was rapidly extended and remained fully extended until toe-off. In the latter half of the stance phase, the knee and ankle joints of the sound limb simultaneously showed rapid joint flexion during continuous extension. Further, the ankle joint of the sound limb showed greater plantarflexion at the end of the stance phase.

CONCLUSION

These results suggest that the TFA in the present study would (1) extend the prosthetic knee joint to prevent the knee flexion generated by the bodyweight (plus ground reaction force and/or joint moment), and (2) lift the whole body in an upward direction using strong counter-movements and greater joint extension during the stance phase.

Kinetic analysis of stair descent: Part 1. Forwards step-over-step descent

This study examined lower extremity biomechanics during the initiation of stair descent from an upright, static posture. Seventeen healthy subjects (aged 23±2.4 years) descended a five-step, steel-reinforced, wooden laboratory staircase (34° decline). Ten trials of stair descent were separated into two blocks of five trials. Beginning from an upright posture, subjects descended the staircase at their preferred velocity (0.53±0.082 m/s) and continued the length of the laboratory walkway (∼4 m). Joint mechanics were contrasted between gait cycles. Relative to the initiation cycle at the top of the staircase, the dissipative knee extensor (K3) and hip flexor (H2) moments and powers were independent of progression velocity and approximated steady-state (i.e., constant) values after the first cycle of the trail limb (Step 5 to Step 3). In contrast, a salient relationship was observed between progression velocity and ankle joint mechanics at initial-contact. The plantiflexor moment, power and work at initial-contact (A1) increased with centre of mass velocity. Our results demonstrate that while the knee extensor moment is the primary dissipater of mechanical energy in stair descent, the ankle plantiflexors are the primary dissipaters associated with increased progression velocity. In addition, the results show that steady-state stair descent may not be attained during the first gait cycle of the trail limb. These data shed light on locomotive strategies used in stair descent and can be applied in biomechanical models of human stair gait. Researchers and practitioners should take into consideration the influence of gait cycle and progression velocity when evaluating lower extremity function in stair descent.

Sagittal and frontal lower limb joint moments during stair ascent and descent in young and older adults

Stair negotiation is an essential skill required for independent mobility, and is described by older adults as a challenging task that is associated with high fall risk. Little is known about the age-related changes in joint kinetics and the relative contribution of lower limb joint moments during stair negotiation. This study characterized lower extremity joint kinetics and their variability associated with stair ascent and descent in young and older adults. Twenty three young and 32 older adults (>55 years) participated. Three dimensional, bilateral gait analysis provided ankle, knee, and hip moment profiles, which in the sagittal plane were summed to provide the support moment. In addition, intra- and inter-subject coefficients of variation were calculated for ensemble averaged curves. Age-related differences were found in the magnitudes of the moment contributions during event transitions for stair ascent and descent. Within groups, the moment profiles were generally consistent. Ankle and knee moments predominantly contributed to extensor support in the sagittal plane. In the frontal plane, proximal joint abductor moments maintained lateral stability and were larger at the hip in older adults. Understanding age-related alterations in movement control during functional tasks can help inform the rehabilitation management and assessment of patient populations.