Mechanical energy transfers across lower limb segments during stair ascent and descent in young and healthy older adults

Older adults present with altered movement patterns during stair negotiation although the extent to which modifications in pattern and speed influence mechanical efficiency is unknown. This study evaluated mechanical energy transfers attributed to active force production during stair negotiation in young and older adults to provide insight into age-related changes in mechanical efficiency. Secondary analysis on data obtained from 23 young (23.7 ± 3.0 years) and 32 older adults (67.0 ± 8.2 years) during self-paced stair ascent and descent was conducted. Mechanical energy expenditures (MEE) during concentric transfer, eccentric transfer and no-transfer phases were determined for the ankle, knee and hip power profiles in the sagittal plane. Mechanical energy compensations (MEC) were also determined at each joint. During ascent, MEEs were similar for young and older adults although older adults compensated ankle muscles to a lesser extent during concentric muscle action. Controlling for cadence eliminated this difference. During descent, older adults demonstrated lower energy expenditures at the ankle and hip and similar expenditures at the knee compared to young adults. Changes in joint MEE in the older group resulted in reduced energy compensation at the ankle during concentric and eccentric activity and at the knee during eccentric activity. These age-related differences in mechanical energy transfers and related adjustments in MEC were not a function of the slower cadence in older adults and suggest a loss in mechanical efficiency. These results provide a benchmark against which physical impairments in older adults may be explored.     

Influence of light handrail use on the biomechanics of stair negotiation in old age

The high incidence of falls in older adults during stair negotiation suggests that this task is physically challenging and potentially dangerous. The present study aimed to examine the influence of light handrail use on the biomechanics of stair negotiation in old age. Thirteen older adults ascended and descended a purpose-built staircase at their self-selected speed: (i) unaided and (ii) with light use of the handrails. Ground reaction forces (GRFs) were measured from force platforms mounted into each step and motion capture was used to collect kinematic data. Knee and ankle joint moments were calculated using the kinetic and kinematic data. The horizontal separation between the centre of mass (COM) and the centre of pressure (COP) was assessed in the sagittal and frontal planes. During stair ascent, handrail use caused a different strategy to be employed compared to unaided ascent with a redistribution of joint moments. Specifically, the ankle joint moment (of the trailing leg) was reduced with handrail use, which has previously been shown to approach its limits during unaided stair ascent, but the knee joint moment (of the leading leg) increased. Previous research has shown that a larger joint moment reserve is available at the knee during unaided stair ascent. During stair descent, the ankle joint moment increased with handrail use, this was associated, however, with a more effective control of balance as shown by a reduced COM-COP separation in the direction of progression compared to unaided descent. These results indicate that although the biomechanical mechanisms are different for stair ascent and descent, the safety of stair negotiation is improved for older adults with light use of the handrails.     

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.     

Evidence of compensatory joint kinetics during stair ascent and descent in Parkinson’s disease

BackgroundStair ambulation is a challenging activity of daily life that requires larger joint moments than walking. Stabilisation of the body and prevention of lower limb collapse during this task depends upon adequately-sized hip, knee and ankle extensor moments. However, people with Parkinson’s disease (PD) often present with strength deficits that may impair their capacity to control the lower limbs and ultimately increase their falls risk.ObjectiveTo investigate hip, knee and ankle joint moments during stair ascent and descent and determine the contribution of these joints to the body’s support in people with PD.MethodsTwelve PD patients and twelve age-matched controls performed stair ascent and descent trials. Data from an instrumented staircase and a three-dimensional motion analysis system were used to derive sagittal hip, knee and ankle moments. Support moment impulses were calculated by summing all extensor moment impulses and the relative contribution of each joint was calculated.ResultsLinear mixed model analyses indicated that PD patients walked slower and had a reduced cadence relative to controls. Although support moment impulses were typically not different between groups during stair ascent or descent, a reduced contribution by the ankle joint required an increased knee joint contribution for the PD patients.ConclusionsDespite having poorer knee extensor strength, people with PD rely more heavily on these muscles during stair walking. This adaptation could possibly be driven by the somewhat restricted mobility of this joint, which may provide these individuals with an increased sense of stability during these tasks.     

The biomechanical functional demand placed on knee and hip muscles of older adults during stair ascent and descent

Age-related decline in physical capabilities may lead to older adults experiencing difficulty in performing everyday activities due to high demands placed on the muscles of their lower extremity. This study aimed to determine the biomechanical functional demand in terms of joint moments and maximal muscle capabilities at the knee and hip joints while older adults performed stair ascent (SA) and stair descent (SD). Eighty-four healthy older adults aged 60-88 years were tested. A torque dynamometer attached to a purpose-built plinth was utilized to measure muscle moments at the knee and hip joints. Participants also underwent full body 3-D biomechanical assessment of stair ascent and descent using an 8-camera VICON system (120 Hz) with 3 Kistler force plates. Stair negotiation required knee extensor moments in excess of the maximum isometric muscle strength available (SA 103%, SD 120%). For the hip, the levels of demand were high, but were slightly lower than those of the knee joint. Stair negotiation placed a high level of demand on the knee extensors with demand in SA reaching maximal isometric capacity and demand in SD exceeding maximal isometric capacity. The levels of demand leave little reserve capacity for the older adult to draw on in unexpected situations or circumstances.     

Influence of the exacerbation of patellofemoral pain on trunk kinematics and lower limb mechanics during stair negotiation

BackgroundAlthough it is assumed that the presence of patellofemoral pain (PFP) may result in compensatory behaviors that can alter trunk kinematics and lower limb mechanics, the influence of the exacerbation of patellofemoral pain on trunk kinematics and lower limb mechanics during stair negotiation has not been established.Research questionDoes the exacerbation of PFP symptoms lead to altered trunk kinematics and lower limb mechanics during stair negotiation?MethodsThree-dimensional kinematics and kinetics were obtained from 45 women with PFP during stair descent and ascent. Data were obtained before and after a pain exacerbation protocol. The variables of interest were peak trunk, hip, and knee flexion, and ankle dorsiflexion; peak hip, and knee extensor, and ankle plantarflexor moments. Paired t-tests were used to compare the variables of interest before and after pain exacerbation.ResultsFollowing pain exacerbation, there was a decrease in peak knee extensor moment during stair descent (Effect size = −0.68; p = 0.01) and stair ascent (Effect size = −0.56; p = 0.02); as well as in peak ankle dorsiflexion during stair descent (Effect size = −0.33; p = 0.01) and stair ascent (Effect size = −0.30; p = 0.01). An increase in ankle plantarflexor moment during stair descent (Effect size = 0.79; p < 0.01) and stair ascent (Effect size = 0.89; p < 0.01) was also observed. No significant differences were observed for peak trunk, hip, and knee flexion or hip extensor moment (p > 0.05).SignificanceOur findings show compensatory strategies used by people with PFP in response to symptoms exacerbation that may have a negative impact on knee and ankle mechanics. Our findings also suggest that people with PFP do not seem to change their trunk, hip, and knee flexion or hip extensor moment during stair negotiation in response to symptom exacerbation.     

Age-related joint moment characteristics during normal gait and successful reactive-recovery from unexpected slip perturbations

The objective of the current study was to investigate the effects of aging on 3D lower extremity joint moments during successful reactive-recovery from unexpected slips. Unexpected slips were induced by having participants walk over a slippery floor surface. Successful reactive-recovery trials from nine young and nine elderly participants were identified and analyzed. Three-dimensional inverse dynamics were implemented to calculate reactive joint moments at the ankle, knee, and hip joints. Peak joint moment magnitude and the speed of peak joint moment generation were used to describe the balance recovery strategies from unexpected slips. Results indicated significantly higher peak joint moments in recovery than in normal walking for both the young and elderly. Meanwhile, during reactive-recovery, the elderly were found to utilize both frontal and sagittal joint moments while the younger adults relied primarily on sagittal joint moment. It was concluded that the ankle and knee joints were critical in controlling sagittal plane motion disturbance, while the hip joint was mainly responsible for stabilizing upper body balance in the frontal plane. This study confirmed age-related differences in joint moment generation during unexpected slips. Additionally, implementing 3D analysis is recommended in future slips and falls research.     

Kinetic analysis of forwards and backwards stair descent

The activity of descending stairs increases loading at the joints of the lower extremities as compared to walking, which may cause discomfort and or difficulties in completing the task. This study compared and contrasted the kinematics and kinetics of both forwards and backwards stair descent to those of level walking. We compared the support moments and moment powers of the lower limb joints while descending stairs forwards at a self-selected pace, backwards at a self-selected pace and forwards at the same pace as backwards. Participants were 10 healthy young adults (6 men and 4 women) aged 20–35 years. Sagittal plane kinematics and ground reaction forces were collected and moments of force computed using inverse dynamics. The ratio of stance/swing phase changed from 59:41 for normal level walking to between 65:35 and 70:30 for forward stair descent but backwards descent was 58:42. Stair descent produced larger double-peak support moments with reduced ankle plantar flexor and increased knee extensor moments as compared to level walking (>±95th-percentile confidence interval). The hip moments during stair descent were relatively small and highly variable. We observed significantly larger distances between the centres of pressure and the stair edges for backwards stair descent versus forwards stair descent. These results demonstrate that stair descent, even at a slower pace, requires greater power from the knee extensors than level walking but that backwards stair descent significantly reduced the peak knee power during midstance and provided a potentially safer means of descending stairs than forwards stair descent.     

Knee and hip kinetics during normal stair climbing

Understanding joint kinetics during activities of daily living furthers our understanding of the factors involved in joint pathology and the effects of treatment. In this study, we examined hip and knee joint kinetics during stair climbing in 35 young healthy subjects using a subject-specific knee model to estimate bone-on-bone tibiofemoral and patello-femoral joint contact forces. The net knee forces were below one body weight while the peak posterior-anterior contact force was close to one body weight. The peak distal-proximal contact force was on average 3 times body weight and could be as high as 6 times body weight. These contact forces occurred at a high degree of knee flexion where there is a smaller joint contact area resulting in high contact stresses. The peak knee adduction moment was 0.42 (0.15) Nm/kg while the flexion moment was 1.16 (0.24) Nm/kg. Similar peak moment values, but different curve profiles, were found for the hip. The hip and knee posterior-anterior shear forces and the knee flexion moment were higher during stair climbing than during level walking. The most striking difference between stair ascent and level walking was that the peak patello-femoral contact force was 8 times higher during stair ascent. These data can be used as baseline measures in pathology studies, as input to theoretical joint models, and as input to mechanical joint simulators.     

Kinematics of stair descent in young and older adults and the impact of exercise training

Stair descent is a challenging task in old age. This study firstly investigated lower extremity kinematics during stair descent in young (YOU) and healthy, community dwelling older adults (OLD). Secondly, the impact of an exercise training intervention on age-related differences in stair descent was assessed. At baseline, a motion analysis system was used to determine spatio-temporal gait variables and lower extremity kinematics as YOU (n=23, age=27+/-3 years) and OLD (n=34, age=73+/-4 years) descended a three step staircase. The older adults were then divided into training (TRA) and control (CON) groups. For 12 months, TRA performed resistance, aerobic, balance, and flexibility exercises under supervision in a class environment (twice per week) and unsupervised at home (once per week). CON carried on with normal daily activities. Following the intervention, baseline measurements were repeated in TRA and CON. At baseline, total descent, stride cycle, and single support times were longer in OLD than in YOU. In addition, sagittal plane knee motion was lower in OLD whilst frontal and transverse plane pelvis and hip motion were higher in OLD. Exercise training did not reduce the age-related differences observed. In conclusion healthy older adults perform stair descent at a slower speed and with greater motion outside the plane of progression than young adults. We found no evidence that these differences are reduced by generic exercise training, at least in non-frail older adults.     

The kinematic and kinetic effects of solid, hinged, and no ankle-foot orthoses on stair locomotion in healthy adults

This study compared the effects of a unilateral solid ankle-foot orthosis (AFO), hinged AFO and no AFO (shoe) worn by healthy adults on pelvic angles, lower extremity joint angles, moments and powers, and temporal-spatial gait characteristics during stair locomotion. A convenience sample of 19 healthy adults participated in this repeated measures design with subjects serving as their own controls. Subjects ambulated on stairs wearing a left shoe and either a right solid AFO, hinged AFO or shoe. Kinematic and kinetic data were collected with motion analysis equipment and a force plate for the three conditions. Pelvic angles and right hip, knee and ankle angles, moments and powers during stance were compared to determine differences among the conditions. Subjects wearing either orthosis walked slower during stair locomotion and with a shorter right single limb support time during descent. Sagittal knee and ankle angles, moments and powers were similar in individuals wearing a hinged AFO or shoe during pull-up (PU) in ascent and controlled lowering (CL) in descent. Decreased ankle dorsiflexion angle, plantar flexion power, knee flexion angle and extensor moment were seen in subjects wearing a solid AFO as compared to a hinged AFO during PU in ascent and CL in descent. Findings contributed to understanding how biomechanical changes imposed at the ankle by a unilateral solid AFO resulted in more kinetic and kinematic compensations than the hinged AFO in healthy adults without the confounding effects of neuromuscular impairments.     

Centre of mass control is reduced in older people when descending stairs at an increased riser height

BackgroundMaintaining body centre of mass (CoM) lowering velocity within manageable/safe limits during stair descent can be problematic for older individuals due to reduced ranges of motion at the involved joints (ankle and knee) and a reduced ability to generate adequate joint moments at the extremes in joint ranges of motion. These problems are likely to magnify in circumstances where the distance of lowering increases, or when misjudging the height of lowering.Research questionHow does a 50% increase in standard stair riser-height affect control of CoM velocity and acceleration of older people during stair descent?MethodsFifteen older (75 ± 3 years) and seventeen young (25 ± 4 years) healthy adults descended a 4-step staircase, at two riser-heights: 170 mm, 255 mm. Changes in peak vertical CoM acceleration and velocity, and lower-limb joint kinetics (moments, work) during landing and lowering phases of stair descent were assessed using a mixed-design repeated measures analysis of variance.ResultsPeak CoM accelerations and velocities during landing and lowering were lower in older compared to young adults and increased in both groups at 255 mm riser-height. Duration of lowering also increased, particularly for older adults. Peak ankle moments during landing and lowering, which were lower in older compared to young adults, increased when descending from 255 mm riser-height, whilst the peak knee moment reduced. Both groups produced increased landing-limb negative (eccentric) ankle joint work when descending from 255 mm, but increases were greater for older adults (87.8%) compared to young (76.1%).SignificanceDescending stairs became more challenging in both age groups as riser-height increased. Older adults adopted a strategy of reducing CoM velocity to lessen the eccentric landing demands. In both groups, but more so older adults, there was a greater reliance on using leading-limb eccentric plantarflexion at 255 mm riser-height compared to 170 mm, to arrest/control increased downward CoM velocity and acceleration during landing.     

Carrying asymmetric loads during stair negotiation

Individuals often carry items in one hand instead of both hands during activities of daily living. The combined effects of carrying asymmetric loads and stair negotiation may create even higher demands on the low back and lower extremity. The purpose of this study was to investigate the effect of symmetric and asymmetric loading conditions on L5/S1 and lower extremity moments during stair negotiation. Twenty-two college students performed stair ascent and stair descent on a three-step staircase (step height 18.5 cm, tread depth 29.5 cm) at preferred pace under five load conditions: no load, 10% body weight (BW) unilateral load, 20% BW unilateral load, 10% BW bilateral load, and 20% BW bilateral load. Video cameras and force platforms were used to collect kinematic and kinetic data. Inverse dynamics was used to calculate frontal plane moments for the L5/S1 and lower extremity. A 20% BW unilateral load resulted in significantly higher peak L5/S1 lateral bending, hip abduction, and external knee varus moments than nearly all other loading conditions during stair ascent and stair descent. Therefore, we suggest potential benefits when carrying symmetrical loads as compared to an asymmetric load in order to decrease the frontal joint moments, particularly at 20% BW load.     

Knee adduction moments are not increased in obese knee osteoarthritis patients during stair negotiation

BackgroundNegotiating stairs is an important activity of daily living that is also associated with large loads on the knee joint. In medial compartment knee osteoarthritis, the knee adduction moment during level walking is considered a marker for disease severity. It could be argued that the discriminative capability of this parameter is even better if tested in a strenuous stair negotiation task.Research questionWhat is the relation with knee osteoarthritis on the knee adduction moment during the stance phase of both stair ascent and descent in patients with and without obesity?MethodsThis case control study included 22 lean controls, 16 lean knee osteoarthritis patients, and 14 obese knee osteoarthritis patients. All subjects ascended and descended a two-step staircase at a self-selected, comfortable speed. Three-dimensional motion analysis was performed to evaluate the knee adduction moment during stair negotiation.ResultsObese knee osteoarthritis patients show a prolonged stance time together with a more flattened knee adduction moment curve during stair ascent. Normalized knee adduction moment impulse, as well as the first and second peaks were not different between groups. During stair descent, a similar increase in stance time was found for both osteoarthritis groups.SignificanceThe absence of a significant effect of groups on the normalized knee adduction moment during stair negotiation may be explained by a lower ambulatory speed in the obese knee osteoarthritis group, that effectively lowers vertical ground reaction force. Decreasing ambulatory speed may be an effective strategy to lower knee adduction moment during stair negotiation.     

Altered joint moment strategy during stair walking in diabetes patients with and without peripheral neuropathy

AimTo investigate lower limb biomechanical strategy during stair walking in patients with diabetes and patients with diabetic peripheral neuropathy, a population known to exhibit lower limb muscular weakness.MethodsThe peak lower limb joint moments of twenty-two patients with diabetic peripheral neuropathy and thirty-nine patients with diabetes and no neuropathy were compared during ascent and descent of a staircase to thirty-two healthy controls. Fifty-nine of the ninety-four participants also performed assessment of their maximum isokinetic ankle and knee joint moment (muscle strength) to assess the level of peak joint moments during the stair task relative to their maximal joint moment-generating capabilities (operating strengths).ResultsBoth patient groups ascended and descended stairs slower than controls (p < 0.05). Peak joint moments in patients with diabetic peripheral neuropathy were lower (p < 0.05) at the ankle and knee during stair ascent, and knee only during stair descent compared to controls. Ankle and knee muscle strength values were lower (p < 0.05) in patients with diabetic peripheral neuropathy compared to controls, and lower at knee only in patients without neuropathy. Operating strengths were higher (p < 0.05) at the ankle and knee in patients with neuropathy during stair descent compared to the controls, but not during stair ascent.ConclusionPatients with diabetic peripheral neuropathy walk slower to alter gait strategy during stair walking and account for lower-limb muscular weakness, but still exhibit heightened operating strengths during stair descent, which may impact upon fatigue and the ability to recover a safe stance following postural instability.     

Kinematics and kinetics with an adaptive ankle foot system during stair ambulation of transtibial amputees

Conventional prosthetic feet cannot adapt to specific conditions such as walking on stairs or ramps. Amputees are therefore forced to compensate their prosthetic deficits by modifying the kinematics and kinetics of their lower limbs. The Proprio-Foot™ (Ossur) intends to reduce these compensation mechanisms by automatically increasing dorsiflexion during stair ambulation thanks to an adaptive microprocessor-controlled ankle. The present investigation proposes to analyze the biomechanical effects of the dorsiflexion adaptation in transtibial (TT) amputees during stair ambulation.Sixteen TT amputees and sixteen healthy controls underwent conventional 3D gait analysis. Kinematics and kinetics of the lower limbs were compared during stair ascent and descent performed by patients with the prosthetic foot set to a neutral ankle angle and with an adapted dorsiflexion ankle angle of 4°. Norm distance as well as minimum and maximal values of sagittal kinematics and kinetics were calculated for comparisons between patients and control subjects.For both stair ascent and descent, an improvement of the knee kinematics and kinetics could particularly be noticed on the involved side with an increase of the knee flexion and an increase of the knee moment during stance.Therefore, despite its additional weight compared to a conventional prosthetic ankle, the Proprio-Foot™ should be beneficial to active TT amputees whose knee musculature strength does not constitute a handicap.     

Lower extremity kinematics and kinetics during level walking and stair climbing in subjects with triple arthrodesis or subtalar fusion

The purpose of this study was to identify the kinematic and kinetic strategies used by patients with unilateral triple arthrodesis or subtalar fusion during level walking, stair ascent, stair descent and to determine the influence of these different conditions on kinematics and kinetics. Nine subjects with unilateral triple or subtalar fusion and five normal control subjects were recruited for this experiment. Temporal distance, kinematic and kinetic data were collected using a six camera 3-D motion analysis system and a custom fabricated set of stairs with five steps; the second and third steps were each instrumented with one force platform. During level walking, affected limbs lost all of the plantarflexion at the ankle joint during push-off and showed greater knee flexion angle during the same period of stance. During stair ascent, affected limbs showed a different movement pattern at the knee, a greater knee flexion angle during the whole stance phase and a near zero degree of plantarflexion angle during the forward continuance (FCN) phase. During descent, affected limbs showed a greater knee flexion angle during the whole stance phase and less ankle dorsiflexion angle during the same period of stance phase. At the ankle, peak moment and power values were significantly different between the affected side and the limbs of the control subjects during level walking in the push-off phase, stair ascent in the FCN phase, and stair descent in the weight acceptance (WA) phase, where the affected limbs had a lower plantarflexion moment and power values.     

Six degree of freedom joint power in stair climbing

In the past, joint power has most often been calculated as the product of the sagittal plane joint moment and the sagittal plane joint angular velocity, thus modelling the joint as a simple one degree of freedom (DOF) hinge. More recently three DOF power has been calculated by taking the scalar product of the net joint moment and the angular velocity of the joint, thus modelling the joint as a ball and socket joint. We introduce a six DOF approach for calculating joint power, an approach which allows three degrees of rotational freedom, as well as three degrees of translational freedom, thus implementing a rigorous definition of true mechanical power. We established that for the hip joint during stair ascent, three DOF power was significantly greater than six DOF power (by as much as 60 W/kg), while for stair descent, one DOF power was significantly less than six DOF power (by up to 45 W/kg). On the basis of the total work done in raising the body up a set of stairs (weight × height), the six DOF approach provided more accurate results than either the one or three DOF models. We also showed that six DOF power data were as repeatable as joint moments, with variance ratios between 0.13 and 0.20. While these findings are certainly not the definitive word, they do offer some guidance regarding the effect that certain assumptions have when calculating joint power in three dimensions.     

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.

Level of evidence

Case–control study, Level III.     

Knee biomechanics of alternate stair ambulation patterns

PURPOSE: This study compared the kinematics and kinetics of the knee joint during traditional step-over-step (SOS) and compensatory step-by-step lead-leg (SBSL) and trail-leg (SBST) stair ambulation patterns. METHODS: Seventeen (M:9) healthy adults completed five trials of ascent and descent using three different stepping patterns: 1) SBSL, 2) SBST, and 3) SOS. Kinematics and kinetics were collected with an optoelectronic motion-tracking system and a force plate embedded into a four-step staircase. An inverse-dynamics link-segment model (QGAIT system) was used to calculate the net joint kinetics. RESULTS: During stair ascent, different peak anteroposterior (AP) forces were observed across all three stepping patterns (SOS > SBSL > SBST, P < 0.05). During ascent, the flexion moments of SOS (0.96 N x m x kg(-1)) and SBSL (0.97 N x m x kg(-1)) patterns were similar and much larger than the SBST moments (0.14 N x m x kg(-1)). In the descent conditions, the initial AP peak force for SOS was larger than that of SBSL and SBST. However, the second peak force for SOS (4.92 N x kg(-1)) and SBST (4.68 N x kg(-1)) were larger than SBSL (1.57 N x kg(-1)). During descent, the initial peak flexion moment for the SOS pattern was larger than SBSL and SBST, whereas during the second peak, SOS (1.05 N x m x kg(-1)) and SBST (1.11 N x m x kg(-)) were no different and larger than SBSL (0.18 N x m x kg(-1)). CONCLUSION: Overall, SBSL during ascent and SBST during descent had the highest loads. These results increase our understanding of alternative stepping patterns and have important clinical (reduction of loading on injured/diseased leg) and rehabilitation implications.