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.

The influence of gait pattern on signs of knee osteoarthritis in older adults over a 5-11 year follow-up period: a case study analysis.

There is evidence that joint load is a factor in the development of osteoarthritis (OA) and, while altered gait profiles have been linked with OA, it is unknown if abnormal gait is a cause or effect of the disease. While the knee's adduction moment has been implicated in the development and progression of knee OA, it is also known that shearing forces are detrimental to the health of cartilage. The purpose of this pilot study was to examine the adduction moment and gait shear forces to determine if they may lead to signs of knee OA in older adults as they age. Knee gait kinetics, standardized radiographs and a questionnaire were collected on 28 older adults (M:13) during an initial visit, and 5 to 11 years later. Radiographic score increased (knees became more osteoarthritic in 15 of 28 subjects) over time. However, gait time-distance measures remained constant in disease free participants. Two returning participants developed symptoms and radiographic evidence of knee OA. The subject with the largest adduction moment developed signs of medial OA while the subject with the smallest adduction moment developed signs of lateral OA. In addition, there was a strong correlation between the magnitudes of the adduction moment and lateral-medial shear force that needs to be investigated further. Results suggest that gait can remain stable over time in older adults. Also, the medial and lateral OA case study findings suggest that the extreme gait profiles seen in these two participants may be important in explaining cartilage breakdown and the development of OA. This longitudinal study would suggest that perhaps it is the abnormal gait pattern that leads to the development of OA, although a much larger study would be needed to confirm this finding.

Relationship between stair ambulation with and without a handrail and centre of pressure velocities during stair ascent and descent.

INTRODUCTION: Stair ambulation is one of the most challenging and hazardous types of locomotion for older adults and often requires the adoption of compensatory strategies such as increased handrail use to mitigate disability and increase stability. Centre of pressure velocity (VCOP) describes the neuromuscular response to shifts of the body's centre of mass and serves as an indicator of stability. Knowledge of VCOP may provide some understanding of strategies to improve measured and perceived stability during stair negotiation. The aim of this study was to compare VCOP during stair ascent and descent with and without a handrail in young, older and older adults with a fear of falling (FOF) populations. METHODS: COP velocities of 23 young adults (23.7±3.0 yrs), 26 older adults (66.4±8.3 yrs), and 3 older adults with FOF (80.2±8.0 yrs) were analyzed while they ascended and descended a custom 4-step staircase. VCOP were obtained using a force plate mounted on concrete blocks centered on the second step of the staircase. RESULTS: During stair ascent and descent with and without a handrail, the VCOP between young and older adults were comparable. The three adults with FOF demonstrated reduced VCOP during ascent and descent without the handrail and even slower VCOP when ascending and descending stairs with the handrail. These results suggest that handrail use does not increase biomechanical stability for healthy, older adults. However, in the presence of fear of falling the use of the handrail enhances dynamic stability, particularly during stair descent. CONCLUSIONS: This study provides the first detailed description of dynamic stability during stair ambulation with and without a handrail. Observations from those with FOF aid in understanding the nature of compensations to improve actual and perceived stability.

Differentiation of young and older adult stair climbing gait using principal component analysis.

INTRODUCTION: Principal component analysis (PCA) has been used to reduce the volume of gait data and can also be used to identify the differences between populations. This approach has not been used on stair climbing gait data. Our objective was to use PCA to compare the gait patterns between young and older adults during stair climbing. METHODS: The knee joint mechanics of 30 healthy young adults (23.9 + or - 2.6 years) and 32 healthy older adults (65.5 + or - 5.2 years) were analyzed while they ascended a custom 4-step staircase. The three-dimensional net knee joint forces, moments, and angles were calculated using typical inverse dynamics. PCA models were created for the knee joint forces, moments and angles about the three axes. The principal component scores (PC scores) generated from the model were analyzed for group differences using independent samples t-tests. A stepwise discriminant procedure determined which principal components (PCs) were most successful in differentiating the two groups. RESULTS: The number of PCs retained for analysis was chosen using a 90% trace criterion. Of the scores generated from the PCA models nine were statistically different (p < .0019) between the two groups, four of the nine PC scores could be used to correctly classify 95% of the original group. CONCLUSIONS: The PCA and discriminant function analysis applied in this investigation identified gait pattern differences between young and older adults. Identification of stair gait pattern differences between young and older adults could help in understanding age-related changes associated with the performance of the locomotor task of stair climbing.