More than $49.5 billion dollars were spent in 2015 on healthcare due to falls (Florence et al., 2018), and reduced quality of life has been reported years after a fall (Tinetti and Williams, 1998). Together, these data suggest falls are a significant public health concern. A recent population-based cohort study investigating fall risk factors in older adults reported that falls on steps was the third most common fall circumstance (6.8 %) behind walking (50 %) and standing (9.6 %) (Cai et al., 2023). While falls on steps were the third most common fall circumstance, injuries from stairway falls have been shown to result in higher mortality rates than other types of falls (Ragg et al., 2000). Accidents or falls on steps commonly occur during transition step negotiation as the result of foot misplacement (Templer, 1992). Further, as individuals’ age, the likelihood of experiencing a fall increases significantly (Skalska et al., 2013), with those falling more likely to be female (Florence et al., 2018). Additionally, risk for a future fall increases for older adults that have already experienced a fall in the previous year (Carpenter et al., 2009). Age-related changes in lower extremity (hip, knee, ankle) and foot function may be important factors influencing foot placement and landing phase kinematics during transition step negotiation.

Although multi-segment foot models have been used to examine foot function during walking and running gait in young adults (Deschamps et al., 2011), few studies have utilized the models to investigate older adult walking gait (Arnold et al., 2014, Lee et al., 2017, Legault-Moore et al., 2012, van Hoeve et al., 2017) and none have investigated the influence of age on transition step negotiation. Although it has been demonstrated that older adults prefer landing from steps with a plantarflexed ankle (van Dieen and Pijnappels, 2009); given the foot must support almost one-and-a-half times bodyweight during step descent (Hamel et al., 2005), and the foot is composed of 26 bones that form 33 joints, foot function during step descent may be an important factor in step related falls.

To date, only two studies have utilized a multi-segment foot model to investigate step descent kinematics (Gerstle et al., 2017, Rao et al., 2009). Rao et al. (2009) examined foot segment motion between older adults with and without midfoot arthritis both during walking and stepping down a single step. They found differences in mechanics between the groups, which differed by task. During step descent, the arthritis group had greater calcaneus eversion range of motion (ROM). During level walking the only difference was less first metatarsal joint plantarflexion motion in the arthritis group (Rao et al., 2009). Gerstle et al. (2017) investigated differences in foot segment motion across different height steps in young adults. The findings indicated, as step height increased, sagittal plane ROM of the foot increased. While these studies have improved the understanding of foot function during transition step negotiation, a critical gap remains regarding the influence of age and fall history on foot function during step negotiation.

Therefore, the purpose of this study was to identify lower extremity and foot initial contact and landing phase kinematic differences between young women and older women with and without a history of falls during transition or single step descent. At initial contact, due to older adults’ preference to land with a plantarflexed ankle (van Dieen and Pijnappels, 2009) and age-related decreases in lower extremity strength (McKay et al., 2017), the older groups were hypothesized to demonstrate increased foot plantarflexion (rearfoot, medial midfoot, lateral midfoot, medial forefoot, lateral forefoot) and inversion (rearfoot, medial and lateral midfoot) compared to the young group. The increased plantarflexed position may function to allow landing earlier and the more inverted posture may create a more rigid foot to further increase reliance on the bony versus muscular structures (DeVita and Hortobagyi, 2000). Further, the older fall history group was anticipated to land with the foot more plantarflexed and inverted than the older non-fallers. The differences between the older faller and non-faller groups were also anticipated to be due to decreases in lower extremity strength previously reported in older adult fallers versus non-fallers (Robinovitch et al., 2002). With respect to the hip and knee joints at initial contact, we previously reported that older adult fallers and non-fallers landed with the knee significantly more flexed than young adults, but hip position did not differ between the groups (Gerstle et al., 2021).

During the landing phase, the older adult groups were hypothesized to demonstrate smaller ROM in the knee and hip and greater ROM across the foot joints in the sagittal and frontal planes compared to the young group. Between the older groups, those with a fall history were expected to have less ROM at the knee and hip, but greater foot ROM. The hip and knee changes were postulated based on previous results of a walking study by Anderson and Madigan (2014) and a single step study by Saywell et al. (2012). The foot changes were anticipated to be due to the differences in the initial contact positions and age-related decreased strength of the foot and ankle musculature.