Impact of Knee Injury and Disease on Frontal Plane Knee Biomechanics During Walk on Uneven Surfaces

Frontal plane knee biomechanics, in particular speed and magnitude of knee adduction motion, are implicated in knee osteoarthritis development. Although individuals are between 50% to 90% more likely to develop knee osteoarthritis after anterior cruciate ligament reconstruction (ACL-R), it is unknown if ACL-R individuals exhibit knee adduction biomechanics related to OA development. This study sought to quantify speed and magnitude of knee adduction for knee OA and ACL-R individuals. We hypothesize that OA will exhibit larger, faster knee adduction biomechanics than ACL-R, which will increase at great walk speed and over a challenging surface. Six individuals with ACL-R and 8 individuals with knee OA had knee adduction quantified as they walked 1.3 m/s and at a self-selected speed over a flat and an uneven surface. Peak of stance, and average and maximum velocity of knee adduction joint angle and moment between heel strike and peak of stance were submitted to repeated measures ANOVA to compare main and interaction effects between group, speed and surface. There was a walk speed by group interaction for peak knee adduction moment (p = 0.048). Walk speed impacted maximum knee adduction joint angle (p=0.004) and moment velocity (p=0.041), while surface impacted peak knee adduction joint angle (p=0.035) and maximum knee adduction joint moment velocity (p=0.007). In partial agreement with our hypothesis, speed and magnitude knee adduction biomechanics increased with walk speed and surface, but OA did not consistently exhibit larger knee adduction biomechanics than ACL-R

Age Impacts Lower Limb Stiffness During Distracted Negotiation of Slick Stairs

Older adults (OA, over 65 years) typically use compensatory gait strategies for safe stair descent. Adequate lower limb stiffness, including leg and individual joint (i.e., hip, knee, and ankle), may be necessary to prevent falling, particularly when negotiating a slick surface or when the individual is distracted. Yet, it is unknown if OA change lower limb stiffness for safe stair descent during these challenging situations. Thus, 13 young adults (YA, between 18-25 years) and 12 OA had leg and lower limb joint stiffness quantified during a stair descent (18.5 cm rise). Each participant performed the stair descent on normal and slick surfaces, and with and without cognitive distraction. Leg stiffness (quantified as change in leg length when ground reaction force is applied) and hip, knee and ankle joint stiffness (calculated as change in joint angle when a joint moment is applied) were submitted to 3-way mixed model ANOVA. 3-way interaction for ankle stiffness (p = 0.036) was observed. Without a distraction, the YA exhibited a stiffer ankle on the normal compared to slick surface (p = 0.007), but YA did not change ankle stiffness when distracted (p = 0.125). Neither distraction, nor surface impacted OA ankle stiffness (p \u3e 0.05). YA exhibited a stiffer hip than OA (p = 0.009), and all participants increased hip stiffness on the slick surface (p = .001). Leg and knee stiffness did not differ by age, or change with surface or distraction (p \u3e 0.05). YA may possess the neuromuscular function to increase hip and ankle stiffness during stair descent. Future work is needed to determine whether OA changes in lower limb stiffness are an attempt to prevent accidental fall or from compromised muscular function

Surface, but Not Age Impacts Lower Limb Joint Work During Stair Ascent

Introduction: Age-related loss in lower limb strength, particularly at the ankle, may impair older adults (over 65 years of age) mobility, and result in biomechanical deficits compared to their younger counterparts. Older adults tend to walk slower with shorter steps and exhibit diminished ankle joint kinetics (i.e., moment, power and work) while walking and stepping up. Although the compromised ankle function leads older adults to produce smaller ankle joint torques and power output, reducing forces to propel the center of mass forward, it is unclear if they redistributed, or increase hip or knee work to safely walk, particularly when challenged with an uneven or slick surface. Objective: To compare positive lower limb work for young and older adults when walking over and stepping up with challenging surfaces, and determine whether redistributed power output. Methods: Twenty-eight (16 young, 18 to 25 years and 12 older, over 65 years) adults had positive work in the lower limb quantified when walking and stepping up at a self-selected speed over three surfaces (normal, uneven, and slick). Total limb, hip, knee and ankle positive work, and relative effort (% of total) at each joint were submitted to RM ANOVA to test main effect and interaction between surface (normal, uneven, and slick) and age (young and older adults). Results: Surface, but not age impact positive lower limb work. Surface impacted total limb (p=0.000), hip (p=0.007) and knee (p=0.001) positive work. The limb and knee produced more positive work on the uneven compared normal (