Background: Gait abnormalities can influence surgical outcomes in people with severe knee osteoarthritis (OA) and thus a thorough understanding of gait abnormalities in these people prior to arthroplasty is important. Varus-valgus thrust is a characteristic linked to OA disease progression that has not yet been investigated in a cohort with severe knee OA awaiting knee arthroplasty. The aims of this study were to determine i) prevalence of varus and valgus thrust in a cohort with severe knee OA compared to an asymptomatic group, ii) whether the thrust magnitude differed between these groups iii) differences between varus and valgus thrusters within the OA cohort and iv) whether certain measures could predict thrust in the OA cohort.
Methods: 40 patients with severe knee OA scheduled for primary TKR and 40 asymptomatic participants were recruited. Three-dimensional gait analysis was performed on all participants, with the primary biomechanical measures of interest being: varus and valgus thrust, knee adduction angle, peak KAM, and KAM impulse. Additionally, static knee alignment and quadriceps strength were assessed in the subgroup with knee OA.
Findings: No difference was found in the prevalence of varus and valgus thrust between the severe OA and control groups (Pearson chi-square = 3.735, p value = 0.151). The OA varus thrust group had a significantly higher peak KAM (p=0.000), KAM impulse (p=0.001), static alignment (p=0.021), and lower quadriceps strength (p=0.041) than the valgus thrust group. Peak KAM and quadriceps strength were found to explain 34.9% of the variation in maximum thrust, such that an increase in KAM and a decrease in quadriceps strength were associated with an increase in maximum (varus) thrust.
Interpretation: Few differences between the severe OA and control groups were seen, however dichotomizing the groups into varus and valgus cohorts revealed a number of biomechanical differences. Patients with severe OA are often treated as a homogenous cohort; however, by classifying which individuals have a varus or valgus thrust, we have identified a subset of patients with poorer biomechanics who could potentially be at a higher risk of a worse outcome after surgery.
The purpose of this study was to investigate stride rate (SR) dynamics of a recreational runner participating in his debut marathon. Tibial accelerometry data obtained during a half marathon (R1) and marathon (R2) were utilised. SR data were extracted utilising novel computational methods and descriptive statistics were utilised for analysis of R2, and comparison of the first half of the marathon (R2half) to R1. Results indicate that the participant employed comparable SR strategy in R1 and R2half. For R2 a combined decreasing trend in SR and increased variance in SR from 30 km (R2 =0.0238) was observed. Results indicate that the participant had the ability to maintain SR strategy for the first half of the marathon, however as fatigue onset occurred this ability decreased. Running strategies on SR during fatigue may be of future use to recreational runners.
Healthy standing posture is characterized by the ability to interact with a changing environment while maintaining upright stance. Being adaptable to changing environments affords flexibility and allows the system to encounter novel environments without losing control of posture. The purpose of this research was to determine if stroke survivors could adapt to support surface translations with differing temporal structures.
Methods: Eight stroke survivors participated in this research. Participants stood on a force platform on the Neurocom Balance Manager (Neurocom Intl., Clackamas, OR, USA). The support surface was translated in the anteroposterior direction according to waveforms with different temporal structures, this included white noise, pink noise, brown noise, and a sine wave. They also performed a normal standing trial where the platform did not move. Root mean square and detrended fluctuation analysis of the center of pressure signal were calculated to determine amount and temporal structure of variability respectively.
Results: During normal standing the stroke survivors’ posture exhibited lack of adaptability. The stroke survivors had increased amount of variability in all conditions compared to normal standing, regardless of the inherent structure of the support surface translations. The temporal structure of variability indicated weakened long-range correlations in all conditions compared to normal standing. This indicates that regardless of the temporal structure of the support surface movement the amount of movement increased while the structure of movement became more random.
Previous work has demonstrated that healthy posture is able to adapt to the temporal structure of support surface translations, this adaptability was not seen in a population of stroke survivors. This lack of adaptability makes interactions with environmental perturbations difficult and impacts functionality. Focusing rehabilitation protocols towards regaining healthy temporal structures in postural control could improve functionality in chronic stroke survivors.