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Multiple sclerosis is a neurodegenerative disease that causes balance deficits, even in early stages. Evidence suggests that people with multiple sclerosis (PwMS) rely more on vision to maintain balance, and challenging balance with optical flow perturbations may be a practical screening for balance deficits. Whether these perturbations affect standing balance in PwMS is unknown. Therefore, the purpose of this study was to examine how optical flow perturbations affect standing balance in PwMS. We hypothesized that perturbations would cause higher variability in PwMS compared with matched controls during standing and that standing balance would be more susceptible to anterior–posterior (A–P) perturbations than medial–lateral (M–L) perturbations. Thirteen PwMS and 13 controls stood under 3 conditions: unperturbed, M–L perturbation, and A–P perturbations. A–P perturbations caused significantly higher A–P trunk sway variability in PwMS than controls, although both groups had similar center-of-pressure variability. Both perturbations increased variability in A–P trunk sway and center of pressure. Trunk variability data supported the hypothesis that PwMS were more susceptible to optical flow perturbations than controls. However, the hypothesis that A–P perturbations would affect balance more than M–L perturbations was partially supported. These results suggest potential for optical flow perturbations to identify balance deficits in PwMS. [ABSTRACT FROM AUTHOR]

Lesser peak vertical ground reaction force (vGRF) has been widely reported among individuals with anterior cruciate ligament reconstruction (ACLR). Peak vGRF remains less than uninjured controls and relatively stable during the first year following ACLR. However, it is unknown whether there are subgroups of individuals exhibiting consistently greater peak vGRF in the first 6‐months following ACLR and if individuals with consistently greater peak vGRF exhibit kinematic and kinetic gait differences compared to individuals with low vGRF. The purpose of this study was to determine if distinct clusters exist based upon magnitude of peak vGRF 2‐ and 6‐months post‐ACLR. Subsequently, we explored between cluster differences in vGRF, knee flexion angle, and sagittal and frontal plane knee kinetics throughout stance between clusters. Forty‐three individuals (58.1%female, 21.4 ± 4.4 years‐old, 95.3% patellar‐tendon autograft) completed five gait trials at their habitual walking speed 2‐ and 6‐months post‐ACLR. A single K‐means cluster analysis was used to identify clusters of individuals based on peak vGRF at 2‐ and 6‐months post‐ACLR. Functional waveform analyses were used to compare gait outcomes between clusters with and without controlling for gait speed and age. We identified two clusters that included a subgroup with high vGRF (n = 16) and low vGRF (n = 27). The cluster with high vGRF demonstrated greater vGRFs, knee flexion angles, and knee extension moments during early stance as compared to the low vGRF cluster 2‐ and 6‐months post‐ACLR. Individuals with peak vGRF ≥1.02 times body‐weight 2‐months post‐ACLR had 35.4 times greater odds of being assigned to the high vGRF cluster. [ABSTRACT FROM AUTHOR]

Insufficient quadriceps force production and altered knee joint biomechanics after anterior cruciate ligament reconstruction (ACLR) may contribute to a heightened risk of osteoarthritis. Quadriceps muscle lengthening dynamics affect force production and knee joint loading; however, no study to our knowledge has quantified in vivo quadriceps dynamics during walking in individuals with ACLR or examined correlations with joint biomechanics. Our purpose was to quantify bilateral vastus lateralis (VL) fascicle length change and the association thereof with gait biomechanics during weight acceptance in individuals with ACLR. The authors hypothesized that ACLR limbs would exhibit more fascicle lengthening than contralateral limbs. The authors also hypothesized that ACLR limbs would exhibit positive correlations between VL fascicle lengthening and knee joint biomechanics during weight acceptance in walking. The authors quantified VL contractile dynamics via cine B-mode ultrasound imaging in 18 individuals with ACLR walking on an instrumented treadmill. In partial support of our hypothesis, ACLR limb VL fascicles activated without length change on average during weight acceptance while fascicle length on the contralateral limb decreased on average. The authors found a positive association between fascicle lengthening and increase in knee extensor moments in both limbs. Our results suggest that examining quadriceps muscle dynamics may elucidate underlying mechanisms relevant to osteoarthritis. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study was to compare the vertical (vGRF), anterior‐posterior (apGRF), and medial‐lateral (mlGRF) ground reaction force (GRF) profiles throughout the stance phase of gait (1) between individuals 6 to 12 months post–anterior cruciate ligament reconstruction (ACLR) and uninjured matched controls and (2) between ACLR and individuals with differing radiographic severities of knee osteoarthritis (KOA), defined as Kellgren and Lawrence (KL) grades KL2, KL3, and KL4. Methods: A total of 196 participants were included in this retrospective cross‐sectional analysis. Gait biomechanics were collected from individuals 6 to 12 months post‐ACLR (n = 36), uninjured controls matched to the ACLR group (n = 36), and individuals with KL2 (n = 31), KL3 (n = 67), and KL4 osteoarthritis (OA) (n = 26). Between‐group differences in vGRF, apGRF, and mlGRF were assessed in reference to the ACLR group throughout each percentage of stance phase using a functional linear model. Results: The ACLR group demonstrated lower vGRF and apGRF in early and late stance compared to the uninjured controls, with large effects (Cohen's d range: 1.35–1.66). Conversely, the ACLR group exhibited greater vGRF (87%–90%; 4.88% body weight [BW]; d = 0.75) and apGRF (84%–94%; 2.41% BW; d = 0.79) than the KL2 group in a small portion of late stance. No differences in mlGRF profiles were observed between the ACLR and either the uninjured controls or the KL2 group. The magnitude of difference in GRF profiles between the ACLR and OA groups increased with OA disease severity. Conclusion: Individuals 6 to 12 months post‐ACLR exhibit strikingly similar GRF profiles as individuals with KL2 KOA, suggesting both patient groups may benefit from targeted interventions to address aberrant GRF profiles. [ABSTRACT FROM AUTHOR]