Michael A. Samaan

Background: Hereditary spastic paraplegia (HSP) is a rare genetic neurodegenerative disorder characterized by progressive lower-extremity spasticity, weakness, and gait impairment resulting from corticospinal tract degeneration. With no disease-modifying therapies available, novel strategies to improve motor function are needed. Transcutaneous spinal cord stimulation (tSCS) is a non-invasive neuromodulation approach that may improve motor function but has not been prospectively evaluated in HSP. This study will assess the safety, feasibility, and preliminary efficacy of repeated tSCS in adults with HSP. Methods and analysis: This prospective, open-label, single-arm pilot trial will enroll 15 adults with HSP. Participants will receive 16 tSCS sessions over 8 weeks targeting the lower thoracic and upper lumbar vertebral levels, followed by an 8-week follow-up. Outcomes will assess gait performance, spasticity, disease severity, mobility, walking endurance, muscle strength, 3D gait biomechanics, electromyography, and HSP-specific patient-reported measures. Exploratory blood-based neurodegenerative biomarkers and metabolomic and lipidomic profiles will investigate potential biological correlates of treatment response. Assessments will occur at baseline and weeks 4, 8, and 16. Feasibility and safety will be evaluated through recruitment, retention, adherence, and adverse events.

Background: People with Marfan syndrome (MFS) exhibit a high incidence of hip joint pain and earlier onset of osteoarthritis than those without MFS. Imaging-related biomarkers of hip joint health that provide an earlier indication of hip cartilage degeneration in the MFS population have yet to be assessed. Purpose: We sought to determine whether people with MFS exhibit biochemical alterations of proteoglycan content and collagen structure within the hip joint cartilage compared to individuals without MFS as documented by quantitative magnetic resonance imaging (MRI) including both T1ρ and T2 mapping. Methods: Fourteen individuals with MFS and 14 healthy, asymptomatic controls matched for age, sex, and body mass index underwent radiographic imaging and unilateral hip quantitative MRI including both T1ρ and T2 mapping to evaluate cartilage proteoglycan content and collagen structure. Results: People with MFS showed significantly higher T1ρ values in the anterior superior acetabular cartilage compared to the asymptomatic controls. No significant between-group differences were noted in the femoral T1ρ values or in any of the T2-related values. Conclusion: This cross-sectional, observational study found elevated anterior superior acetabular cartilage T1ρ values, indicating a lower proteoglycan content within this specific sub-region, in individuals with MFS. The anterior superior acetabular cartilage may be prone to degeneration and may contribute to the high rates of early onset osteoarthritis observed in the MFS population. Our results suggest T1ρ cartilage imaging may be a potential biomarker of early cartilage degradation in the MFS population. Clinically, T1ρ imaging may allow for better informed decisions regarding interventional timing to prevent the onset and progression of hip osteoarthritis in individuals with MFS. Level of Evidence: Level III, prognostic study

Marfan syndrome (MFS) is a connective tissue disorder caused by structural changes in fibrillin-1 and is associated with muscle weakness and joint pain. The understanding of lower extremity (LE) joint mechanics associated with joint pain in people with MFS is limited. The goal of this study was to assess LE joint mechanics during the sit-to-stand (STS) task in people with MFS compared with asymptomatic controls. Sixteen people with MFS and 16 sex- and body mass index-matched controls were tested in this study. All participants performed the STS task at a self-selected speed. Peak LE joint extensor moments, moment impulses, moment durations, time to task completion, total support moment (TSM), and each joint’s contribution to the TSM were evaluated. People with MFS took longer to perform the task and exhibited lower peak knee extensor moments and higher peak ankle plantar flexor moments compared with controls. Higher LE joint extensor moments impulses and moment durations were observed in people with MFS. People with MFS performed the STS task using a higher TSM with higher ankle contributions to the TSM. People with MFS exhibit altered LE joint mechanics during the STS task and utilize a more ankle joint dominant strategy.

Background: Socioeconomic factors significantly influence health outcomes in older adults, yet their impact on specific aspects of mobility remains unclear. This study investigates the relationship between area-level socioeconomic disadvantage and mobility health in older adults. Methods: We conducted a cross-sectional study of 110 community-dwelling older adults recruited and collected using voluntary response sampling at eight health fairs across rural Southeast Alabama in 2022–2024 (60 ± 16 years, 80% female). Area-level socioeconomic status was measured using the Area Deprivation Index (ADI), a validated composite measure of neighborhood disadvantage. Mobility was assessed using the Instrumented Timed Up and Go (iTUG) test and the Instrumented Five Times Sit-to-Stand (i5TSTS) test. Kruskal–Wallis tests and general linear models in SAS 9.4 analyzed the relationship between ADI and mobility measures. Results: Higher ADI scores were significantly associated with poorer performance on the i5TSTS test (p = 0.0004). While overall iTUG duration did not differ significantly across ADI groups, the sit-to-stand phase of the iTUG showed a significant relationship with ADI (p = 0.0026). These associations remained significant after adjusting for age, weight, race, and education level. Conclusions: These findings suggest that neighborhood context plays a crucial role in mobility health, particularly in functions related to postural transitions. Clinicians should consider area-level disadvantage when screening for mobility limitations and may need to prioritize sit-to-stand interventions for patients living in high-deprivation areas.

After anterior cruciate ligament reconstruction (ACLR), individuals often demonstrate asymmetrical lower-extremity biomechanics and suboptimal vertical jump performance. These deficits have negative implications for reinjury risk and ability to return to sport. This study aims to quantify asymmetrical lower-extremity (hip, knee, and ankle) biomechanics and identify modifiable impairments contributing to altered knee joint mechanics and vertical jump performance after ACLR. Twenty-four individuals (19.6 [3.4] mo post-ACLR) performed isometric and isokinetic knee extensor strength testing followed by single- and double-limb vertical jumps using 3D motion capture. We found no differences in lower-extremity kinematics but did observe reduced peak knee extensor moment and joint power in the ACL-involved limb during both jumps. Furthermore, quadriceps peak torque and rate of torque development were significantly associated with propulsive knee joint power and vertical jump height. The findings from this study highlight that individuals demonstrate persistent knee joint underloading 2 years following ACLR that is related to inadequate quadriceps peak torque and rate of torque development. Clinicians should prioritize restoration of quadriceps peak torque and rate of torque development to improve knee joint kinetics, vertical jump performance, and overall readiness to return to competitive sport.

Knee health constitutes a pivotal determinant of locomotor function and overall mobility throughout the healthspan. Impairments in knee function lead to a series of biomechanical and physiological alterations that pose substantial public health challenges and economic burdens worldwide. This review synthesizes evidence that delineates the complex and multifaceted relationship between knee health and mobility, emphasizing the interplay across various domains in adult populations. Knee health is conceptualized as a dynamic, interconnected system whereby structural integrity, neuromuscular mechanisms, biomechanical adaptations, and functional mobility are intricately interrelated through cascades of mechanistic processes operating across different temporal stages. A comprehensive understanding of these interrelationships is necessary for developing precise and targeted interventions that aim to preserve mobility and functional independence throughout the healthspan.

This study aimed to (1) demonstrate the intra- and interrater reliability of quadriceps (QUADS) and hamstring (HAMS) mineral-free lean (MFL) mass measures using DXA scanning, (2) determine the association of total thigh MFL mass measures with MFL mass measures of the hamstrings and quadriceps combined and (3) analyze the association between total thigh MFL mass and total body MFL mass measures. A total of 80 young children (aged 5 to 11 yrs) participated and unique regions of interest were created using custom analysis software with manual tracing of the QUADS, HAMS, and total thigh MFL mass measures. Repeated-measure analysis of variance was used to determine if there were significant differences among the MFL measures while intraclass correlation coefficients (ICC), coefficients of variation (CV), and regression analysis were used to determine the intra- and interrater reliability and the explained variance in the association among MFL mass measures. The right interrater QUADS MFL mass was the only significant group mean difference, and ICCs between (≥0.961) and within (≥0.919) raters were high for all MFL measures with low variation across all MFL measures (≤6.13%). The explained variance was 92.5% and 96.3% for the between-investigator analyses of the right and left total thigh MFL mass measures, respectively. Furthermore, 97.5% of the variance in total body MFL mass was explained by the total thigh MFL mass. DXA MFL mass measures of the QUADS, HAMS and total thigh can be confidently used in young children and may provide an alternative to CT or MRI scanning when assessing changes in MFL cross-sectional area or volume measures due to disease progression, training and rehabilitative strategies.

Muscle strength can substantially influence knee joint loading, stability, and cartilage biomechanics, all of which are important factors in the onset and progression of knee osteoarthritis (KOA). Noninvasive rehabilitation methods, such as gait modifications, are suggested to effectively alter knee joint loading, potentially helping to prevent or slow KOA progression. However, no studies to date have assessed if reduced lower limb muscle strength can influence the effects of rehabilitation exercises such as gait modifications. This study aimed to reveal how reducing the strength of three lower limb muscle groups (knee extensors, hip abductors, and ankle extensors) impacts the effects of gait modifications (Toe‐out, Toe‐in, and Wide gait) on knee cartilage stresses. We analyzed motion and ground reaction force data from seven healthy male participants using a musculoskeletal‐finite element workflow, where we systematically reduced the isometric strength of the selected muscle groups in the musculoskeletal models. Our findings indicate that reductions in hip abductor and ankle extensor strength had the most pronounced impact on the effects of gait modifications on cartilage mechanics (maximum decrease of 6 percentage points (PP) in the changes of maximum principal stress). Overall, Toe‐out gait was least affected by reduced muscle strength compared to other gait styles, although responses varied greatly between participants (0–14 percentage point differences). This study emphasizes the importance of considering participant‐specific muscle strengths when designing personalized rehabilitation strategies such as gait modifications and provides theoretical insights into optimizing rehabilitation exercises for managing KOA based on a given motion and joint kinetics.