This study compared femoral cartilage characteristics between age‐ and sex‐matched individuals with (n = 48, age = 22.8 ± 3.5 years; body mass index [BMI] = 33.1 ± 4.1 kg/m2) and without obesity (n = 48 age = 22.0 ± 2.6 years; BMI = 21.7 ± 1.7 kg/m2) and evaluated the associations between body composition, quadriceps function, and gait kinetics with femoral cartilage characteristics. Medial and lateral femoral cartilage thickness, medial:lateral thickness ratio and medial and lateral cartilage echo intensity were measured using ultrasound imaging. Body composition was assessed using air displacement plethysmography. Quadriceps function was assessed via maximal isometric knee extension. Three‐dimensional gait biomechanics were recorded to extract peak external knee flexion and adduction moments, and peak loading rate of the vertical ground reaction force. Cartilage outcomes were compared between groups using one‐way multivariate analysis of variance. Stepwise moderated regression evaluated the association between body composition, quadriceps function, and gait kinetics with femoral cartilage outcomes in individuals with and without obesity. Medial (75.24 vs 65.84; P < .001, d = 1.02) and lateral (58.81 vs 52.22; P < .001, d = 0.78) femoral cartilage echo intensity were higher in individuals with compared with those without obesity. A higher body fat percentage was associated with higher medial and lateral cartilage echo intensity (ΔR2 = 0.09‐0.12) in individuals with obesity. A higher knee adduction moment was associated with a larger medial:lateral thickness ratio (ΔR2 = 0.09) in individuals without obesity. No associations were found between quadriceps function and cartilage outcomes. These findings suggest that high body fat in adults with obesity is associated with cartilage echo intensity. The obese body mass index was also associated with a lack of a positive relationship between cartilage thickness and joint loading during walking.

Purpose Prader–Willi Syndrome (PWS) is a form of congenital obesity characterized by excessive body fat, hypotonia, muscle weakness, and physical/cognitive disability. However, the sources of muscle dysfunction and their contribution to mobility are unclear. The purposes of this study were to 1) compare plantar flexor function between adults with and without PWS; and 2) to examine the relationship between plantar flexor function and gait speed in adults with PWS. Methods Participants included 10 adults with PWS, 10 adults without PWS and with obesity, and 10 adults without PWS and without obesity (matched on age and sex). Plantar flexor function was assessed using isokinetic dynamometry (peak torque [PT], early/late rate of torque development [RTD]), Hoffman reflex (H/M ratio), ultrasound imaging (cross-sectional area [CSA], echo intensity, pennation angle, and fascicle length), and peak propulsive force and plantar flexor moment during gait. Outcomes were compared between groups using one-way MANOVA. Associations between plantar flexor outcomes and gait speed were assessed using Pearson correlation in the PWS group. Results Adults with PWS had lower absolute and normalized early RTD, and lower H/M ratio than controls with and without obesity; lower absolute PT and late RTD than controls with obesity (all P < 0.05). Cross-sectional area, propulsive force, and plantarflexor moment were lower, and echo intensity was higher, in adults with PWS compared with controls without obesity (all P < 0.05). Greater absolute PT (r = 0.64), absolute early RTD (r = 0.62), absolute late RTD (r = 0.64), gastrocnemii CSA (r = 0.55), and propulsive force (r = 0.58) were associated with faster gait speed (all P < 0.05). Conclusions Adults with PWS have impaired plantar flexor function likely attributable to reduced neuromuscular function and altered muscle morphology, which are associated with slower gait speeds.

Research has identified an increased risk of lower extremity injury postconcussion, which may be due to aberrant biomechanics during dynamic tasks. The purpose of this study was to compare the drop landing biomechanics between individuals with and without a concussion history. Twenty-five individuals with and 25 without a concussion history were matched on age (±3 y), sex, and body mass index (±1 kg/m2). Three-dimensional landing biomechanics were recorded to obtain dependent variables (peak vertical ground reaction force, loading rate, knee flexion angle and external moment, knee abduction angle and external moment, and knee flexion and abduction angle at ground contact). A 1-way multivariate analysis of variance compared outcomes between groups. There was no difference in drop landing biomechanics between individuals with and without a concussion history (F10,39 = 0.460, P = .877, Wilk Λ= .918). There was an effect of time since concussion on knee flexion characteristics. Time since most recent concussion explained a significant amount of variation in both peak (ΔR2 = .177, β = −0.305, ΔP = .046) and initial ground contact (ΔR2 = .292, β = −0.204, ΔP = .008) knee flexion angle after covarying for sex and body mass index. Therefore, time since concussion should be considered when evaluating biomechanical patterns.

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