Evaluation of the relationship between truss/windlass mechanisms and foot stiffness while walking.

BACKGROUND: The truss/windlass coefficients ware reported as a surrogate parameter for foot stiffness while walking. However, the construct validity and reliability of whether the truss/windlass coefficients reflect foot stiffness have not been sufficiently validated. This study validated the truss/windlass coefficient reflects the construct validity and reliability of foot stiffness. METHODS: Participants were 25 healthy young males (21.6 ± 0.7 years). Foot stiffness was assessed using Simplified Foot Stiffness. It was determined by dividing the difference in foot load between sitting and standing by the rate of change in navicular height. The truss/windlass coefficient was calculated as the behavior of the foot arch during middle to late stance. To assess the reliability of each parameter, intraclass correlation coefficients (ICC 1.1) and Bland-Altman analysis were used, and Spearman's rank correlation coefficients were used to determine construct validity. RESULTS: The truss coefficient (ICC1.1 0.86) and Simplified Foot Stiffness (ICC1.1 0.87) demonstrated high reliability and no systematic error. However, the windlass coefficient (ICC1.1 0.73) demonstrated moderate reliability and proportional error. Furthermore, the truss coefficient had a significant positive correlation with Simplified Foot Stiffness (r = 0.504; p < 0.01), whereas the windlass coefficient did not (r = 0.06; p = 0.67). CONCLUSION: The truss coefficient was proposed as a highly reliable parameter that reflects foot stiffness. However, the windlass coefficient has a proportional error, despite being moderately reliable.

Improvement of muscle quality assessed using the phase angle is influenced by recovery of knee extension strength in patients with hip fractures.

BACKGROUND AND AIMS: Studies reported that knee extension strength on the operated side in patients with hip fractures was not recovered to the level on the non-operated side 6 months after surgery or later. In a cross-sectional study, we revealed that a reduction in isometric knee extension muscle strength on the operated side in patients with hip fractures approximately 6 months after surgery was associated with not only a reduction in skeletal muscle mass but also a reduction in muscle quality, characterized by a reduction in the phase angle (PhA). Furthermore, the mechanisms of knee extension strength improvement can be clarified in more detail using the minimal significant change as the index of recovery. However, no longitudinal studies have examined the factors for knee extension strength improvement based on the minimal significant change in patients with hip fractures 6 months after surgery. This study aimed to longitudinally examine the factors influencing the recovery of knee extension strength based on the minimal significant change in patients with hip fractures between 2 weeks and approximately 6 months after surgery. METHODS: In this study, the outcomes used were basic and medical information, PhA, skeletal muscle index (SMI), pain, one-leg standing time, movement control during one-leg standing, and walking speed. For PhA, SMI, pain, one-leg standing time, movement control during one-leg standing, and walking speed, the amount of change was calculated by subtracting the data at 2 weeks from the data at 6 months. Group classification was determined by dividing the patients into two groups using a previous study as a reference: recovery group if the knee extension strength value approximately 6 months after surgery minus that 2 weeks after surgery was ≥3.3 kgf and non-recovery group if the value was <3.3 kgf. Logistic regression analysis was performed to explore the association between the recovery and non-recovery groups. RESULTS: The recovery group contained 55 patients, while the non-recovery group comprised 35 patients. The only significant factor associated with knee extension muscle strength in the recovery group was the amount of change in PhA. The odds ratio for the amount of change in PhA was 2.26. The discrimination rate of the model was 62.5%. CONCLUSIONS: Our results suggest that recovery of knee extension strength in patients with hip fractures after surgery was mainly because of improvements in muscle quality, not improvements in muscle mass or pain.

Sex differences in pelvis, thigh, and shank coordination during walking.

Differences in lower limb kinematics between males and females during functional activities may be attributed to sex differences in the incidence of patellofemoral pain, which is more common in females. To better comprehend the knee joint motion, it is necessary to understand both inter-segmental coordination patterns and angular amplitude. This exploratory study aimed to assess sex differences in pelvis-thigh and thigh-shank coordination patterns in the frontal and horizontal planes during walking. Data regarding the kinematic characteristics of the pelvis, thigh, and shank segments were collected from 26 males and 26 females performing walking at self-selected speeds using a 3D motion capture system. Furthermore, we compared the kinematics of the pelvis, thigh, and shank during walking as well as the pelvis-thigh and thigh-shank coordination patterns in the frontal and horizontal planes during the stance phase between males and females. Compared to males, females had greater thigh adduction (p < 0.001) and internal rotation (p < 0.001) throughout the stance phase; significantly greater frequency of the pelvis-thigh anti-phase pattern in the frontal plane in the early (p = 0.002) and mid-stance (p = 0.003); and significantly greater thigh-shank anti-phase pattern in the frontal plane in the early (p = 0.001) and mid-stance (p = 0.015). These results suggest the presence of sex differences in the inter-segmental coordination of the pelvis and lower limb during walking. However, as this study could not determine a causal relationship between female sex and knee joint injury, further longitudinal studies are needed to determine the effects of differences in coordination patterns on the pathophysiology of the injury and pain generation.

Effects of Gluteus Maximus Muscle Activity and Pelvic Width on Dynamic Frontal Plane Hip Joint Stiffness During Gait in Healthy Young Women.

CONTEXT: Excessive hip adduction and internal rotation are abnormal movements that may lead to the onset and progression of patellofemoral pain. Previous studies have reported that lower dynamic frontal plane hip joint stiffness in the gait of women is associated with the magnitude of hip adduction and internal rotation angles. However, the factors contributing to the lack of dynamic frontal plane hip joint stiffness in the gait of young women are unclear. This study aims to investigate the factors affecting dynamic frontal plane hip joint stiffness during the weight-acceptance phase of the gait of healthy young women. DESIGN: Cross-sectional study. METHODS: This study included 30 healthy women between the ages of 18 and 30 years. The pelvic width/femur length ratio was calculated by dividing the pelvic width by the femur length. Data on hip kinematics and kinetics and activation of the gluteus maximus and medius, tensor fasciae latae, and adductor longus muscles during gait were collected using a motion capture system, force plates, and surface electromyography. Stepwise multiple regression analysis was conducted to determine the extent to which each independent factor affected dynamic frontal plane hip joint stiffness. RESULTS: In healthy young women, decreased dynamic frontal plane hip joint stiffness was associated with decreased muscle activity of the gluteus maximus during the gait, as well as greater pelvic width/femur length ratio. CONCLUSIONS: Women with a relatively great pelvic width relative to femur length may have more difficulty in producing dynamic frontal plane hip joint stiffness. However, increasing the muscle activity of the gluteus maximus may contribute to increased dynamic frontal plane hip joint stiffness.

Not only muscle mass but also muscle quality is associated with knee extension muscle strength in patients with hip fractures.

Our results revealed that the decrease in isometric knee extension muscle strength on the operated and nonoperated sides in patients with hip fractures was associated with not only a decrease in skeletal muscle mass but also a decrease in muscle quality, characterized by a decreased PhA. PURPOSE: This study aimed to assess the relationship between isometric knee extension muscle strength on the operated or nonoperated sides and PhA in patients with hip fractures at approximately 6 months postoperatively. METHODS: This study was a cross-sectional study. Skeletal muscle index (SMI), PhA, knee extension muscle strength on the operated and nonoperated sides, and other physical function variables were assessed at approximately 6 months postoperatively. To identify predictors of knee extension muscle strength on the operated and nonoperated sides, hierarchical multiple regression analysis was performed. RESULTS: A total of 90 patients with hip fractures were included (mean age, 80.1 ± 6.9 years). SMI (0.45) and PhA on the operated side (0.27) were the significant associated factors extracted for isometric knee extension muscle strength on the operated side (standardized partial regression coefficients), independent of age, sex, and body mass index (BMI). Movement control during one-leg standing on the nonoperated side (0.26), SMI (0.32), and PhA on the nonoperated side (0.40) were the significant associated factors extracted for isometric knee extension muscle strength on the nonoperated side, independent of age, sex and BMI. CONCLUSIONS: Our results revealed that the decrease in isometric knee extension muscle strength on the operated and nonoperated sides in patients with hip fractures at approximately 6 months postoperatively was associated with not only a decrease in skeletal muscle mass but also a decrease in muscle quality, characterized by a decreased PhA.

Reduced upper and lower limb muscle strengths without reduced skeletal muscle in elderly patients with heart failure.

Objective: This study aimed to characterize the muscle strength and skeletal muscle mass of patients with heart failure by investigating hand-grip strength, five times sit-to-stand (5STS) results, and skeletal muscle mass index (SMI). Materials and Methods: Muscle strength was assessed based on hand-grip strength and 5STS, while skeletal muscle mass was assessed using a bioelectrical impedance analyzer. Hierarchical logistic regression analysis was performed to explore the association between patients with heart failure and healthy elderly individuals. Results: Hierarchical logistic regression analysis was performed to examine the muscle strength and skeletal muscle mass characteristics in patients with heart failure. Hand-grip strength and 5STS responses but not SMI outcomes differed significantly between the two groups. The results of the hierarchical logistic regression analysis revealed that the hand-grip strength and 5STS were significant predictors of heart failure. The odds ratios for hand-grip strength and 5STS were 1.44 and 0.53, respectively. Conclusion: Our results suggested that upper and lower limb muscle strengths (handgrip strength and 5STS) in elderly patients with heart failure worsened significantly without a decrease in skeletal muscle mass.

The effect of lumbopelvic region rotation relative flexibility on thorax-pelvis and pelvis-femur coordination during walking.

BACKGROUND: Lumbopelvic region rotation relative flexibility (LRRF), which is defined as lumbopelvic region that is relatively less stiffness than the hip region, is associated with low back pain (LBP) symptoms. However, how LRRF is influenced by lumbopelvic region motion during walking is unclear. RESEARCH QUESTION: What is the influence of LBP and LRRF on coordination patterns of the thorax, pelvis, and femur during walking? METHODS: The presence of LRRF was determined based on whether the lumbopelvic rotation occurred in the first 50% of knee flexion or hip external rotation movement. Participants with LBP and LRRF were classified into the LBP group. Participants with LRRF but without LBP were classified into the early pelvis rotation (ROT) group, and those without LBP and relative flexibility were classified as controls. The thorax-pelvis coordination and pelvis-femur coordination during the stance cycles were calculated from the segmental angles obtained by three-dimensional motion analysis using a modified vector coding technique. RESULTS: In the sagittal plane, the thorax-pelvis coordination of the LBP group showed more anti-phase patterns at both the early stance and midstance compared with controls and the ROT group. In the sagittal and horizontal planes, pelvis-femur coordination of the LBP and ROT groups showed more in-phase patterns during the early stance and midstance compared with controls. SIGNIFICANCE: Regardless of LBP, the presence of LRRF alters the intersegmental coordination during walking. In individuals with LRRF, stiffness of the hip may increase during walking. People who have LRRF without LBP may develop LBP in the future, and it is important for prevention to identify these differences in kinematics during walking.

Effects of core stability on shoulder and spine kinematics during upper limb elevation: A sex-specific analysis.

BACKGROUND: Upper limb elevation begins with core stabilization, but the effects of core stability on shoulder and spine kinematics are unknown. Sex differences also exist in shoulder kinematics and core stability. OBJECTIVE: To clarify the effects of core stability on shoulder and spine kinematics during upper limb elevation by taking sex into account. DESIGN: Cross-sectional. METHODS: The Sahrmann Core Stability Test, lumbar spine motor control test battery, and Y Balance Test (lower and upper quarters) were performed in 50 healthy young adults. For each test, a principal component (PC) analysis was conducted according to sex; the overall core stability score was calculated. The top and bottom third of the PC scores were defined as high and low score groups, respectively (each group: nine males and eight females). Shoulder and spine kinematics during upper limb elevation were compared separately for males and females. RESULTS: Spinal extension was greater in the low score group by a maximum of 1.9° in males (P < .001; η2 = 0.068) and 1.6° in females (P < .001; η2 = 0.141). In the low score group of females, the scapular posterior tilt was a maximum of 5.6° smaller (P < .001; η2 = 0.221) and glenohumeral elevation was a maximum of 4.5° larger (P < .001; η2 = 0.113) than the high score group of females. CONCLUSION: Core stability affected spine and female scapular and glenohumeral kinematics during upper limb elevation. Core stability may be one of the potential contributors to shoulder kinematics, particularly in females.

Movement control during one-leg standing is important for the bone mineral density maintenance or improvement.

INTRODUCTION: Both hip fracture and bone mineral density (BMD) decline on the non-fractured side are more likely to occur within 1 year. However, there are no longitudinal study reports on the factors associated with BMD maintenance or improvement within the first year after hip fracture. This study aimed to investigate the factors influencing the neck BMD maintenance or improvement in patients with hip fractures from within 2 weeks-6 months after surgery. MATERIALS AND METHODS: Patients were hip fracture after surgery and were divided into two groups: Among neck BMD changes (6 months minus 2 weeks after surgery) were calculated. Based on among neck BMD change, patients were classified into the BMD maintenance or improvement (change ≥ 0) and the BMD decrease groups (change < 0). Propensity score matching was performed to adjust for confounding factors. To predict the factors affecting neck BMD, hierarchical logistic regression analysis was performed. The dependent variable was the BMD maintenance or improvement group and the BMD decrease group. The independent variables were basic and medical information, and physical functions. RESULTS: The hierarchical logistic regression analysis results showed that movement control during one-leg standing affected femoral neck BMD independently from age, sex. The odds ratio for movement control during one-leg standing was 8.22. The discrimination rate of the model was 69.7%. CONCLUSION: This study suggested that adequate movement control during one-leg standing is important to maintain or improve neck BMD.

Association of muscle mass and quality with hand grip strength in elderly patients with heart failure.

In patients with heart failure, it is unknown whether the extracellular water (ECW)/intracellular water (ICW) ratio is associated with muscle strength, and thus, it is not well understood whether poor muscle quality contributes to muscular weakness. This study examined the relationship among hand grip strength, skeletal muscle mass index (SMI), and upper limb ECW/ICW ratio in patients with heart failure. This study followed a cross-sectional design. Demographic data, medical information, and hand grip strength were collected. The SMI and ECW/ICW ratio were measured using bio-impedance analysis (BIA). Hierarchical multiple regression analysis was conducted to identify factors associated with hand grip strength. 51 patients with heart failure were analyzed for this study (mean age 84.58 ± 7.18). Hierarchical multiple regression analysis identified SMI as well as upper limb ECW/ICW ratio as factors associated with hand grip strength, independent of age, sex, body mass index, and Life Space Assessment scores. Standardized partial regression coefficients representing the magnitude of involvement of each independent variable were 0.33 and - 0.16. The coefficient of determination adjusted for degrees of freedom (R2), representing the contribution rate of the regression equation, was 0.830. We revealed that loss of hand grip strength in patients with heart failure is associated with not only with a decrease in skeletal muscle mass, but also with a decline in muscle quality, characterized by an increased upper limb ECW/ICW ratio. BIA is a simple and useful method to measure the ECW/ICW ratio, and in turn, the muscle quality, in patients with heart failure.

Interactive effects of exercise and sleep on frailty severity in community-dwelling older adults: a cross-sectional study.

Objectives: This study examined the effects of the interaction between exercise and sleep on frailty severity in community-dwelling older adults. Materials and Methods: This was a cross-sectional study. Data were collected in July 2019. In total, 2021 adults participated who responded to a questionnaire. Among them, 672 participants (317 men and 355 women) with valid responses were included in the analysis. Ordinal logistic regression analysis was performed to examine the association between frailty severity and the interaction between exercise and sleep. The dependent variable represents three different levels of frailty. The independent variables included basic information and interaction between exercise and sleep. Results: The results of ordinal logistic regression analysis (odds ratio [OR]) showed that the period from the start of exercise (OR=0.96), age (OR=1.00 for participants in their 60 s, OR=1.65 for those in their 70s, and OR=3.13 for those aged >80 years), poor subjective health perception (OR=2.12), poor quality of sleep (OR=1.88), stress (OR=1.62), and exercise-sleep interaction (OR=1.00 based on good-exercise-good-sleep interaction, OR=3.09 poor-exercise-good-sleep interaction, and OR=3.50 poor-exercise-poor-sleep interaction) significantly contributed to the model. The Nagelkerke coefficient of determination adjusted for degrees-of-freedom (R2), which represents the contribution rate of the regression equation, was 0.334. Conclusions: Our results suggest that a combination of good exercise and good sleep is needed to prevent frailty progression in community-dwelling older adults.

Relationship Among 3 Different Core Stability Tests in Healthy Young Adults: Validity and Gender Differences.

CONTEXT: Core stability is important for preventing injury and improving performance. Although various tests for evaluating core stability have been reported to date, information on their relationship and the effect of gender differences is limited. This study aimed to (1) identify correlations among the 3 core stability tests and to examine the validity of each test and (2) identify gender differences in the test relationship and determine whether gender influenced test selection. DESIGN: Cross-sectional study. METHODS: Fifty-one healthy volunteers (27 men and 24 women) participated in the study. The participants underwent the following 3 tests: Sahrmann Core Stability Test (SCST), the lumbar spine motor control tests battery (MCBT), and Y Balance Test (YBT). Each parameter was analyzed according to all parameters and gender using the Spearman rank correlation coefficient. RESULTS: Overall, there was a strong positive correlation between SCST and MCBT and moderate positive correlations between SCST and YBT and between MCBT and YBT. Conversely, gender-specific analyses revealed no significant correlations between YBT and SCST and between YBT and MCBT in women, although significantly strong correlations were found among all tests in men. CONCLUSION: Although these 3 tests evaluated interrelated functions and may be valid as core stability tests, the results should be carefully interpreted when performing YBT in women.

Differences in the effects of BMI on bone microstructure between loaded and unloaded bones assessed by HR-pQCT in Japanese postmenopausal women.

OBJECTIVES: The relationship between weight-related load and bone mineral density (BMD)/bone microstructure under normal load conditions using high-resolution peripheral quantitative computed tomography (HR-pQCT) remains unconfirmed. The study aims to investigate the differences in effect of body mass index (BMI) on BMD/bone microstructure of loaded and unloaded bones, respectively, in Japanese postmenopausal women. METHODS: Fifty-seven postmenopausal women underwent HR-pQCT on the tibia and radius. Correlation analysis, principal component (PC) analysis, and hierarchical multiple regression were performed to examine the relationship between BMI and HR-pQCT parameters. RESULTS: Several microstructural parameters of the tibia and radius correlated with BMI through a simple correlation analysis, and these relationships remained unchanged even with an age-adjusted partial correlation analysis. PC analysis was conducted using seven bone microstructure parameters. The first PC (PC1) reflected all parameters of trabecular and cortical bone microstructures, except for cortical porosity, whereas the second PC (PC2) reflected only cortical bone microstructure. Hierarchical multiple regression analysis indicated that BMI was more strongly related to BMD/bone microstructure in the tibia than in the radius. Furthermore, BMI was associated with trabecular/cortical BMD, and PC1 (not PC2) of the tibia and radius. Thus, BMI was strongly related to the trabecular bone microstructure rather than the cortical bone microstructure. CONCLUSIONS: Our data confirmed that BMI is associated with volumetric BMD and trabecular bone microstructure parameters in the tibia and radius. However, although BMI may be more related to HR-pQCT parameters in the tibia than in the radius, the magnitude of association is modest.

Relationship between forward propulsion and foot motion during gait in healthy young adults.

The foot contributes to propulsion and postural stability function by changing its morphology during walking through the truss/windlass mechanisms. We quantified the truss mechanism regarding foot stiffness and the windlass mechanism regarding the movement coordination between the foot arch and metatarsophalangeal (MTP) joint. We aimed to clarify the relationship of these mechanisms with propulsive force and static foot alignment. Forty-eight healthy young adults participated and walked at a comfortable speed. The ground reaction force (GRF), ankle power, and sagittal plane motion of the foot arch and MTP joint were recorded using a three-dimensional motion analysis system. The vertical GRF and foot arch motion were used to quantify foot stiffness as the truss coefficient, and the foot arch and first MTP joint were used to quantify movement coordination as the windlass coefficient. The Foot Posture Index (FPI) and arch height index (AHI) were used to assess static foot alignment. A canonical correlation analysis was performed using the foot- and gait-related index group, and then a single-correlation analysis was performed. The canonical correlation analysis showed that a composite variable consisting of FPI, AHI, and the truss coefficient was related to the anterior GRF (A-GRF) and ankle power. The truss coefficient was positively correlated with A-GRF and ankle power, whereas the windlass coefficient was positively correlated with ankle power. Therefore, the truss and windlass coefficients can be used as indices to evaluate foot function, suggesting that maintaining foot stiffness and foot arch coordination with the first MTP joint is important for propulsion.

Association between movement control during one-leg standing and femoral BMD in patients with hip fractures.

INTRODUCTION: Prior studies have focused only on the temporal component of one-leg standing, no reports have examined the relationship between the qualitative components of one-leg standing and femoral BMD. Thus, this study investigated whether quality (i.e., movement control) of one-leg standing also associated femoral BMD. MATERIALS AND METHODS: A total of 80 patients with unilateral hip fracture were included in a cross-sectional study. Basic and medical information and physical functions including movement control during one-leg standing were assessed at admission and 2 weeks after surgery, respectively. Hierarchical multiple regression analysis was performed to identify predictors of femoral BMDs on the non-fractured side. Dependent variables included femoral neck and total hip BMDs in models 1 and 2, respectively. RESULTS: Hierarchical multiple regression analysis (standardized partial regression coefficients) in model 1 identified age (- 0.18), sex (0.38), body mass index (BMI) (0.41), movement control during one-leg standing on the non-fractured side (0.19), and life-space assessment (0.17) as factors associating femoral neck BMD. Meanwhile, hierarchical multiple regression analysis (standardized partial regression coefficients) in model 2 identified age (- 0.12), sex (0.36), BMI (0.37), and movement control during one-leg standing on the non-fractured side (0.25) as factors associating total hip BMD. The coefficients of determination adjusted for degrees of freedom (R2) were 0.529 and 0.470 for models 1 and 2, respectively. CONCLUSION: Our results suggest that improving movement control during one-leg standing may be important for maintaining and improving femoral BMD on the non-fractured side.

Daily activity relates to not only femoral bone mineral density, but also hip structural analysis parameters: A cross-sectional observational study.

OBJECTIVES: Physical activity to maintain bone mass and strength is important for hip fracture prevention. We aim to investigate the relationship between physical performance/activity status and bone mineral density (BMD)/hip structural analysis (HSA) parameters among postmenopausal women in Japan. METHODS: Sixty-two postmenopausal women diagnosed with osteoporosis (mean age: 72.61 ± 7.43 years) were enrolled in this cross-sectional observational study. They were evaluated for BMD and HSA in the proximal femur by dual-energy X-ray absorptiometry and underwent several physical performance tests, the Geriatric Locomotive Function Scale of 25 questions (GLFS-25). Principal component analysis (PCA) was used to summarize data on the BMD/HSA parameters. Partial correlation analysis, multiple regression analysis, and structural equation modeling (SEM) were performed to investigate the relationship between physical performance/activity status and BMD/HSA parameters of the proximal femur. RESULTS: In a partial correlation analysis adjusted for age and body mass index (BMI), GLFS-25 scores were correlated with HSA parameter (|r| = 0.260-0.396, P < 0.05). Principal component 1 (PC1) calculated by PCA was interpreted as more reflective of bone strength based on the value of BMD/HSA parameters. The SEM results showed that the model created by the 3 questions (Q13, brisk walking; Q15, keep walking without rest; Q20, load-bearing tasks and housework) of the GLFS-25 had the best fit and was associated with the PC1 score (ß = -0.444, P = 0.001). CONCLUSIONS: The GLFS-25 score was associated with the BMD/HSA parameter, which may reflect the bone strength of the proximal femur as calculated by PCA.

Relationship Between Hip Frontal Dynamic Joint Stiffness and Frontal and Transverse Plane Hip Kinematics During Gait: Sex Differences.

CONTEXT: Previous studies have reported that the incidence of patellofemoral pain in women is 2.2 times higher than that in men. Lower hip frontal dynamic joint stiffness in women may be related to the magnitude of hip adduction and internal rotation associated with patellofemoral pain. OBJECTIVE: To identify sex differences in hip frontal dynamic joint stiffness and examine the relationship between hip frontal dynamic joint stiffness and hip adduction and internal rotation during gait. DESIGN: Cross-sectional study. SETTING: University campus. PARTICIPANTS: A total of 80 healthy volunteers (40 women and 40 men) participated in this study. INTERVENTION(S): Kinematic and kinetic data during gait were collected using a motion capture system and force plates. MAIN OUTCOME MEASURES: Hip frontal dynamic joint stiffness, hip adduction, and hip internal rotation were calculated during gait. RESULTS: Women demonstrated lower hip frontal dynamic joint stiffness than men during gait (P < .01). They also displayed decreased hip frontal dynamic joint stiffness associated with increased hip adduction (r = -.85, P < .001) and internal rotation (r = -.48, P < .001). Conversely, in men, decreased hip frontal dynamic joint stiffness was associated with increased hip adduction (r = -.74, P < .001) but not internal rotation (r = .17, P = .28). CONCLUSIONS: Sex differences between hip frontal dynamic joint stiffness and hip internal rotation during gait may contribute to the increased incidence of patellofemoral pain in women.

Effects of hypertonia on contracture development in rat spinal cord injury.

STUDY DESIGN: Experimental animal study. OBJECTIVES: Spastic hypertonia is originally believed to cause contractures from clinical observations. Botulinum toxin is effective for the treatment of spasticity and is widely used in patients who have joints with contractures. Using an established rat model with knee contractures after spinal cord injuries, we aimed to verify whether hypertonia contributes to contracture development, and the botulinum toxin improves structural changes in muscles and joint components responsible for contractures. SETTING: University laboratory in Japan. METHODS: To evaluate the effect of hypertonia on contracture development, the rats received botulinum toxin injections after spinal cord injuries. Knee extension motion was measured with a goniometer applying a standardized torque under anesthesia, and the contribution by muscle or non-muscle structures to contractures were calculated by measuring joint motion before and after the myotomies. We quantitatively measured the muscle atrophy, muscle fibrosis, and synovial intima length. RESULTS: Botulinum toxin injections significantly improved contractures, whereas did not completely prevent contracture development. Botulinum toxin was effective in improving the muscular factor, but little difference in the articular factor. Spinal cord injuries induced muscle atrophy, and botulinum toxin significantly accelerated muscle atrophy and fibrosis. The synovial intima length decreased significantly after spinal cord injuries, and botulinum toxin did not improve this shortening. CONCLUSIONS: This animal study provides new evidence that hypertonia is not the sole cause rather is the partial contributor of contractures after spinal cord injuries. Furthermore, botulinum toxin has adverse effects in the muscle.

Accumulation of advanced-glycation end products (AGEs) accelerates arthrogenic joint contracture in immobilized rat knee.

Joint mobility decreases in the elderly and in diabetics, this process is thought to be caused by accumulation of advanced-glycation end products (AGEs). Here, we aimed to elucidate the role of AGEs in joint contracture formation in rat knees. Rats were injected with ribose or saline into the knees twice weekly for 8 weeks. Pentosidine (AGE) levels were measured in the knee-joint tissues. After serial injections, rats were subjected to unilateral knee-joint immobilization in a flexion position for various periods. At day 21, the passive knee ranges of motions (ROMs) were measured. Knee joint histopathology were assessed, and the expression of fibrotic genes in the posterior joint capsules was examined using real-time PCR. Ribose injection induced a 7.0-fold increase in pentosidine levels relative to saline injection. Joint immobilization resulted in equal myogenic ROM restriction in both groups. Arthrogenic ROM restriction was greater with ribose injection in the immobilized joints (p < 0.05), but was not affected in nonimmobilized joints. Type-I (COL1A1) and type-III (COL3A1) collagen gene expression increased significantly in immobilized joints relative to nonimmobilized joints in the ribose group, but was not affected in the saline group. Ribose injection increased COL1A1 expression slightly and COL3A1 expression significantly in immobilized joints. Histologically, inflammatory changes appeared at day 3 of immobilization and peaked at day 7. These responses trended to be more severe and prolonged in the ribose group than in the saline group. Our data provide evidence for a causal relationship between AGEs and joint contracture formation following immobilization. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:854-863, 2018.