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Low back pain (LBP) and neck pain (NP) are common health problems worldwide. LBP often coexists with NP; however, the association between these pains remains unclear. The purpose of this study was to clarify the association between LBP and NP, focusing on dose-dependent effects. This study used a 3-year longitudinal cohort data of people living in disaster-stricken areas after the Great East Japan Earthquake (n = 2,118). LBP and NP were assessed at 4, 5, 6, and 7 years after the disaster. LBP was categorized according to its frequency. Multivariate logistic regression analyses were performed to assess the association between LBP and NP, and the effect of preceding LBP on the subsequent onset of NP, according to the frequency of LBP. LBP was significantly associated with NP, and the association was stronger with increased frequency of LBP. Adjusted odds ratios (95% confidence intervals) were 2.40 (1.71-3.37) for "1", 3.99 (2.82-5.66) for "2", and 6.08 (4.40-8.41) for "≥ 3" in frequency when the absence of LBP was used as a reference (p for trend < 0.001). Furthermore, preceding LBP was significantly associated with subsequent onset of NP, and the effect was stronger with increased frequency of LBP. Adjusted odds ratios (95% confidence intervals) were 2.44 (1.62-3.68) for "1" and 2.68 (1.77-4.05) for "≥ 2" in frequency when the absence of LBP was used as a reference (p for trend < 0.001). LBP is associated with NP in a dose-dependent manner. The association between LBP and NP should be considered to effectively treat these pains.

Shoulder pain is more common among survivors of natural disasters than the general population. This study aimed to examine the occurrence of shoulder pain, especially the association between prior and later shoulder pain episodes, in survivors living in coastal areas severely damaged by the Great East Japan Earthquake (GEJE) (n = 1,821) over a period of 5 years. The presence of shoulder pain was assessed at 2 (first period), 4 (second period), and 7 (third period) years after the disaster. Multiple logistic regression analyses were performed to assess the association between shoulder pain during the first and second periods and shoulder pain during the third period. Shoulder pain in the first period was significantly associated with shoulder pain in the third period [adjusted odds ratio (OR) 5.93; 95% confidence interval (CI) 4.06-8.66]. Furthermore, shoulder pain in the first and second periods was significantly associated with shoulder pain in the third period. With the absence of shoulder pain in both the first and second periods used as the reference, adjusted ORs for the presence of shoulder pain during each period and both periods were 4.58 (95% CI 3.17-6.62) and 15.54 (95% CI 8.38-28.84), respectively (P for trend < 0.001). Thus, prior shoulder pain was significantly associated with shoulder pain after 5 years among GEJE survivors, and the association was stronger as the number of prior shoulder pain episodes increased. This expertise should be shared with other expert teams to address the affected people and prepare for future disasters.

Communication between parents and their children's coaches is important for children's sports activities, but the relationship between parents and coaches is not well understood. It is possible that parents feel a lack of communication with coaches, which could be due to parents' experience with sports activities or the social environment of the team. This study aimed to elucidate the characteristics of parents who feel a lack of communication with their children's coaches of youth sports. A cross-sectional study was conducted on parents of young athletes (n = 6,641) and multivariate logistic regression analyses were performed to assess factors related to parents' feeling of a lack of communication with their children's coaches. Among the respondents, 29.4% of parents felt a lack of communication with their children's coaches. The factors related to the parents' feeling were a shorter duration of their children playing the present sport, an absence of experience playing the same sport as their children or playing in a team with high competition level, dissatisfaction with their children's attitude towards sports activities, and an awareness of verbal and/or physical abuse by the coaches and bullying by the teammates in their children's team. Parents' previous sports experience and awareness of interpersonal violence in their children's team were associated with their feeling of a lack of communication with coaches. Educating parents on the sport and their roles in youth sport is necessary to make appropriate mutual communication between parents and coaches, which could lead to better circumstances for young athletes.

Martial arts, such as judo, kendo, and karate, are popular worldwide, not only among adults but also among children and adolescents. Although low back pain (LBP) is considered to be a common problem in these sports, it has been scarcely studied, especially in young athletes. The purpose of this study was to elucidate the point prevalence of and factors related to LBP among school-aged athletes in judo, kendo, and karate. A cross-sectional study was conducted in school-aged athletes (age, 6-15 years; n = 896) using a self-reported questionnaire. Multiple logistic regression models were used to assess the factors related to LBP along with the odds ratio (OR) and 95% confidence interval (95% CI). Variables included in the analysis were sex, age, body mass index, team level, number of days and hours of training, frequency of participation in games, practice intensity, and lower extremity pain. The prevalence of LBP was 6.9% in judo, 4.7% in kendo, and 2.9% in karate. Older age was significantly associated with LBP in judo (adjusted OR, 2.12 [95% CI, 1.24-3.61]), kendo (1.77 [1.27-2.47]), and karate (2.22 [1.14-4.33]). Lower extremity pain was significantly associated with LBP in judo (6.56 [1.57-27.34]) and kendo (21.66 [6.96-67.41]). Coaches should understand the characteristics of LBP in each martial art to develop strategies to prevent LBP among school-aged martial arts athletes.

Musculoskeletal pain is a major problem among survivors of natural disasters. Functional disabilities in older adults increase after disasters and can lead to musculoskeletal pain. However, the effects of poor physical function on musculoskeletal pain after natural disasters remain unclear. This study aimed to elucidate the association of poor physical function with new-onset musculoskeletal pain among older survivors after the Great East Japan Earthquake (GEJE). Survivors aged ≥ 65 years, 3 years after the GEJE, were assessed longitudinally for 1 year (n = 646). Musculoskeletal pain was assessed using a self-reported questionnaire, and new-onset musculoskeletal pain was defined as absence and presence of pain at 3 years and 4 years, respectively, after the disaster. Physical function at 3 years after the disaster was assessed using the Kihon Checklist physical function score, which consists of 5 yes/no questions, and poor physical function was defined as a score of ≥ 3/5. Multivariate logistic regression analyses were used to assess the association of poor physical function with new-onset musculoskeletal pain. The incidence of new-onset musculoskeletal pain was 22.4%. Participants with poor physical function had a significantly higher rate of new-onset musculoskeletal pain. Compared with high physical function, the adjusted odds ratio (95% confidence interval) for new-onset musculoskeletal pain was 2.25 (1.37-3.69) in poor physical function (P = 0.001). Preceding poor physical function was associated with new-onset musculoskeletal pain among older survivors after the GEJE. There is need to focus on the maintenance of physical function to prevent musculoskeletal pain after natural disasters.

Basketball is a major sport worldwide among different age groups that leads to a high frequency of injuries at multiple body sites. Upper and lower extremities and lower back are common pain sites in basketball players; however, there is little information about the relationship between upper or lower extremity pain and lower back pain. This study elucidated the associations between upper extremity (shoulder and elbow) pain and lower back pain (LBP) among young basketball players. We conducted a cross-sectional study using self-reported questionnaires mailed to 25,669 young athletes; the final study population comprised 590 basketball players, and their median age was 13 years (range: 6-15 years). The point prevalence rates of lower back, shoulder, elbow, and upper extremity pain among young basketball players were 12.9% (76/590), 4.6% (27/590), 2.7% (16/590), and 7.1% (42/590), respectively. Multivariate logistic regression analyses revealed that upper extremity pain was significantly associated with LBP (adjusted odds ratio [OR]: 7.86; 95% confidential interval [CI], 3.93-15.72). Shoulder pain was significantly associated with training per week (> 4 days) (adjusted OR: 4.15; 95% CI: 1.29-13.40) and LBP (adjusted OR: 13.77; 95% CI: 5.70-33.24). This study indicates that upper extremity and shoulder pain is associated with LBP among young basketball players. Assessing for lower back pain, as well as elbow and/or shoulder pain, may help prevent severe injuries in young basketball players. In conclusion, parents and coaches should be properly re-educated to help improve lower back, upper extremity, and shoulder pain among young basketball players.

Verbal or physical abuse from coaches has negative effects on young athletes, and the parents of athletes also have an influence on the sports environment. It is therefore important to understand parents' attitudes towards abuse against their children from the coaches. This study aimed to elucidate the characteristics of parents who accept the infliction of verbal or physical abuse on their children from coaches of youth sports teams. A cross-sectional study using self-report questionnaires was conducted with parents of young athletes (n = 6,493). Multivariate logistic regression models were used to assess the factors associated with parents' acceptability of verbal or physical abuse against their children. The proportion of parents who were accepting of verbal or physical abuse was 21.5%. Acceptability of verbal or physical abuse was significantly associated with male (odds ratio: 1.67, 95% confidence interval: 1.43-1.95), younger age (1.24, 1.09-1.41), lower educational attainment (1.32, 1.17-1.50), smoking habits (1.42, 1.23-1.63), experience of playing on a team with high levels of competition during their junior or high school days (1.31, 1.15-1.50), and experience of verbal and physical abuse by their own former coaches (3.59, 3.03-4.26 and 1.17, 1.02-1.35). About 58% and 28% of parents had experienced verbal and physical abuse from their own former coaches, and parents who had experienced verbal abuse themselves were most likely to be accepting of verbal or physical abuse towards their children. Educating parents is considered to be important for preventing and eradicating abuse against young athletes.

Verbal and physical abuse from coaches has negative effects on young athletes. Although the abuse can lead to the athletes' dropping out, no studies have reported on this topic. The purpose of this study was to elucidate the association between experience of verbal or physical abuse from coaches and loss of motivation for the present sport in young athletes. School-aged athletes (age range, 6-15 years, n = 6,791) were assessed using a self-reported questionnaire. Multivariate logistic regression models were used to assess the association between experience of verbal or physical abuse and loss of motivation for the present sport. Variables considered in the models were sex, age, body mass index, presence of bodily pain, team levels, number of training days per week, number of training hours per day on weekdays and weekends, and frequency of participation in games. The prevalence of loss of motivation for the present sport was 8.1%. Experience of verbal or physical abuse was significantly associated with loss of motivation for the present sport and the adjusted odds ratios (95% confidence intervals) were 1.93 (1.54-2.42, p < 0.001) for verbal abuse and 1.76 (1.27-2.42, p = 0.001) for physical abuse. Findings of this study suggest that experience of verbal or physical abuse from coaches is associated with loss of motivation for the present sport. Eradication of verbal and physical abuse from coaches is important for young athletes to continue sport participation.

Lower back pain (LBP) is a common health problem after natural disasters. Although some related factors have been reported, the effect of sleep disturbances on LBP is not clear. The purpose of this study was to elucidate the influence of sleep disturbances on LBP after the Great East Japan earthquake (GEJE). A panel study was conducted with the survivors of the GEJE (n = 2,295) at three and four years after the disaster using self-reported questionnaires. The changes in the presence of LBP during the two periods were assessed; LBP was characterized as either new onset or continuation of LBP. The participants' sleep conditions were assessed, and the changes in sleep disturbances during the two periods were classified into four groups: absence, new onset, improvement, and continuation. Multivariate logistic regression models were used to analyze the association of the changes in sleep disturbance with new onset and continuation of LBP. The rates of new onset and continuation of LBP were 14.1% and 55.1%, respectively. The changes in sleep disturbances were significantly associated with new-onset and continuing LBP. Using "absence" as a reference for the change of sleep disturbance, the adjusted ORs (95% CI) for new-onset LBP were 2.19 (1.42-3.38) in "new onset," 1.38 (0.83-2.30) in "improvement," and 2.17 (1.50-3.15) in "continuation," and those for continuing LBP were 1.42 (0.71-2.84) in "new onset," 0.98 (0.55-1.74) in "improvement," and 1.60 (1.01-2.51) in "continuation." Careful attention should be paid to sleep disturbances to prevent and improve LBP after natural disasters.

Verbal or physical abuse from coaches has a negative impact on young athletes. To prevent abuse against young athletes, it is important to know the characteristics of abusive coaches. This study aimed to elucidate the characteristics of coaches who commit verbal or physical abuse in youth sports teams. A cross-sectional study was conducted with coaches of youth sport teams in Miyagi prefecture, Japan (n = 1,283), using a self-reported questionnaire (response rate was 24.0%). Multivariate logistic regression models were used for analyses. The prevalence of verbal and physical abuse towards young athletes was 64.7% (n = 830) and 6.2% (n = 79), respectively. Verbal abuse was significantly associated with lower educational attainment (odds ratio (OR): 1.32, 95% confidence interval (95% CI): 1.03-1.69), experiences of verbal abuse by own coaches (OR: 1.85, 95% CI: 1.37-2.50), acceptability for verbal or physical abuse (OR: 2.53, 95% CI: 1.82-3.52), and dissatisfaction with athletes' attitude (OR: 1.62, 95% CI: 1.26-2.07). Physical abuse was significantly associated with experiences of physical abuse by respondents' coaches (OR: 2.71, 95% CI: 1.50-4.92), acceptability for verbal or physical abuse (OR: 3.89, 95% CI: 2.39-6.33), and longer experience of coaching in years (OR: 2.45, 95% CI: 1.20-4.98). The results of this study show that coaches who commit verbal or physical abuse had typically experienced abuse from their former coaches, and adopted a similar style. Breaking the negative cycle of verbal and physical abuse is necessary to eliminate the abuse of young athletes.

Rotator cuff tears (RCTs) are a common shoulder problem in the elderly that can lead to both muscle atrophy and fatty infiltration due to less physical load. Satellite cells, quiescent cells under the basal lamina of skeletal muscle fibers, play a major role in muscle regeneration. However, the myogenic potency of human satellite cells in muscles with fatty infiltration is unclear due to the difficulty in isolating from small samples, and the mechanism of the progression of fatty infiltration has not been elucidated. The purpose of this study was to analyze the population of myogenic and adipogenic cells in disused supraspinatus (SSP) and intact subscapularis (SSC) muscles of the RCTs from the same patients using fluorescence-activated cell sorting. The microstructure of the muscle with fatty infiltration was observed as a whole mount condition under multi-photon microscopy. Myogenic differentiation potential and gene expression were evaluated in satellite cells. The results showed that the SSP muscle with greater fatty infiltration surrounded by collagen fibers compared with the SSC muscle under multi-photon microscopy. A positive correlation was observed between the ratio of muscle volume to fat volume and the ratio of myogenic precursor to adipogenic precursor. Although no difference was observed in the myogenic potential between the two groups in cell culture, satellite cells in the disused SSP muscle showed higher intrinsic myogenic gene expression than those in the intact SSC muscle. Our results indicate that satellite cells from the disused SSP retain sufficient potential of muscle growth despite the fatty infiltration.

Sleep disturbance is a common symptom after natural disasters. Although musculoskeletal pain also increases after natural disasters, its relation to sleep disturbance is not clear. The purpose of this study was to determine the influence of musculoskeletal pain on new-onset sleep disturbance among survivors after the Great East Japan Earthquake (GEJE). A prospective cohort study was conducted with the survivors of the GEJE at two and three years after the earthquake. New-onset sleep disturbance was defined as sleep disturbance absent at two years and present at three years after the earthquake. The sites of musculoskeletal pain included low back, shoulder, knee, and hand or foot. The number of musculoskeletal pain sites at two years after the earthquake was divided into three categories (0, 1, and 2 or more). Univariate and multivariate logistic regression models were used to calculate the odds ratio (OR) and 95% confidence interval (95%CI) for new-onset sleep disturbance according to the number of musculoskeletal pain sites. A total of 1,102 survivors were included in this study and 14.6% of the participants reported new-onset sleep disturbance. Using "0" as a reference, the adjusted ORs (95% CI) for new-onset sleep disturbance were 2.43 (1.55-3.80) in "1" and 2.96 (1.88-4.64) in "2 or more", respectively (P for trends < 0.001). In conclusion, this is the first study showing higher incidence of sleep disturbance among survivors with musculoskeletal pain after the GEJE. Care for musculoskeletal pain is important to prevent sleep disturbance after natural disasters.

Elbow or shoulder injuries are common in overhead sports. Because energy derived from the lower extremity passes through the trunk to the upper extremity in overhead motion, a break in such a kinetic chain could lead to arm injuries. However, there is only limited information about the role of the trunk and lower extremity support in preventing elbow or shoulder injuries. This study aimed to explore the association of trunk and lower extremity pain with elbow/shoulder pain among young overhead athletes. We conducted a cross-sectional study using self-reported questionnaires mailed to young athletes belonging to the Miyagi Amateur Sports Association. The final study population comprised 2,215 young athletes playing baseball (n = 1,422), volleyball (n = 546), softball (n = 14), handball (n = 28), tennis (n = 110), or badminton (n = 95). The median age of the participants was 11 years (range: 6 to 15 years). Multiple logistic regression analysis revealed the higher prevalence of elbow and/or shoulder pain in athletes with back pain (OR = 5.52, 95% CI = 3.51-8.69), hip pain (OR = 6.13, 95% CI = 3.35-11.22), knee pain (OR = 2.28, 95% CI = 1.48-3.51), and foot pain (OR = 3.03, 95% CI = 1.95-4.72), compared with those without pain. We propose that trunk or lower extremity pain is significantly associated with elbow or shoulder pain among young overhead athletes. Assessing for pain in trunk or lower extremity, as well as elbow and/or shoulder pain, may help prevent serious injuries in young overhead athletes.

The Great East Japan Earthquake (GEJE) and Tsunami devastated the northeastern coast of Japan on March 11, 2011. This study attempted to determine whether socio-psychological factors such as sleep disturbance and psychological distress influenced new-onset subjective shoulder pain in survivors, during the post disaster phase of the GEJE. From November 2012 to February 2013 (2 years after the GEJE) and November 2014 to January 2015 (4 years after the GEJE), survivors (18 years old or over) answered self-reported questionnaires. In total, 1,454 survivors responded to the questionnaires and were thus included in this study. New-onset subjective shoulder pain was defined as shoulder pain by encircled response absent at 2 years, and present at 4 years after the GEJE. Two years after the GEJE, ≥ 10/24 points on the Kessler Psychological Distress Scale-6, and ≥ 6/24 points on the Athens Insomnia Scale defined the presence of psychological distress and sleep disturbance, respectively. Multiple logistic regression analysis was used to estimate the odds ratio (OR) and 95% confidence interval (CI) of the association between new-onset subjective shoulder pain, and psychological distress or sleep disturbance. Amongst participants, 7.2% (105/1,454) reported new-onset subjective shoulder pain. Sleep disturbance was significantly associated with new-onset subjective shoulder pain (OR = 1.92, 95% CI = 1.24-2.98, P = 0.004); however, psychological distress was not (OR = 0.78, 95% CI = 0.42-1.42, P = 0.41). In conclusion, this is the first study indicating an association between sleep disturbance and new-onset subjective shoulder pain amongst the survivors of the GEJE.

Dental problems among athletes have been cautioned due to negative impacts not only on their oral health but also on athletic performance. Acquirement of appropriate oral health behavior mainly composed of toothbrushing in childhood can be one of the most important strategies for advancing children's athletic possibilities. Although habits of screen viewing, including game playing, and TV viewing have direct impacts on children's health and behavioral development, little is known about the association between these habits and toothbrushing frequency. A cross-sectional survey examining sports activities was conducted using a self-report questionnaire among school-aged athletic children belonging to the Miyagi Amateur Sports Association (n = 6,658). All statistical analyses were performed with SPSS, and P-values less than 0.05 were considered statistically significant. The association between a lower brushing frequency (< 2 times a day) and screen-viewing behavior was examined using multivariate logistic models after adjusting for sex, age, body mass index (BMI), studying time, and sleep duration. After adjustment for all covariates, longer game playing (> 2 hrs a day), but not TV viewing, significantly correlated with lower brushing frequency (P for trend < 0.001). Importantly, longer game-playing behavior was also associated with unhealthy dental behavior defined as a lower brushing frequency regardless of the awareness of dental caries (P for trend < 0.001). In conclusion, this is the first study indicating a type-specific unfavorable impact of screen viewing on oral health behavior among athletic children. Excessive game playing may adversely affect oral health literacy more strongly than TV viewing.

In March 2011, the Great East Japan Earthquake (GEJE), which was followed by a devastating tsunami, destroyed the societal and the public hygiene systems in Japanese coastal areas. Insomnia, the greatest issue among disaster victims, has detrimental effects on both physical and psychological health. Periodontitis causes chronic discomfort and inflammation, and little is known about its impact on insomnia. Three months after the earthquake, a health panel survey was conducted over four surveys, till September 2013, in which information regarding 8,015 adults was collected and used. In addition to the heath-related questionnaire, other variables including subjective symptoms of oral diseases were recorded, and the Athens Insomnia Scale was used to evaluate the severity of insomnia. The association between insomnia and periodontal disease was examined using multilevel logistic models on the panel data, after adjusting for sex, age, economic status, comorbidities, body mass index, post-traumatic stress reactions, habitual smoking and alcohol drinking, and the Kessler Psychological Distress Scale score. In addition to the higher prevalence of insomnia among GEJE victims, significant association was revealed between insomnia and gum problems (OR = 2.16, 95% CI = 1.43-3.26), and difficulty chewing (OR = 2.22, 95% CI = 1.40-3.51), after adjusting for all covariates. The present study revealed significant association between insomnia and periodontal disease among GEJE victims. This indicated that together, integrated oral health care for disaster victims would contribute not only to prevention of oral infectious diseases, but may also help alleviate other problems caused by these harmful events.

Joint immobilization, which is used in orthopaedic treatments and observed in bedridden people, usually causes restricted joint motion. Decreased joint motion diminishes activities of daily living and increases burden of nursing-care. The purpose of this study was to clarify the reversibility of immobilization-induced capsular changes and restricted joint motion in rat knee joints. The unilateral knee joints of adult male rats were immobilized with an internal fixator for 1, 2, 4, 8, and 16 weeks as a model of immobilization after surgery or disuse of the joint. After the fixation devices were removed, the rats were allowed to move freely for 16 weeks. Sham-operated rats were used as controls. Sagittal sections at medial midcondylar regions were made and assessed with histological, histomorphometric, and immunohistochemical methods. Joint motion was measured using a custom-made device under x-ray control after removal of the periarticular muscles. In the 1/16-week and 2/16-week immobilization-remobilization (Im-Rm) groups, cord-like structures connecting the superior and inferior portions of the posterior capsule (partial adhesion) were observed without restricted joint motion. In the 4/16-, 8/16-, and 16/16-week Im-Rm groups, global adhesion of the posterior capsule and restricted joint motion were observed. The restricted joint motion was not completely restored after incision of the posterior capsule. These data indicate that immobilization alone causes irreversible capsular changes and arthrogenic restricted joint motion. Besides the joint capsule, other arthrogenic factors such as ligaments might influence the restricted joint motion. Prolonged immobilization over 4 weeks should be avoided to prevent irreversible joint contracture.

Joint immobilization is commonly used for the treatment of joint injuries, but it causes articular cartilage degeneration. The purpose of this study was to clarify the reversibility of immobilization-induced articular cartilage degeneration using rat knee joints. Immobilization of rat knee joints induces atrophic changes in the non-contact area, loss of chondrocytes in the contact area, and hypertrophy of chondrocytes in the transitional area of the articular cartilage. The unilateral knee joints of adult male rats were rigidly immobilized at 150° of flexion with a plate and screws for 1, 2, and 4 weeks. After the experimental periods, the fixation devices were removed and the rats moved freely for 16 weeks. Sham-operated rats were used as a control. Sagittal sections at medial midcondylar regions of the knee were assessed with histological and histomorphometric methods. Mechanical properties were assessed by measuring the sound speed with scanning acoustic microscope. Reduction of cartilage proteoglycan in the non-contact area was almost reversible, but hypertrophy of chondrocytes in the transitional area and loss of chondrocytes in the contact area were irreversible even at 1-week immobilization-remobilization group. Sound speed of the articular cartilage in the contact area was not restored. These results indicate that atrophic changes through decreased mechanical stress in the non-contact area were reversible, but loss of chondrocytes and hypertrophy of chondrocytes in the contact and transitional areas through increased mechanical stress by rigid immobilization were irreversible after remobilization. Clinicians should be aware that even a short-term rigid immobilization could cause irreversible articular cartilage damage.

Joint immobilization is commonly used for the treatment of joint injuries and diseases, but it also causes unfavorable outcomes such as joint contracture. The purpose of this study was to examine the morphological changes of the synovial membrane that is suspected as a cause of joint contracture, and localization of type A (macrophage-like) and type B (fibroblast-like) synoviocytes in the capsule after joint immobilization. Male Sprague-Dawley rats were used in this study. Unilateral knee joints were rigidly immobilized at 150 degrees of flexion with internal fixators for 3 days, 1, 2, 4, 8, and 16 weeks (7 rats/each immobilized group), while 42 rats were sham-operated. Sagittal sections of 5 mum were prepared from the medial midcondylar region of the knee joints and assessed with histological, histomorphometric, and immunohistochemical methods. Adhesions were observed both in the anterior and posterior synovial membranes in the immobilized group after 2 weeks. In the adhesion area, the cells were mainly composed of type A synoviocytes that were positive for CD68 and type B synoviocytes positive for prolyl 4-hydroxylase subunit beta. The length of synovial membrane in the immobilized group was significantly shorter than that in the control group after 2 and 4 weeks. After 8 weeks, the adhesion area in the immobilized group became fibrous and hypocellular. The staining intensity of hyaluronic acid-binding protein was increased after 16 weeks. Adhesion and shortening of the synovial membrane and the structural changes of the adhesion area may contribute to the development of joint contracture.

Joint immobilization is commonly used for the treatment of joint injuries and diseases, but it also causes cartilage degeneration. Damage to the fibrillar meshwork of type II collagen in the articular cartilage is a critical event for cartilage degeneration. Collagenases such as matrix metalloproteinase (MMP)-8 and MMP-13 have been considered the main enzymes responsible for the degradation of type II collagen. However, the mechanism of the articular cartilage degeneration after immobilization has not been revealed. The purpose of this study was to examine changes of the expression patterns of MMP-8 and MMP-13 after rigid immobilization of the knee joint. The unilateral knee joints of adult male rats were rigidly immobilized at 150 degrees of flexion using an internal fixator. Histological sections from the medial midcondylar region of the knee were obtained and evaluated in 3 specific areas (non-contact, transitional, and contact areas). The expression of MMP-8 and MMP-13 was evaluated by in situ hybridization. Total RNA was extracted from the articular cartilage in the contact area, and expression levels of MMP-8 and MMP-13 mRNAs were measured by quantitative real-time polymerase chain reaction. Localization of MMP-13 expression was also examined by immunohistochemistry. The expression of MMP-8 mRNA was decreased by 1 week after immobilization. After 4-week immobilization, hypertrophic differentiated chondrocytes were observed in the transitional and contact areas, and the expression of MMP-8 and MMP-13 mRNAs was increased in the chondrocytes. Rigid immobilization is associated with the increased expression of MMP-8 and MMP-13 in the hypertrophic differentiated chondrocytes. These two collagenases may play an important role in the articular cartilage degeneration after joint immobilization.

Joint immobilization is a useful and common treatment modality in orthopedics. However, it also causes unfavorable outcome such as articular cartilage degeneration. Intra-articular injection of hyaluronan has been accepted as a treatment of osteoarthritis, but its effects on immobilized joint remain to be clarified. Hyaluronan is a polysaccharide, distributed ubiquitously in various tissues. In this study, we examined the effect of hyaluronan on the articular cartilage in immobilized joints. The unilateral knee joints of adult male rats were immobilized at 150 degrees in flexion with an internal plate and screws for 1, 2, 4, 6, 8, 12, or 16 weeks (n = 84). Hyaluronan or saline (50 microl/each injection) was administered intra-articularly on the day of surgery and once a week. The articular cartilage from the medial midcondylar region of the knee was obtained, and divided into non-contact, contact and transitional areas (between the non-contact and the contact areas). In each area, a degree of degeneration was evaluated by histomorphometric grading, and measurements of thickness and number of chondrocytes. Histological grading scores in the hyaluronan group were smaller at 12 and 16 weeks compared with those in the saline group. The thickness of the articular cartilage increased in the transitional area in both groups. The number of chondrocytes in the contact and transitional areas gradually decreased, but their number in the hyaluronan group was greater at 12 and 16 weeks compared with that in the saline group. Hyaluronan showed chondroprotective effects on the articular cartilage in a rat immobilized-knee model.

Focal fibrocartilaginous dysplasia (FFCD) is a rare and benign bone lesion that induces bowing deformity of the long bones in young children. Excessive production of fibrocartilage by abnormal differentiation in the metaphysis or by trauma during delivery or after birth is thought to cause growth disturbance. Radiologically, the lesion is characterized by a lucent defect with marginal sclerosis in the medial metaphysis of the long bone. However, there have been few reports about the initial radiological changes of FFCD before bowing started. We report a patient with FFCD in the left distal femur in whom the radiological changes were serially observed during the course of the disorder. A 2-week-old boy first visited our hospital because of left thigh pain. Plain radiographs did not show any abnormal findings at that time. At 10 weeks, a well-defined lucent defect with bony fragment inside was observed in the distal femoral medial cortex. At 1 year, this bony fragment gradually vanished but varus deformity progressed and reached approximately 40 degrees at the age of 2. After removal of the lesion, osteotomy and immobilization was performed with Ilizarov external fixator comprising rings, rods and wires. Complete bone union was achieved 3 months after operation. It is noteworthy that we could observe the initial radiological changes of FFCD before varus deformity occurred. As far as we know, there have been no descriptions of the bony fragment inside a lucent defect of the lesion. Radiological features may vary in the early phase of FFCD.