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The Japanese Orthopaedic Association (JOA) introduced the concept of locomotive syndrome (LS), which indicates a decline in mobility function by musculoskeletal disorders with new 3-staged category. Additionally, sarcopenia indicates a decline in the quantity and/or quality of skeletal muscle. However, the relationship between low back pain (LBP) and LS or sarcopenia in older people has not been sufficiently understood. This study aimed to investigate the association between them through a cross-sectional locomotorium survey.A total of 302 participants were drawn from the aquatic exercise participants in a rural area of Japan. The body mass index, body fat percentage, skeletal muscle mass index (SMI), spinal inclination angle (SIA), grip strength, timed up-and-go test (TUG), and maximum stride of the participants were measured. LBP and LBP-related quality of life (QOL) were evaluated using the Oswestry Disability Index (ODI), visual analogue scale (VAS) of LBP, and the Short-Form 8 (SF-8). Associations between the investigating parameters and sarcopenia or LS were analyzed.There were no significant differences in the findings except grip strength between the non-sarcopenia and sarcopenia groups. However, the LS group showed significantly larger SIA, higher ODI, higher VAS of LBP, lower physical component score (PCS) of the SF-8, longer time in TUG, and lower value in maximum stride than the non-LS group. In addition, the ODI and PCS of the SF-8 significantly deteriorated as the LS stage progressed, and the GLFS-25 score was significantly correlated with ODI (r = 0.706, p 0.001) and PCS (r = -0.643, p 0.001) scores.LBP, LBP-related QOL, and physical performance were found to be significantly associated with LS, not sarcopenia, with LBP-related QOL and physical function being closely correlated with 3-stage categories of LS. Thus, these results suggested that LBP is a key factor for LS prevalence.

Background Adult spinal deformity has a substantially debilitating effect on older people’s physical and mental health. However, the impact of sagittal malalignment on locomotive syndrome (LS), sarcopenia, and physical function in community-dwelling older women has not yet been clarified. This study aimed to investigate the association between these factors in community-dwelling older women. Methods A total of 361 women were recruited from participants performing aquatic exercises in a rural area of Japan. The body mass index, skeletal muscle mass index, trunk muscle mass, spinal inclination angle (SIA), grip strength, timed up-and-go test (TUG), maximum stride of the participants, and one-leg standing time were measured. Low back pain (LBP)- and health-related quality of life (HRQOL) were evaluated using the Oswestry Disability Index (ODI) and the Short-Form 8 questionnaire. Associations between the global sagittal alignment using SIA and investigating parameters were analyzed. Results The prevalence of sarcopenia was 16.6%. The prevalence of LS (stages 1, 2, and 3) was 43.8% (158 of 361), and the number of participants in each LS stage was 203 (stage 0), 95 (stage 1), 28 (stage 2), and 35 (stage 3). The SIA was significantly correlated with the 25-question geriatric locomotive function scale (r′= 0.292, p r′= 0.267, p r′= 0.453, p

Purpose: Macrophage accumulation in response to decreasing myonuclei may be the major mechanism underlying immobilization-induced muscle fibrosis in muscle contracture, an intervention strategy suppressing these lesions is necessary. Therefore, this research investigated the effect of belt electrode-skeletal muscle electrical stimulation (B-SES), a new electrical stimulation device, to the macrophage accumulation via myonuclei decrease in immobilization-induced muscle fibrosis. Materials and methods: 18 Wistar male rats were divided into the control group, immobilization group (with plaster cast fixation to immobilize the soleus muscles in a shortened position for 2 weeks), and B-SES group (with muscle contractile exercise through B-SES during the immobilization period). B-SES stimulation was performed at a frequency of 50 Hz and an intensity of 4.7 mA, muscle contractile exercise by B-SES was applied to the lower limb muscles for 20 minutes/session (twice a day) for 2 weeks (6 times/week). The bilateral soleus muscles were used for histological, immunohistochemical, biochemical, and molecular biological analyses. Results: The number of myonuclei was significantly higher in the B-SES group than in the immobilization group, and there was no significant difference between the B-SES and control groups. The cross-sectional area of type I and II myofibers in the immobilization and B-SES groups was significantly lower than that in the control group, and the cross-sectional area of type I myofibers in the B-SES group was higher than that in the immobilization group. However, Atrogin-1 and MuRF-1 mRNA expression in the immobilization and B-SES groups was significantly higher than those in the control group. Additionally, the number of macrophages, IL-1β, TGF-β1, and α-SMA mRNA expression, and hydroxyproline expression was significantly lower in the control and B-SES groups than those in the immobilization group. Conclusion: This research surmised that muscle contractile exercise through B-SES prevented immobilization-induced muscle fibrosis, and this alteration suppressed the development of muscle contracture., PLoS ONE, 16(5), art. no. e0244120; 2021

Severe acute pain after total knee arthroplasty (TKA) may cause delay in muscle strength and functional recovery, and it is a risk factor for chronic postoperative pain. Although pharmacological approaches are the typical firstline to treat acute pain; recently, nonpharmacological approaches such as exercise have been increasingly applied. The purpose of this investigation was to evaluate the effects of a rehabilitation program involving isometric quadriceps exercise with auditory and visual feedback to improve the short-term outcome after TKA. Sixty-two patients, planning a primary unilateral TKA, were randomly assigned to either an intervention group (n = 31) involving isometric quadriceps exercise with auditory and visual feedback in usual rehabilitation after TKA or a control group (n = 31) involving a standardized program for TKA. Patients in the intervention group performed the isometric quadriceps muscle exercise using the Quadriceps Training Machine from 2 to 14 days after TKA instead of the traditional quadriceps sets. Pain intensity, isometric knee extension strength, range of motion, timed up and go test (TUG), 10-m gait speed, 6-minute walking distance, the Western Ontario and McMaster University Osteoarthritis index (WOMAC), the hospital anxiety and depression scale, and the pain catastrophizing scale were assessed before TKA (baseline) and 1 to 3 weeks after TKA. Pain intensity significantly decreased in the intervention group than in the control group at 1 (p = 0.005), 2 (p = 0.002), and 3 (p = 0.010) weeks after TKA. Greater improvements in TUG (p = 0.036), 10-m gait speed (p = 0.047), WOMAC total score (p = 0.017), pain (p = 0.010), and function (p = 0.028) 3 weeks after TKA were observed in the intervention group. These results suggest that isometric quadriceps exercises with auditory and visual feedback provided early knee pain relief, possibly leading to better improvements in physical performance, and patient's perception of physical function in the early stages of postoperative TKA. Further studies should investigate whether this short-term effect is sustainable.

Abtsract Background Identifying indicators of early knee osteoarthritis is important for preventing the onset and/or progression of the disease. Although low quadriceps strength and changes in stride and knee kinematics during gait have been suggested as possible indicators, their relevance and relationships have not been fully examined. This study aimed to analyze the association of quadriceps strength with stride and knee kinematics during gait in adults with normal knee or early knee osteoarthritis. Methods A total of 881 knees from 474 community dwelling adults (238 males and 236 females) were included. Radiographic images of the knee in standing position were obtained, and grading of knee osteoarthritis was classified. Isometric quadriceps strength was measured using a force detector device. Three-dimensional knee kinematics during gait was obtained by a motion capture system. Sex-based difference of quadriceps strength, stride and knee kinematics during gait was evaluated by multiple comparison among grades by sex and multiple regression of quadriceps strength was analyzed by stride and knee kinematics during gait. Findings Stride length and quadriceps strength were significantly reduced with higher grade in both sexes, and changes in knee kinematics during gait differed by sex from early knee osteoarthritis. Quadriceps strength in both sexes was significantly correlated with changes in stride length and knee kinematics during gait. Interpretation Improving quadriceps strength in early knee osteoarthritis was related with maintaining gait ability and restraining abnormal knee kinematics during gait. This may help to develop clinical approaches to prevent the onset and/or progression of knee osteoarthritis.

Background Quadriceps muscle strength reference value of normal individuals in Japan is necessary to quantitatively evaluate functional deterioration of locomotive organs. Therefore, we established a reference value by using the Locomo Scan, a new device that measures knee extension muscle strength. Methods We measured knee extension muscle strength with the Locomo Scan in 3617 individuals (1692 men, 1925 women, 20–89 years; mean age. 50.7 years) by implementing our own 49 measurement events in 20 prefectures. Results The means of maximum knee extension muscle strength for men (women) in each age group were as follows: 20s, 546 (475) N; 30s. 552 (475) N; 40s, 534 (450) N; 50s, 507 (442) N; 60s, 471 (405) N; 70s, 385 (340) N; and 80s, 359 (267) N. No significant differences were found from the 20s to 40s age groups, but older groups had significantly decreased knee extension muscle strength with age for both sexes. Conclusions We established reference values for quadriceps muscle strength with the Locomo Scan as an index for functional deterioration of locomotive organs based on a large-scale sample.

The purpose of this study was to investigate the causal relationship between quadriceps muscle strength and radiographic knee osteoarthritis (OA) in a longitudinal study. The present study included 976 knees from 488 subjects who participated in both the 5th (2007) and 7th (2013) surveys of the Matsudai Knee Osteoarthritis Survey. Bilateral quadriceps strengths of each subject were measured using the quadriceps training machine (QTM-05F, Alcare Co., Ltd., Tokyo, Japan). Additionally, weight-bearing standing knee radiographs were obtained, and knee OA was graded according to the Kellgren–Lawrence classification system. The relationships between quadriceps strength and the incidence and progression of radiographic knee OA were assessed using multiple logistic regression analysis. After adjusting for age and body mass index (BMI), both female and male knees in the lowest quantile of quadriceps strength had higher risk of the incidence of radiographic knee OA compared with the highest quantile of quadriceps strength (women: OR 2.414, 95% CI 1.098–5.311; men: OR 2.774, 95% CI 1.053–7.309). In contrast, after adjusting for age, BMI and femorotibial angle, both female and male knees in the lowest quantile compared with the highest quantile of quadriceps strength did not differ in risk of the progression of radiographic knee OA (women: OR 1.040, 95% CI 0.386–2.802; men: OR 2.814, 95% CI 0.532–14.898). Quadriceps muscle weakness was related to increased risk of the incidence of radiographic knee OA, but not its progression, in both women and men. Therefore, the clinically important finding of this study is that, in both women and men, maintaining higher quadriceps muscle strength may be one of the most effective prevention methods for incident radiographic knee OA. II.

Objectives To comprehensively investigate the clinical and physical factors associating with locomotive syndrome (Loc-S); the locomotorium-disability for daily life. Methods 647 volunteers participated (247 males, 400 females, Age: 58.4 ± 11.0, BMI: 22.5 ± 3.3). Three self-assessment questionnaires were administered: 1) “25-question Geriatric Locomotive Function Scale” (GFLS-25) for evaluating Loc-S (GLFS-25 ≥ 16 defined as Loc-S); 2) “diagnostic support tool for LSS” (LSS-DST) for evaluating the prevalence of lumbar spinal stenosis (LSS); 3) Knee injury and Osteoarthritis Outcome Score (KOOS). Plain radiographs of the bilateral knees and lumbar spine were evaluated, and the severity of lumbar spondylosis (LS) and knee osteoarthritis (KOA) defined by Kellgren–Lawrence grade. Bone status was evaluated by using the osteo-sono assessment index (OSI) at the calcaneus. Isometric muscle strength of trunk and leg (Nm/kg, both extension and flexion) were evaluated. Linear regression analysis was performed to elucidate the factors concerned with GFLS-25 including age, sex, and BMI. Results Thirty-nine subjects (6.0%, 13 males, 26 females) were defined as having Loc-S. Single regression model showed that age, height, BMI, skeletal muscle mass, OSI, LSS, KOOS, the severity of LS and KOA, and trunk- and leg-muscle strength were correlated with the degree of GLFS-25. Stepwise multiple regression model showed that sex, height, LSS, KOOS, the severity of LS, and back muscle strength were significantly correlated with that of GLFS-25. Conclusion In this cross-sectional study, pain status associated with LSS and knee joint, structural severity for LS, and back muscle strength primarily affected the degree of GFLS-25. For managing Loc-S, we must pay more intensive attention to these factors.

Knee osteoarthritis (OA) is a multifactorial disease and strongly affected by mechanical factors. The aims of the present study were to assess validity and reliability of a new muscle strength measuring device, the Quadriceps Training Machine (QTM) and evaluate the relationship between quadriceps strength measured by QTM and radiographic knee OA by epidemiological survey.The isometric knee extension muscle strength of QTM was compared with BIODEX in 24 healthy adults. Then, the relationship between radiographic knee OA and quadriceps strength using QTM was investigated with 2,032 knees in 1,016 subjects by an epidemiological survey (Matsudai Knee Osteoarthritis Survey).Significant correlation was observed between QTM and BIODEX (r = 0.69, 0.82). In the Matsudai Knee Osteoarthritis Survey, the prevalence of radiographic OA (grade II or higher upon Kellgren-Lawrence classification) was: 13, 36.9, 67.8, and 86.5 %, regarding women in their fifties, sixties, seventies, and eighties, respectively, and was 1.7, 13.4, 33.5, and 66.2 % regarding men, respectively. Quadriceps muscle strength declined following 50 years of age, and significant decline was observed in the their sixties and seventies. Quadriceps muscle strength of the OA group (grades II, III and IV) was significantly declined compared with that of the Non-OA group (grade-0 and I). Furthermore, the tendency of the muscle strength level to decline with the progression of knee OA grade was particularly observed between grade 0 and grade I in both men and women and between grade I and grade II in men.The relationship between radiographic knee OA and quadriceps strength was quantitatively evaluated by an epidemiological survey, and we found a correlation between knee OA and the decline in quadriceps strength. Furthermore, it was suggested that the decline in quadriceps muscle strength may be more strongly related to the incidence of knee OA than to its progression.

Background Knee osteoarthritis (OA) is a multifactorial disease that is affected by mechanical factors. The aim of present study was to investigate the association between multiple mechanical factors and medial knee OA in a large epidemiological cohort. Methods Six hundred and ninety-nine subjects (323 males and 376 females), participating in the Matsudai Knee Osteoarthritis Survey 2010, were included. Twelve mechanical factors were selected and their association with the radiographic grade of knee OA, the Western Ontario and McMaster University Index (WOMAC) pain score, and the WOMAC function score was evaluated. Results A logistic regression analysis identified varus thrust to be associated with the radiographic grade of knee OA in males (OR: 1.876, 95% CI: 1.332–2.663) and females (2.61, 1.922–3.542), the WOMAC pain score in males (1.997, 1.463–2.672), and the WOMAC function score in females (1.449, 1.12–1.874). Quadriceps muscle strength was associated with the radiographic OA grade in males (0.605, 0.399–0.917) and females (0.636, 0.469–0.863), the WOMAC pain score in females (0.537, 0.445–0.789), and the WOMAC function score in males (0.581, 0.44–0.766). The knee flexion angle was also associated with the radiographic OA grade in males (0.344, 0.19–0.621) and females (0.121, 0.022–0.653), and the WOMAC pain score in males (0.287, 0.156–0.53) and females (0.537, 0.336–0.859). Obesity was associated with the radiographic OA grade in males (1.543, 1.041–2.287) and females (1.589, 1.176–2.146), the WOMAC pain score in female (2.017, 1.517–2.68). Femolo-tibial angle had no significant association with the radiographic knee OA grade or with the WOMAC pain and function scores. Conclusion Among patients with medial knee OA, dynamic mechanical factors, such as varus thrust, quadriceps muscle strength, and range of motion were more likely to be associated with the radiographic grade of knee OA and to be the WOMAC pain and function scores, compared to static mechanical factors.

In diagnosis and treatment of knee joint diseases, it is effective to study the three-dimensional (3D) motion of the patient's knee joint involving the femur, tibia, and patella. A 2D/3D registration method with use of fluoroscopy and CT images is promising for this purpose. However, there is no report showing whether the dynamic 3D motion of the patella can be obtained. In this study, we tried to examine dynamic 3D motion of the knee joint which included the patella. First, in order to investigate the accuracy of the position estimation, we conducted an experiment on a pig knee joint which had several fiducial markers placed on it, and we found that errors in the estimation of rotation and translation were less than 1 mm and 1 deg. We then carried out an image-acquisition experiment with healthy knee joints of three volunteers and confirmed that 3D motions of the femur, tibia, and patella were successfully obtained for all cases.

Trunk muscle weakness and imbalance are risk factors for postural instability, low back pain, and poor postoperative outcomes. The association between trunk muscle strength and aging is poorly understood, and establishing normal reference values is difficult. We aimed to establish the validity of a novel portable trunk muscle torque measurement instrument (PTMI). We then estimated reference data for healthy young adults and elucidated age-related weakness in trunk muscle strength. Twenty-four university students were enrolled to validate values for PTMI, and 816 volunteers from the general population who were recruited to the Iwaki Health Promotion Project were included to estimate reference data for trunk muscle strength. Trunk flexion and extension torque were measured with PTMI and KinCom, and interclass correlation coefficients (ICC) were estimated to evaluate the reliability of PTMI values. Furthermore, from the young adult reference, the age-related reduction in trunk muscle torque and the prevalence of sarcopenia among age-sex groups were estimated. The ICC in flexion and extension torque were 0.807 (p

Spinal orthoses are implemented to restrict lumbar motion. Several studies have compared the effectiveness of various types of lumbar orthoses on restricting motion, but none have compared the effect of different back supports on restricting extension. This study sought to evaluate the effectiveness of three types of lumbar orthosis in regard to their ability to restrict motion during extension. Range of motion was quantified using the Spinal Mouse system to measure flexion and extension, and the load distribution of the back support was measured using a pressure sensor. Ten subjects (8 men, 2 women) were assessed under the following five experimental conditions: custom-made stay (CMS), aluminum stay (AS), plastic stay (PS), corset only, and no brace. None of the stays changed the flexion angle, and none of the supports prevented flexion bending. The mean extension angle after immobilization with the CMS, AS, PS, corset only, and no brace was 27.5° ± 8.5°, 33.4° ± 11.0°, 34.3° ± 9.4°, 37.8° ± 10.7°, and 42.6° ± 10.5°, respectively. The load in the CMS was concentrated at the vertical ends of the stay, with a mean load of 11.5 ± 2.4 N at the top and 8.9 ± 2.4 N at the bottom. The loads at the top and bottom of the support were 7.2 ± 4.3 and 5.3 ± 3.1 N with the AS and 5.8 ± 2.3 and 4.4 ± 1.7 N with the PS, respectively. All supports allowed similar flexion motion. Although the CMS, AS, and PS all restricted extension compared with no brace, the CMS was the most effective for restricting trunk extension motion.

Previously, we proposed a 2D/3D registration method that uses Powell’s algorithm to obtain 3D motion of a knee joint by 3D computed-tomography and bi-plane fluoroscopic images. The 2D/3D registration is performed consecutively and automatically for each frame of the fluoroscopic images. This method starts from the optimum parameters of the previous frame for each frame except for the first one, and it searches for the next set of optimum parameters using Powell’s algorithm. However, if the flexion motion of the knee joint is fast, it is likely that Powell’s algorithm will provide a mismatch because the initial parameters are far from the correct ones. In this study, we applied a hybrid optimization algorithm (HPS) combining Powell’s algorithm with the Nelder–Mead simplex (NM-simplex) algorithm to overcome this problem. The performance of the HPS was compared with the separate performances of Powell’s algorithm and the NM-simplex algorithm, the Quasi-Newton algorithm and hybrid optimization algorithm with the Quasi-Newton and NM-simplex algorithms with five patient data sets in terms of the root-mean-square error (RMSE), target registration error (TRE), success rate, and processing time. The RMSE, TRE, and the success rate of the HPS were better than those of the other optimization algorithms, and the processing time was similar to that of Powell’s algorithm alone.

s / Osteoarthritis and Cartilage 21 (2013) S63–S312 S168 differences. Second, it can be used to explore the effects of various ‘what if’ scenarios that can demonstrate system wide and long-term effects that may result from changes in care processes. For example, two scenarios examined were: “What would happen if 1) primary care providers could manage more patients medically, ultimately referring fewer patients to specialists; and 2) primary care providers in all health zones adopted one zone's rheumatologist referral patterns for OA patients?” Such scenarios change the pathways through which simulated patients flow, the results of which can provide insight into intended and unintended effects on resource use and costs across the continuum of care over a lengthy time horizon. Conclusions: Our SD model can be used as a decision-support tool to estimate changes in health care demands, resource requirements and costs over time and as a result of ‘what if’ scenarios. It is critically important to involve clinicians and decision-makers in the development of such tools to ensure they are appropriate representations of the system and to facilitate their adoption and continued use to inform decision making. 319 QUADRICEPS MUSCLE STRENGTH AND ITS RELATIONSHIP TO RADIOGRAPHIC KNEE OSTEOARTHRITIS G. Omori y, Y. Koga z, H. Watanabe x, A. Nawata k, K. Narumi k, K. Endoh {. yCtr. for Transdisciplinary Res., Niigata Univ., Niigata City, Japan; zOrthopaedic Surgery, Niigata Med. Ctr., Niigata City, Japan; xRehabilitation Unit, Niigata Med. Ctr., Niigata City, Japan; kMed. Engineering Lab., Alcare Co. Ltd, Tokyo, Japan; {Niigaat Univ. of Hlth. and Welfare, Niigata City, Japan Purpose: Knee osteoarthritis (knee OA) is multifactorial disease and strongly affected by mechanical factors. The aims of the present study were to develop a lightweight muscle strength measuring device and investigate the relationship between knee OA and quadriceps muscle strength by epidemiological survey. Methods: We developed portable quadriceps muscle training machine (QTM) and the accuracy of measuring was evaluated. Then, the relationship between radiographic knee OA and quantitative quadriceps muscle strength was investigated by epidemiological survey (Matsudai Knee Osteoarthritis Survey) using this device. Results: Significant correlation was observed between QTM and BIODEX (r1⁄40.69, 0.82). In Matsudai Knee Osteoarthritis Survey, 2032 knees in 1016 subjects (482 men and 534 women), average age was 65.9 13.0 years old, were investigated. The prevalence of radiographic OA (grade II or higher upon Kellgren-Lawrence classification) was: 13%, 36.9%, 67.8%, and 86.5%, regardingwomen in their fifties, sixties, seventies, and eighties, respectively, and was 1.7%, 13.4%, 33.5%, and 66.2% regarding men, respectively. Quadriceps muscle strength declined following 50 years of age, and significant decline was observed in their sixties and seventies. Quadriceps muscle strength of OA group (grades II, III and IV) was significantly declined comparing with that of Non-OA group (grade-0 and I). Furthermore, tendency of the muscle strength level to decline with the progression of knee OA grade was particularly observed between grade 0 and grade I in both men and women and between grade I and grade II in men. Conclusions: This is the first report in Japan that quantitatively evaluated the relationship between knee OA and quadriceps muscle strength in epidemiological survey, and we found the correlation between knee OA and the decline in quadriceps muscle strength. Furthermore, it suggests that the decline in quadriceps muscle strength may be more strongly related to the incidence of knee OA than its progression. 320 ALTERED CARTILAGE PHENOTYPE IN MICE LACKING SIRT 1 GENE O.H. Gabay, Jr. y, K.J. Zaal, Jr. y, C. Sanchez, Jr. z, M. Dvir-Ginzberg, Jr. x, V. Gagarina, Jr. y, Y. Song, Jr. k, X. He, Jr. {, M. McBurney, Sr. {. yNIH, Bethesda, MD, USA; zBCRU Univ. of Liege, Liege, Belgium; xHebrew Univ. HaddassahEin Kerem, Jerusalem, Israel; kUniformed Services Univ. of The Hlth.Sci., Bethesda, MD, USA; {Ottawa Hosp. Res. Inst., Ottawa, ON, Canada Purpose: Degenerative diseases of the cartilage, such as osteoarthritis, are age-related. The histone deacetylase Sirt 1 (silent information regulator 2 homolog 1) is thought to be an anti-aging protein. We previously demonstrated that Sirt 1 regulates apoptosis and cartilagespecific gene expression in human chondrocytes. To determine if Sirt 1 plays a protective role in cartilage homeostasis in vivo, we investigated Sirt 1 KO and Sirt 1mutant mice to characterize their cartilage and try to understand the mechanisms underlying a phenotype, such as cartilage breakdown or apoptosis. Method: Articular cartilage was harvested from hind paws and knees of 1-week to 6-month-old mice carrying wild type, null, or point mutations affecting the Sirt 1 gene. The cartilage was processed for histology and immunohistochemistry or used to establish cultures of chondrocytes. Results: We found that articular cartilage tissue sections from Sirt1 KO mice and mutant mice, at any age, exhibited low levels of type 2 collagen, aggrecan, and glycosaminoglycans. In contrast, protein levels of MMP-8, MMP-9, and MMP-13 were elevated in the Sirt1 KO and mutant mice, leading to an increase of cartilage breakdown. The apoptotic process was shown to be elevated in these mice. Moreover, PTP1b (protein tyrosine phosphatase b)_a chondrocyte proapoptotic protein elevated in OA_was elevated in the Sirt1 KO mice. Conclusion: The findings from these animal models demonstrated that Sirt1 KOmice andmice expressing a mutant allele of Sirt 1 presented an altered cartilage phenotype. The apoptotic process and the cartilage breakdown were elevated in these mice. 321 NOVEL CANDIDATE GENES FOR STRUCTURAL FOOT DISORDERS: A GENOME-WIDE ASSOCIATION STUDY IN AN OLDER CAUCASIAN POPULATION M.T. Hannan y, C.-H. Cheng z, Y. Liu x, J.M. Jordan x, Y.-H. Hsu y. yHebrew SeniorLife & Harvard Med. Sch., Roslindale, MA, USA; zHebrew SeniorLife, Roslindale, MA, USA; xUniv. of North Carolina, Chapel Hill