Genetics of osteoarthritis

Finding the Goldilocks Zone of Mechanical Loading: A Comprehensive Review of Mechanical Loading in the Prevention and Treatment of Knee Osteoarthritis

In this review, we discuss the interaction of mechanical factors influencing knee osteoarthritis (KOA) and post-traumatic osteoarthritis (PTOA) pathogenesis. Emphasizing the importance of mechanotransduction within inflammatory responses, we discuss its capacity for being utilized and harnessed within the context of prevention and rehabilitation of osteoarthritis (OA). Additionally, we introduce a discussion on the Goldilocks zone, which describes the necessity of maintaining a balance of adequate, but not excessive mechanical loading to maintain proper knee joint health. Expanding beyond these, we synthesize findings from current literature that explore the biomechanical loading of various rehabilitation exercises, in hopes of aiding future recommendations for physicians managing KOA and PTOA and athletic training staff strategically planning athlete loads to mitigate the risk of joint injury. The integration of these concepts provides a multifactorial analysis of the contributing factors of KOA and PTOA, in order to spur further research and illuminate the potential of utilizing the body's own physiological responses to mechanical stimuli in the management of OA.

The Role of Nutrition in Osteoarthritis Development

Osteoarthritis (OA) prevalence has increased 113% since 1990, and currently more than half a billion people worldwide are living with this slowly progressing, degenerative joint disease [...].

Demographic and radiographic factors for knee symptoms and range of motion in patients with knee osteoarthritis: a cross-sectional study in Beijing, China

BACKGROUND

Knee osteoarthritis (KOA) causes not only pain, stiffness, and dysfunction of the knee, but also the reduction of the joint range of motion (ROM). This study explored the demographic and radiographic factors for knee symptoms and ROM in patients with symptomatic KOA.

METHODS

The demographic variables, Kellgren-Lawrence (KL) grade, and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) of patients with symptomatic KOA recruited in Beijing were collected. The knee ROM of all patients were also measured. We analyzed the influencing factors for WOMAC and ROM using a generalize linear model, respectively.

RESULTS

This study included a total of 2034 patients with symptomatic KOA, including 530 males (26.1%) and 1504 females (73.0%), with a mean age of 59.17 (± 10.22) years. Patients with advanced age, overweight or obesity, a family history of KOA, a moderate-to-heavy manual labor job and use of nonsteroidal anti-inflammatory drugs (NSAIDs) had significantly higher WOMAC and lower ROM (all P < 0.05). The more the comorbidities, the higher the WOMAC (all P < 0.05). Patients with higher education had better ROM than those with only an elementary education(β = 4.905, P < 0.05). Compared with those KL = 0/1, the WOMAC of patients whose KL = 4 were higher (β = 0.069, P < 0.05), but the WOMAC of those KL = 2 were lower (β = -0.068, P < 0.05). ROM decreased with the increase of KL grade (all P < 0.05).

CONCLUSIONS

KOA patients with advanced age, overweight or obesity, a family history of KOA in first-degree relatives, a moderate-to-heavy manual labor job tended to have more severe clinical symptoms and worse ROM. Patients with more severe imaging lesions tend to have poorer ROM. Symptom management measures and regular ROM screening should be taken early to these people.

Factors Associated with Kinesiophobia in Patients with Knee Osteoarthritis

Purpose This study aims to determine factors affecting kinesiophobia in patients with knee osteoarthritis (OA).

Materials and Methods The fear of movement was measured using the Tampa Scale of Kinesiophobia in 60 patients with knee OA. Pain intensity was assessed with the Visual Analog Scale, quality of life with the Nottingham Health Profile (NHP), disability with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), anxiety and depression with the Hospital Anxiety and Depression Scale (HADS), balance with the Berg Balance Scale, mobility with the Timed Up and Go Test, and the physical activity status was measured with the International Physical Activity Questionnaire.

Results Physical mobility and emotional reactions subscales of NHP, all WOMAC subscales and the HADS depression subscale were significantly related to kinesiophobia. Muscle strength, ROM, level of physical activity, balance, mobility and anxiety were not significantly related to kinesiophobia. Quality of life and disability explained 34.4% of the variation in the Tampa Scale of Kinesiophobia.

Conclusions Kinesiophobia was associated with quality of life, disability and depression. It may be useful for clinicians to pay attention to the evaluation of psychosocial characteristics instead of physical performance parameters in order to increase treatment success in OA patients.

Erosive hand osteoarthritis: latest findings and outlook

Osteoarthritis (OA) most commonly affects knee joints, and the next most commonly affected sites are the hands and hips. Three distinct hand OA phenotypes have been described: erosive hand OA (EHOA), nodal hand OA - also known as non-erosive hand OA (non-EHOA) - and first carpometacarpal joint OA. EHOA predominantly affects women and is the most aggressive form of hand OA, characterized by a severe clinical onset and progression, leading to joint damage, disability and reduction of quality of life. Clinical signs of inflammation associated with EHOA include the acute onset of pain, swelling and redness. Moreover, EHOA is characterized by radiographic features such as central erosion, saw-tooth and gull-wing lesions and, rarely, ankylosis. The aim of this Review is to report the latest findings on epidemiology, clinical features, pathology and aetiopathogenesis, biomarkers, imaging modalities and treatments for EHOA. The ongoing development of new hand OA classification criteria should facilitate standardization between studies.

Pathogenesis of Osteoarthritis: Risk Factors, Regulatory Pathways in Chondrocytes, and Experimental Models

As the most common chronic degenerative joint disease, osteoarthritis (OA) is the leading cause of pain and physical disability, affecting millions of people worldwide. Mainly characterized by articular cartilage degradation, osteophyte formation, subchondral bone remodeling, and synovial inflammation, OA is a heterogeneous disease that impacts all component tissues of the articular joint organ. Pathological changes, and thus symptoms, vary from person to person, underscoring the critical need of personalized therapies. However, there has only been limited progress towards the prevention and treatment of OA, and there are no approved effective disease-modifying osteoarthritis drugs (DMOADs). Conventional treatments, including non-steroidal anti-inflammatory drugs (NSAIDs) and physical therapy, are still the major remedies to manage the symptoms until the need for total joint replacement. In this review, we provide an update of the known OA risk factors and relevant mechanisms of action. In addition, given that the lack of biologically relevant models to recapitulate human OA pathogenesis represents one of the major roadblocks in developing DMOADs, we discuss current in vivo and in vitro experimental OA models, with special emphasis on recent development and application potential of human cell-derived microphysiological tissue chip platforms.

The effectiveness of foot orthoses in the treatment of medial knee osteoarthritis: A systematic review

BACKGROUND

Knee osteoarthritis is a disease of the joint causing decreased function and pain. Currently, treatments range from medication to surgery, with the use of different insoles and footwear recommended. These methods are effective by either correcting the position of the knee or providing shock absorption. However, there is little understanding of the effective characteristics of these devices.

RESEARCH QUESTION

This paper aims to investigate this question and provide future areas of research to help better define treatment guidelines. Foot orthoses are an example of non-pharmacological conservative treatments mentioned in National Institute for Health and Care Excellence (NICE) guidelines to treat knee osteoarthritis (OA). These include lateral wedge insoles (LWI), developed with the intention of load reduction of the knee. Different footwear has also been shown to affect pain, biomechanical and functional outcomes in knee OA patients.

METHODS

To address what features of LWIs and footwear make them effective in the treatment of knee OA, scientific databases were used to search for papers on this topic and then selected to be included based on pre-defined criteria. Data were extracted and analysed from these studies to provide a basis for possible areas for future development of these foot orthoses, and research required to improve clinical treatment guidelines. Databases used were PubMed, Scopus and Web of Science.

RESULTS AND SIGNIFICANCE

Thirty-four out of 226 papers were included after application of inclusion and exclusion criteria. Regarding LWIs, the characteristics showing the most beneficial effect on either biomechanical, functional or pain outcomes were customisation, full-length, 5° elevation, shock absorption and arch support. For footwear, barefoot mimicking soles produced the most favourable biomechanics. Results also showed that insoles work in correcting the position of the knee, but it may or may not affect patients' pain and function.

The effects of two different water exercise trainings on pain, functional status and balance in patients with knee osteoarthritis

METHODS

Eighty-nine female patients who had been diagnosed with knee osteoarthritis were divided into three groups as two experimental and a control group. All groups have received the standard therapy (hotpack, ultrasound, TENS). Both experimental groups underwent water exercise program. While Group 1 performed lower extremity exercise training, Group 2 performed upper extremity exercises as well as trunk exercises in addition to the lower extremity exercises used in the Group 1. The third group was control group who did not receive water exercise treatment. The pain severity was measured with the Visual Analog Scale (VAS). Functional status was assessed by using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Balance was evaluated by using the single leg stance test.

RESULTS

The change in VAS scores from pre-to post-treatment was highest in Group 1 (p < 0.001). On the other hand, the change in WOMAC pain, stiffness and physical function values from pre-to post-treatment was highest in Group 2 (p < 0.001).

DISCUSSION

Water exercise training was found to be beneficial in the treatment of knee osteoarthritis in both groups. Moreover, adding upper extremity and trunk exercises to the lower extremity exercises was found to be more effective for improving the function.

Clinical Management in Early OA

Knee osteoarthritis affects an important percentage of the population throughout their life. Several factors seem to be related to the development of knee osteoarthritis including genetic predisposition, gender, age, meniscal deficiency, lower limb malalignments, joint instability, cartilage defects, and increasing sports participation. The latter has contributed to a higher prevalence of early onset of knee osteoarthritis at younger ages with this active population demanding more consistent and durable outcomes. The diagnosis is complex and the common signs and symptoms are often cloaked at these early stages. Classification systems have been developed and are based on the presence of knee pain and radiographic findings coupled with magnetic resonance or arthroscopic evidence of early joint degeneration. Nonsurgical treatment is often the first-line option and is mainly based on daily life adaptations, weight loss, and exercise, with pharmacological agents having only a symptomatic role. Surgical treatment shows positive results in relieving the joint symptomatology, increasing the knee function and delaying the development to further degenerative stages. Biologic therapies are an emerging field showing early promising results; however, further high-level research is required.

Integrated bioinformatics analysis of the osteoarthritis‑associated microRNA expression signature

Numerous studies have focused on osteoarthritis (OA) cartilage injuries, with observations of abnormalities in microRNA (miRNA) expression levels. The aim of the present study was to consolidate and assess the results of these studies to identify potential miRNA biomarkers of OA. A comprehensive meta‑analysis of eight independent miRNA expression studies in OA was performed using the robust rank aggregation method (RRA), which contained a total of 82 OA and 39 normal cartilage samples. The targets of meta‑signature miRNA were predicted using TargetScan v6.2, PicTar, miRDB, TarBase v7.0 and starBase databases. In addition, pathway enrichment analysis was performed to establish the biologically and functionally relevant genes involved in meta‑signature miRNA regulation. Six dysregulated miRNAs were identified, including four up regulated (miR‑23b‑3p, miR‑27b‑3p, miR‑211‑5p and miR‑16‑5p) and two down regulated (miR‑25‑3p and miR‑149‑5p). The enrichment of Kyoto Encyclopedia of Genes and Genomes and Panther signaling pathways were predominantly associated with cell signaling and cell regulation. In the present study, the meta‑signature miRNA identified may be used to develop a series of diagnostic and prognostic biomarkers for OA specifically for use in a clinical setting.

Associations between vitamin D receptor gene polymorphisms and osteoarthritis: an updated meta-analysis

OBJECTIVE

Vitamin D receptor (VDR) gene polymorphisms may be associated with the risk of OA, however, evidence for this is controversial. This meta-analysis aims to confirm whether VDR gene polymorphisms are associated with OA.

METHODS

Meta-analyses on the association between OA and VDR ApaI, BsmI, TaqI and FokI polymorphisms were conducted using allele and homozygote contrast and contrasts in the recessive and dominant models. Stratification analyses by different demographic regions (Europe vs Asian) were also performed and pooled odds ratios (ORs) were obtained using the random effects model if the results were heterogeneous.

RESULTS

A total of 13 relevant studies involving OA patients (n = 2104) and controls (n = 2939) were included in the analysis. There were significant associations between VDR ApaI polymorphisms and OA in the Asian population (A vs a: OR= 1.16, 95% CI 1.02, 1.32, P = 0.025; AA vs Aa/aa: OR= 1.36, 95% CI 1.04, 1.77, P = 0.025; AA vs aa: OR= 1.35, 95% CI 1.00, 1.80, P = 0.047), but not in the whole population. There was also a statistically significant association between FokI polymorphism and OA (FF vs Ff/ff: OR= 0.65, 95% CI 0.44, 0.95, P = 0.024); however, this result was derived from only two studies. No significant associations were found between VDR TaqI and BsmI polymorphisms and OA.

CONCLUSION

There are modest but statistically significant associations between VDR ApaI polymorphisms and the susceptibility of OA in the Asian population.

TBS result is not affected by lumbar spine osteoarthritis

The effect of lumbar osteoarthritis on bone density and trabecular bone score (TBS) was evaluated cross-sectionally and prospectively in postmenopausal women. Lumbar spine osteoarthritis was graded according to Kellgren and Lawrence grades. Lumbar osteoarthritis was found to increase lumbar spine bone density, but not TBS.

INTRODUCTION

Lumbar osteoarthritis overestimates lumbar bone density (areal bone mineral density (aBMD)). A new texture parameter, the TBS, has been proposed. Calculation of aBMD uses grey level value, while TBS uses grey level variation. Therefore, our hypothesis was that TBS is not influenced by lumbar spine osteoarthritis.

METHODS

Menopausal women participating in osteoporosis and ultrasound (OPUS) study were included. They had an aBMD measurement of the spine and hip at baseline and 6-year visit. TBS was calculated on lumbar spine dual-energy X-ray absorptiometry (DXA) scans in an automated manner. The presence of lumbar osteoarthritis was evaluated on baseline radiographs using Kellgren and Lawrence (K&L) classification. Grades range from 0 to 4. In our study, osteoarthritis was defined by at least K&L grade 2.

RESULTS

This study included 1,254 menopausal women (66.7 ± 7.1 years). Among them, 727 attended the 6-year follow-up visit. Patients with lumbar osteoarthritis had an aBMD higher than those without lumbar osteoarthritis at the lumbar spine, but not at the hip. However, the aBMD significantly increased in all sites with the grade of K&L. In contrast, spine TBS was not different between patients with and without lumbar osteoarthritis (p = 0.70), and it was not correlated with K&L grade. Spine TBS and aBMD at all sites were negatively correlated with age (p < 0.0001). Body mass index was correlated positively with aBMD and negatively with spine TBS (p < 0.0001). The 6-year change of aBMD was significant in the hip and nonsignificant in the lumbar spine. That of TBS was significant, with a 3.3 % decrease (p < 0.0001), independent of K&L grade (p = 0.28).

CONCLUSION

In postmenopausal women, lumbar osteoarthritis leads to an increase in lumbar spine aBMD. In contrast, spine TBS is not affected by lumbar osteoarthritis.

Genetic influences on hand osteoarthritis in Finnish women--a replication study of candidate genes

Objectives

Our aims were to replicate some previously reported associations of single nucleotide polymorphisms (SNPs) in five genes (A2BP1, COG5, GDF5, HFE, ESR1) with hand osteoarthritis (OA), and to examine whether genes (BCAP29, DIO2, DUS4L, DVWA, HLA, PTGS2, PARD3B, TGFB1 and TRIB1) associated with OA at other joint sites were associated with hand OA among Finnish women.

Design

We examined the bilateral hand radiographs of 542 occupationally active Finnish female dentists and teachers aged 45 to 63 and classified them according to the presence of OA by using reference images. Data regarding finger joint pain and other risk factors were collected using a questionnaire. We defined two hand OA phenotypes: radiographic OA in at least three joints (ROA) and symptomatic DIP OA. The genotypes were determined by PCR-based methods. In statistical analysis, we used SNPStats software, the chi-square test and logistic regression.

Results

Of the SNPs, rs716508 in A2BP1 was associated with ROA (OR = 0.7, 95% CI 0.5–0.9) and rs1800470 in TGFB1 with symptomatic DIP OA (1.8, 1.2–2.9). We found an interaction between ESR1 (rs9340799) and occupation: teachers with the minor allele were at an increased risk of symptomatic DIP OA (2.8, 1.3–6.5). We saw no association among the dentists. We also found that the carriage of the COG5 rs3757713 C allele increased the risk of ROA only among women with the BCAP29 rs10953541 CC genotype (2.6; 1.1–6.1). There was also a suggestive interaction between the HFE rs179945 and the ESR1 rs9340799, and the carriage of the minor allele of either of these SNPs was associated with an increased risk of symptomatic DIP OA (2.1, 1.3–2.5).

Conclusions

Our results support the earlier findings of A2BP1 and TBGF1 being OA susceptibility genes and provide evidence of a possible gene-gene interaction in the genetic influence on hand OA predisposition.

Cartilage tissue engineering: molecular control of chondrocyte differentiation for proper cartilage matrix reconstruction

BACKGROUND

Articular cartilage defects are a veritable therapeutic problem because therapeutic options are very scarce. Due to the poor self-regeneration capacity of cartilage, minor cartilage defects often lead to osteoarthritis. Several surgical strategies have been developed to repair damaged cartilage. Autologous chondrocyte implantation (ACI) gives encouraging results, but this cell-based therapy involves a step of chondrocyte expansion in a monolayer, which results in the loss in the differentiated phenotype. Thus, despite improvement in the quality of life for patients, reconstructed cartilage is in fact fibrocartilage. Successful ACI, according to the particular physiology of chondrocytes in vitro, requires active and phenotypically stabilized chondrocytes.

SCOPE OF REVIEW

This review describes the unique physiology of cartilage, with the factors involved in its formation, stabilization and degradation. Then, we focus on some of the most recent advances in cell therapy and tissue engineering that open up interesting perspectives for maintaining or obtaining the chondrogenic character of cells in order to treat cartilage lesions.

MAJOR CONCLUSIONS

Current research involves the use of chondrocytes or progenitor stem cells, associated with "smart" biomaterials and growth factors. Other influential factors, such as cell sources, oxygen pressure and mechanical strain are considered, as are recent developments in gene therapy to control the chondrocyte differentiation/dedifferentiation process.

GENERAL SIGNIFICANCE

This review provides new information on the mechanisms regulating the state of differentiation of chondrocytes and the chondrogenesis of mesenchymal stem cells that will lead to the development of new restorative cell therapy approaches in humans. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Vitamin D receptor gene polymorphisms and risk of osteoarthritis: A meta-analysis

The vitamin D receptor (VDR) gene polymorphisms have been reported to be involved in the development of many musculoskeletal disorders, including osteoarthritis (OA). However, results were inconsistent and there is no definite conclusion regarding the association between any VDR polymorphism and the risk of OA. In this study, we conducted a meta-analysis to determine whether BsmI, TaqI, and ApaI polymorphisms in the VDR gene are associated with OA susceptibility. Literature research was performed using PubMed and EMBASE databases. Studies illustrating the association between the three VDR polymorphisms and OA were included, and their qualities were assessed using Newcastle–Ottawa scale. Eight eligible studies, recruiting 1626 cases and 2024 controls were identified. Their methodological qualities were generally good, with scores ranging from 6 to 8 points. However, throughout all summary analyses, which were performed for multiple categories and on four contrasts (allele contrast, contrast of homozygotes, recessive and dominant models), none of the VDR BsmI, TaqI, and ApaI gene polymorphisms were found to be significantly associated with the risk of OA. On the other hand, there was no significant publication bias. Results from this meta-analysis suggested that the VDR BsmI, TaqI, and ApaI gene polymorphisms might not be important predictors of OA. More studies further investigating these associations, especially taking into account of gene–gene, gene–environment interactions, and other confounding factors are warranted.

Joint and bone assessment in hand osteoarthritis

Hand osteoarthritis (OA) is a common disease frequently affecting middle-aged women. Prevalence estimates for OA vary widely depending on the age and sex of the population studied, the assessment tools used, and the specific joint sites analyzed OA is characterized by the degradation of articular cartilage, subchondral bone changes and osteophyte formation at the joint margins leading to joint failure. The pathogenesis of the disease and its evolution are multifactorial involving biomechanical, metabolic, hormonal, and genetic factors. Moreover, the role of inflammation has recently been advanced as pivotal in OA onset and progression. In particular, an uncommon variant of hand OA, erosive hand OA, is characterized by inflammatory and degenerative interphalangeal proximal and distal joints. The diagnosis of different types of hand OA is centered on clinical and laboratory investigations which can distinguish the peculiar aspects of these forms. Joint and bone assessments in hand OA are widely studied but there is no agreement with regard to established parameters to make a definitive diagnosis. This report focuses on the laboratory and clinimetric assessments that can be used to distinguish hand OA subtypes and addresses the debatable association with low bone mineral density in osteoporosis.

Degenerative changes of the temporomandibular joint. Relationship to ethnicity, sex and occlusal supporting zones based on a skull material

OBJECTIVE

The first aim of this study was to examine a contemporary human skull material for possible ethnic differences in respect of degenerative changes in the temporomandibular joints (TMJs). A second aim was to see if there was any correlation between such changes and occlusal support in any of the two groups and, if so, if this correlation was sex-related.

MATERIALS AND METHODS

The material consisted of 129 Caucasian skulls and 76 skulls from Afro-Americans. Ninety-four of the Caucasian skulls came from males (73%) and the corresponding figure for the Afro-Americans was 40 (53%). Their mean age at death was 46 years (range: 19-89 years) and 37 years (range: 18-70 years), respectively.

RESULTS

Dental status was in general poor and 13% of the Afro-Americans and 26% of the Caucasians were edentulous. Form and surface changes of the TMJs were more common in the present material compared to most previous studies. No differences could be found between the two ethnic groups in respect of degenerative joint changes in the TMJs. In men, no correlation of clinical relevance could be found between severity of joint changes and occlusal support. However, in both Caucasian and Afro-American women, such a correlation was obvious, especially in higher age.

CONCLUSIONS

The present findings give no evidence for any differences in the prevalence of degenerative changes in the TMJs in Caucasians and Afro-Americans. The strong correlation found between such changes and occlusal support in women but not in men might be explained by hormonal differences.

Etiology of osteoarthritis: genetics and synovial joint development

Osteoarthritis (OA) has a considerable hereditary component and is considered to be a polygenic disease. Data derived from genetic analyses and genome-wide screening of individuals with this disease have revealed a surprising trend: genes associated with OA tend to be related to the process of synovial joint development. Mutations in these genes might directly cause OA. In addition, they could also determine the age at which OA becomes apparent, the joint sites involved, the severity of the disease and how rapidly it progresses. In this Review, I propose that genetic mutations associated with OA can be placed on a continuum. Early-onset OA is caused by mutations in matrix molecules often associated with chondrodysplasias, whereas less destructive structural abnormalities or mutations confer increased susceptibility to injury or malalignment that can result in middle-age onset. Finally, mutations in molecules that regulate subtle aspects of joint development and structure lead to late-onset OA. In this Review, I discuss the genetics of OA in general, but focus on the potential effect of genetic mutations associated with OA on joint structure, the role of joint structure in the development of OA--using hip abnormalities as a model--and how understanding the etiology of the disease could influence treatment.

Effects of Glucosamine and Chondroitin Sulfate on Cartilage Metabolism in OA: Outlook on Other Nutrient Partners Especially Omega-3 Fatty Acids

Osteoarthritis (OA) is a degenerative joint disease that is characterized by increasing loss of cartilage, remodeling of the periarticular bone, and inflammation of the synovial membrane. Besides the common OA therapy with nonsteroidal anti-inflammatory drugs (NSAIDs), the treatment with chondroprotectives, such as glucosamine sulfate, chondroitin sulfate, hyaluronic acid, collagen hydrolysate, or nutrients, such as antioxidants and omega-3 fatty acids is a promising therapeutic approach. Numerous clinical studies have demonstrated that the targeted administration of selected micronutrients leads to a more effective reduction of OA symptoms, with less adverse events. Their chondroprotective action can be explained by a dual mechanism: (1) as basic components of cartilage and synovial fluid, they stimulate the anabolic process of the cartilage metabolism; (2) their anti-inflammatory action can delay many inflammation-induced catabolic processes in the cartilage. These two mechanisms are able to slow the progression of cartilage destruction and may help to regenerate the joint structure, leading to reduced pain and increased mobility of the affected joint.

Risk factors for radiographic tibiofemoral knee osteoarthritis: the wuchuan osteoarthritis study

Objective. To investigate the risk factors of radiographic tibiafemoral knee osteoarthritis (OA). Methods. A population-based cross-sectional survey was conducted in Wuchuan County. A questionnaire and bilateral weight-bearing posterior-anterior semi-flexed knee radiographs were completed and read for Kellgren and Lawrence (K/L) grade and joint space narrowing (JSN; 0-3 scale) in each compartment. An logistic regression analysis was performed for radiographic tibiafemoral, lateral compartment, and medial compartment knee OA, respectively. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated. Results. Age, sex, and knee injury were strongly associated with tibiafemoral, lateral and medial compartment knee OA. BMI also had a dose-response relationship with them. Physical activity level, and physical activity exposure at work, not significantly though, were associated with an elevated risk for this three kinds of knee OA. Conclusions. Physical activity exposure increased the risk of knee OA. It was likely to be the heavier physical activity in Wuchuan osteoarthritis study that counteracted the BMI gap compared with the Beijing and the Framingham OA study. We verified that Chinese had a more valgus alignment of the knee compared with Caucasian population, and this provide a possible explanation why Chinese have a higher prevalence of lateral compartment OA.

Degenerative changes in human temporomandibular joints in relation to occlusal support

OBJECTIVE

Controversy exists concerning the etiological factors behind degenerative changes in the temporomandibular joints (TMJs). Tooth attrition, occlusal support, food consistency, ageing, gender and genetics are some possible causative factors that have been discussed in the literature. The aim of this study was to examine contemporary human skull material for possible relations between degenerative form and surface changes in the TMJs in relation to occlusal support.

MATERIAL AND METHODS

The material consisted of 259 human skulls from 170 males and 89 females, with an age range of 18-100 years.

RESULTS

Dental status was in general poor, and 22% of skulls were edentulous. Form and surface changes of both the condyles and the temporal components were more common in the present material compared to that in most previous studies. In males, irrespective of age, only weak and clinically insignificant correlations could be found between degenerative TMJ changes and occlusal support. In women, however, the correlations between these variables were in general much stronger, especially at higher ages.

CONCLUSIONS

The present findings do not lend support to the hypothesis that loss of occlusal support is a causative factor for degenerative changes in the TMJs in male subjects. In women, such a correlation was obvious in the present sample, at least at higher ages. It can be speculated that hormonal factors play a role in the sex difference found.

Genetics in osteoarthritis

Osteoarthritis is a degenerative articular disease with complex pathogeny because diverse factors interact causing a process of deterioration of the cartilage. Despite the multifactorial nature of this pathology, from the 50's it s known that certain forms of osteoarthritis are related to a strong genetic component. The genetic bases of this disease do not follow the typical patterns of mendelian inheritance and probably they are related to alterations in multiple genes. The identification of a high number of candidate genes to confer susceptibility to the development of the osteoarthritis shows the complex nature of this disease. At the moment, the genetic mechanisms of this disease are not known, however, which seems clear is that expression levels of several genes are altered, and that the inheritance will become a substantial factor in future considerations of diagnosis and treatment of the osteoarthritis.

[Genetics in osteoarthritis]

Osteoarthritis is a degenerative articular pathology with complex pathogeny because diverse factors interact causing a process of deterioration of the cartilage. In spite of the multifactorial nature of this pathology, from years 50 one knows that certain forms of osteoarthritis are related to a strong genetic component. The genetic bases of this disease do not follow the typical patterns of mendelian inheritance and probably they are related to alterations in multiple genes. The identification of a high number of candidates genes to confer susceptibility to the development of the osteoarthritis shows the complex nature of this disease. At the moment, the genetic mechanisms of this pathology are not known, however, which seems clear is that levels of expression of several genes are altered, and that the inheritance will become a substantial factor in future considerations of diagnosis and treatment of the osteoarthitis.

The role of sequence variations within the genes encoding collagen II, IX and XI in non-syndromic, early-onset osteoarthritis

OBJECTIVE

We sought to determine whether sequence variations in cartilage collagen genes are associated with primary, early-onset osteoarthritis (OA).

METHODS

The cartilage collagen genes, COL2A1, COL9A1, COL9A2, COL9A3, COL11A1 and COL11A2, were screened for sequence variations in 72 Finnish probands and one US family with primary early-onset hip and/or knee OA. In addition, allelic association studies were performed using six to 12 common polymorphisms from each gene by genotyping 72 OA patients and 103 controls.

RESULTS

Altogether 239 sequence variations were found, of which 16 were not present in the controls. Seven of the unique variations, four in COL11A1, two in COL11A2 and one in COL2A1, were studied further, because they resulted in the substitution of conserved amino acids or were predicted to affect mRNA splicing. Co-segregation of a sequence variation and the phenotype was found in all four families available for study. Association analysis failed to identify any common predisposing alleles.

CONCLUSIONS

Early-onset OA demonstrates locus and allelic heterogeneity since the identified variations were in three different collagen genes and each of the six probands had a different mutation. It is also possible that some OA cases represent the mild end of the chondrodysplasia phenotypic spectrum. The major susceptibility alleles in this form of OA, however, remain to be identified.

Hip dysplasia and osteoarthrosis: a survey of 4151 subjects from the Osteoarthrosis Substudy of the Copenhagen City Heart Study

INTRODUCTION

Hip dysplasia (HD) is assumed to be an etiological factor in the development of premature hip osteoarthrosis (OA). We established the prevalences of HD and OA in adults according to qualified radiographic discriminators, and investigated the relationship between HD and OA.

METHODS

Wiberg's CE angle (CE), Sharp's angle, the femoral head extrusion index, the acetabular depth ratio (ADR), the radiographic OA discriminators of Croft, and of Kellgren and Lawrence, and also minimum joint space width (JSW) < or = 2 mm were applied to the standing, standardized pelvic radiographs of 1429 men (22-93 years), and 2430 women (22-92 years).

RESULTS

The 4 HD discriminators were interrelated. A negligible sex-related difference in acetabular morphology was found, male acetabulae being slightly more dysplastic than female acetabulae. However, differences between the sexes for right and left CE angles were within 1.0 degree, and within 1.4 degrees for right and left Sharp's angles. There were no cases of hip subluxation (breakage of Shenton's line > or = 5 mm). Average CE angle was 34 degrees in men (SD 7.3 degrees), and 35 degrees in women (SD 7.6 degrees). Applying a CE cut-off value of 20 degrees for designation of definite hip dysplasia, we found a prevalence of hip dysplasia of 3.4%. Approximately 2% of cases were unilateral and 1.4% of cases were bilateral. We found significant relationships between radiographic OA discriminators and the CE angle, femoral head extrusion index and ADR. Odds ratios ranged from 1.0 to 6.2. Compared to subjects with OA in morphologically normal hips, a trend towards younger age in subjects with HD and OA was noted, but this was not strictly significant.

INTERPRETATION

We found that HD is not uncommon in the general population. The assumption that HD is an etiological factor in the development of hip OA was confirmed.

Reviewing knee osteoarthritis--a biomechanical perspective

Osteoarthritis (OA) is the most common form of arthritis and is a major cause of disability in people aged over 65. Despite the major socioeconomic burden imposed by OA, the aetiology of this condition remains unclear. Although controversial, several metabolic factors have been implicated in the disease pathogenesis. Nevertheless, no unequivocal systemic risk factors for the onset or progression of OA have been identified. Recently, there has been a growing interest in the biomechanical factors associated with the pathogenesis of OA. This review aims to discuss several of the more pertinent biomechanical and neuromuscular factors, such as the knee adduction moment and muscle strength, that are becoming increasingly accepted as factors that contribute toward the pathogenesis of knee OA.

Weight changes and the risk of knee osteoarthritis requiring arthroplasty

OBJECTIVE

To examine the effect of weight changes between 20 and 50 years of age on the risk of severe knee osteoarthritis (OA) requiring arthroplasty.

SUBJECTS AND METHODS

Cases were 55-75 year old men and women (n = 220) having had knee arthroplasty for primary osteoarthritis at the Kuopio University Hospital in 1992-93. Controls (n = 415) were randomly selected from the population of Kuopio Province. Weight at the age of 20, 30, 40, and 50 years was collected retrospectively with a postal questionnaire.

RESULTS

After adjustment for age, sex, history of physical workload, recreational physical activity, and previous knee injury, weight gain resulting to a shift from normal body mass index (BMI < or =25 kg/m(2)) to overweight (BMI >25 kg/m(2)) was associated with a higher relative risk of knee OA requiring arthroplasty than persistent overweight from 20-50 years of age, compared with those with normal relative weight during the corresponding age period. The odds ratios (OR) were 3.07 (95% confidence interval 1.87 to 5.05) for those with normal weight at the age of 20 years and overweight at two or three of the ages 30, 40 or 50 years, 3.15 (1.85 to 5.36) for those with overweight from the age of 30 years, and 2.37 (1.21 to 4.62) for those with overweight from the age of 20 years, respectively.

CONCLUSION

In adult life, a shift from normal to overweight may carry a higher risk for knee OA requiring arthroplasty than does constant overweight.

Risk factors for osteoarthritis: genetics

Although the multifactorial nature of osteoarthritis (OA) is well recognized, genetic factors have been found to be strong determinants of the disease. Evidence of a genetic influence of OA comes from a number of sources, including epidemiological studies of family history and family clustering, twin studies, and exploration of rare genetic disorders. Classic twin studies have shown that the influence of genetic factors is between 39% and 65% in radiographic OA of the hand and knee in women, about 60% in OA of the hip, and about 70% in OA of the spine. Taken together, these estimates suggest a heritability of OA of 50% or more, indicating that half the variation in susceptibility to disease in the population is explained by genetic factors. Studies have implicated linkages to OA on chromosomes 2q, 9q, 11q, and 16p, among others. Genes implicated in association studies include VDR, AGC1, IGF-1, ER alpha, TGF beta, CRTM (cartilage matrix protein), CRTL (cartilage link protein), and collagen II, IX, and XI. Genes may operate differently in the two sexes, at different body sites, and on different disease features within body sites. OA is a complex disease, and understanding its complexity should help us find the genes and new pathways and drug targets.

Quantitative assessment of cartilage status in osteoarthritis by quantitative magnetic resonance imaging: Technical validation for use in analysis of cartilage volume and further morphologic parameters

OBJECTIVE

Quantitative diagnostic tools for osteoarthritis (OA) are important for evaluating the treatment response to structure-modifying drugs. This study was undertaken to test the technical validity (accuracy) of quantitative magnetic resonance imaging (qMRI) for reliable determination of the total bone interface area, percentage of cartilaginous (denuded) joint surface area, and cartilage thickness in OA.

METHODS

High-resolution MRIs of femorotibial and patellar cartilage were acquired in 21 patients prior to total knee arthroplasty, using a T1-weighted gradient-echo sequence with water excitation. After segmentation of original bone interface areas (before disease onset) and the actual cartilage layer, the percentages of cartilaginous joint surface area, cartilage thickness, and cartilage volume were determined using proprietary software. During surgery, the patella and the medial and lateral tibia were resected. Results obtained with qMRI were compared with those obtained by direct image analysis of surface area, cartilage thickness, and cartilage volume of the surgically removed tissue.

RESULTS

Pairwise differences between results obtained with qMRI and morphologic analysis were +/-4.6% for percentage of cartilaginous surface area, +/-8.9% for cartilage thickness, and +/-9.1% for cartilage volume. Correlation coefficients ranged from 0.92 (thickness) to 0.98 (volume).

CONCLUSION

Quantitative MRI permits technically accurate and differential assessment of increases in eroded joint surface area and reductions in cartilage thickness in OA. The surrogate validity of these parameters requires testing in longitudinal studies. These parameters may be advantageous over determination of cartilage volume alone when diagnosing OA, exploring its progression, or testing responsiveness to new therapies.

Association study of candidate genes for the prevalence and progression of knee osteoarthritis

OBJECTIVE

Osteoarthritis (OA), characterized by late-onset degeneration of articular cartilage, is recognized to have a genetic component. We examined the role of 26 single-nucleotide polymorphisms (SNPs) from 24 candidate genes in OA susceptibility and progression.

METHODS

We compared human complementary DNA libraries from OA-affected and normal cartilage and synovium and selected 22 genes in addition to the estrogen receptor alpha and vitamin D receptor genes. Based on the availability of polymorphisms, we proceeded to test whether genetic variation at those genes affected susceptibility to or progression of radiographic knee OA over a 10-year period in 749 women (mean age 64 years) from the longitudinal Chingford Study.

RESULTS

After adjusting for age and body mass index, we observed significant associations at ADAM12, BMP2, CD36, COX2, and NCOR2 with 3 OA susceptibility traits (presence/absence of joint space narrowing [JSN], presence/absence of osteophytes, and Kellgren/Lawrence [K/L] score). For the OA progression traits (change over 10 years in the K/L score, osteophyte grade, and JSN grade), we found significant associations with ADAM12, CILP, OPG, and TNA. Overall, we observed 15 associations with nominal significance (P < 0.05) and, by permutation analysis, found that such a number would be observed by chance only 3.8% of the time. Although these tests require replication, the stronger genetic associations observed are unlikely to be attributable simply to multiple comparisons.

CONCLUSION

Our results suggest that OA severity and progression have a multigenic and feature-specific nature. These findings should encourage the development of genetic diagnostics for OA progression based on multiple SNPs and help unravel some of the complex disease mechanisms in OA.

The inheritance of hand osteoarthritis in Iceland

OBJECTIVE

To assess the contribution of genetics to hand osteoarthritis (HOA) and its subsets in the Icelandic population.

METHODS

A list of 2,919 HOA patients, constituting 1% of the Icelandic population, was compiled through nationwide sources. This patient list was cross-referenced with a comprehensive Icelandic genealogy database, enabling the use of algorithms to assess familiality of HOA. Two methods were used: the average pairwise kinship coefficient (KC) of the patients, and the relative risk (RR) of HOA in relatives of patients. In each case, the results were compared with 1,000 control sets of similar composition with regard to number, age, and sex, generated from the genealogy database.

RESULTS

The KC for patients was significantly higher than for the control sets and was proportional to the degree of both interphalangeal (IP) and thumb base (first carpometacarpal [CMC] joint) involvement. The RR of HOA in sisters of women in the study was 2.0 (P < 0.001), while the RR in spouses was not significantly different from that in controls. The RR increased with the severity of the disease. Thus, sisters of women with severe IP HOA had an RR of 5.0 and sisters of those with severe first CMC involvement had an RR of 6.9. The increased risk also extended beyond the nuclear family, with significantly increased risk in cousins.

CONCLUSION

Patients seeking medical services for HOA are more related to each other than matched controls, supporting the role of a genetic component in the disease. The genetic influence in both IP and first CMC HOA appears to be similar and increases with increasing severity of the disease.

Disabling spondyloarthrosis risk factors in valley of Mexico workers

BACKGROUND

The objective of this study was to describe the most prevalent physically disabling conditions for insured workers belonging to the Mexican Social Security Institute (IMSS) in the Valley of Mexico and to identify risk factors for disabling spondyloarthrosis.

METHODS

Retrospective cases and prevalent controls from IMSS clinics in the Mexico City metropolitan area were studied. Eighty cases were IMSS workers reporting disability due to spondyloarthrosis; 80 controls were active workers at the same workplace and shared the economic activity of the cases. The 1995 IMSS Disability Report was reviewed. From this report congenital conditions of the musculoskeletal system, obesity, history of trauma, and sociodemographic patient characteristics were assessed.

RESULTS

The most important risk factors were a history of spina bifida (odds ratio [OR] = 29.3, 95% confidence interval [95% CI] = 5.3-161; p = 0.0009), supernumerary vertebrae (OR = 21.3, 95% CI = 5.3-95; p = 0.0001), history of low back (lumbar) trauma (OR = 3.9, 95% CI = 1.9-8.3; p = 0.0004), flatfoot (OR = 11.7, 95% CI = 1.9-69, p = 0.02), and obesity (OR = 2.0, 95% CI = 1.06-4.03; p = 0.04).

CONCLUSIONS

A history of congenital deformity of the musculoskeletal system, spinal column trauma, and obesity were risk factors most associated with work disability due to spondyloarthrosis.

A large Icelandic family with early osteoarthritis of the hip associated with a susceptibility locus on chromosome 16p

OBJECTIVE

To describe a large kinship with inherited hip osteoarthritis (OA) and its associated susceptibility locus.

METHODS

Four generations of a kinship with familial hip OA were identified and characterized by family history and by clinical, radiographic, and histopathologic examination. In the genome-wide search for a susceptibility locus, OA cases were defined as those who had undergone total hip replacement associated with a clinical and radiographic diagnosis of hip OA. A genome-wide scan was performed using a framework set of microsatellite markers with an average spacing of 10 cM.

RESULTS

The hip OA of this family was indistinguishable from that of idiopathic, nonfamilial hip OA. There was no apparent evidence of spondyloepiphyseal dysplasia or other dysplasias usually associated with mutations in collagen genes. The genome-wide scan revealed a locus on chromosome 16p between 28 cM and 47 cM from the telomere, and this locus met the criteria for suggestive linkage (multipoint allele-sharing logarithm of odds [LOD] score 2.58, P = 1.6 x 10(-4)). Two additional regions with LOD scores of >1.5 were obtained.

CONCLUSION

We have identified and described the largest kinship with familial hip OA reported to date. Evidence for linkage in this family suggests that a gene for susceptibility to hip OA exists on chromosome 16p. This represents an independent identification of a susceptibility locus previously reported for hip OA in this geographic region.

Epidemiology of risk factors for osteoarthritis: systemic factors

Osteoarthritis (OA) appears to be a mechanically driven but chemically mediated disease process in which there is attempted (or aberrant) repair. Well established risk factors for OA include aging, obesity, gender, and, in selected subgroups, congenital anomalies. This review addresses less well established risk factors for OA that can impact joints through their effect on systemic metabolism rather than their contribution to local joint geometry and structure. These systemic risk factors include obesity; bone and bone density; nutrients, particularly those that function as antioxidants; and genetic factors. There is great opportunity for new prevention and intervention strategies as we expand our understanding of the role of these systemic risk factors.

The onset of generalized osteoarthritis in older women: a qualitative approach

OBJECTIVE

This qualitative study aims to investigate which factors are possibly associated with the onset of generalized osteoarthritis (OA) in older women.

METHODS

The study population was recruited from participants of a group course, "Coping With Osteoarthritis of the Hip or Knee." Twenty-three women with generalized OA were identified, 20 of whom participated in a semistructured interview at home. All data were self-reported by the subjects.

RESULTS

Hereditary factors were present in 17 women. Metabolic factors (such as impairments in carbohydrate and lipid metabolism, diabetes, etc.) were not prevalent. Twelve women thought that certain diets influenced their pain symptoms. Five women spontaneously mentioned their health status during the Second World War as a cause of their OA. Four considered too much stress as being a cause, and in 13 women symptoms started after a period of stressful life events or depression.

CONCLUSION

According to the respondents, depression, stress, and diets are associated with the onset and worsening of their generalized OA. Heredity and a low health status at a vulnerable age may also be important. These findings could generate new hypotheses that can be tested in future quantitative studies.

Association of genotypes affecting the expression of interleukin-1beta or interleukin-1 receptor antagonist with osteoarthritis

OBJECTIVE

The majority of cytokines and growth factors known to be involved in cartilage metabolism are synthesized by the chondrocytes themselves. They are up-regulated in osteoarthritic (OA) cartilage, resulting in 2 opposite phenotypes, TNFalpha(high) and TNFalpha(low), that are characterized by an elevated number of tumor necrosis factor alpha (TNFalpha)-positive and interleukin-1beta (IL-1beta)-positive chondrocytes, respectively. To establish a hierarchy among the cytokines and growth factors expressed in articular chondrocytes, this study investigated cytokine genes for known polymorphisms that may contribute to the deregulated expression in OA cartilage.

METHODS

Polymerase chain reaction techniques were performed either in a thermal cycler using standard methods or in a light cycler to analyze the frequencies of the TNFalpha (-308), IL-1 receptor antagonist (IL-1Ra) (intron 2), IL-1beta (exon 5), and IL-6 (-174) polymorphisms in 61 OA patients and 254 randomly chosen controls.

RESULTS

For the TNFalpha(low) phenotype, a statistically significant association was found with the less frequent allele of IL-1beta, which carries a single-basepair substitution in exon 5 and may contribute to the characteristic increase in IL-beta-positive chondrocytes. In contrast, the TNFalpha(high) phenotype was significantly associated with the less frequent allele of IL-1Ra, which carries two 86-bp repeats in the second intron and is assumed to lead to an elevated expression of the antagonist.

CONCLUSION

These results point to an association between the IL-1beta polymorphism and the TNFalpha(high) phenotype and between the IL-1Ra polymorphism and the TNFalpha(low) phenotype found in OA. Both associations suggest that IL-1beta may be more important than TNFalpha for the regulation of cytokine and growth factor expression in articular chondrocytes.

Prevalence of joint pain is higher among women in rural Japan than urban Japanese-American women in Hawaii

OBJECTIVE

Environmental factors such as farming contribute to the frequency of joint symptoms. The purpose of this study is to explore the possible role of environment (lifestyle), by comparing the prevalence of joint pain between Japanese in a rural farming district in Japan and in urban Hawaii.

SUBJECTS AND METHODS

Current or previous pain at specific joints was surveyed among 222 women in rural Japan and 638 Japanese women in urban Hawaii aged 60-79. The age adjusted prevalence was compared using logistic regression.

RESULTS

The prevalence of pain at one or more joints was approximately 70% in Japan and 50% in Hawaii. The prevalence of knee pain in Japan ranged from 36% at ages 60-69 years to 53% at 70-79 years (mean 41%), whereas knee pain affected only 20% of women in Hawaii in both age groups. The odds ratio (and 95% CI) was 3.2 (2.1, 4.8) for knee pain, and 4.0 (2.2, 7.4) for mid-back pain in Japan, compared with Hawaii. Pain was also significantly more common in Japan at the shoulder, elbow, and ankle, but not at other joints. Women in Japan were shorter and weighed less than in Hawaii. Adjustment for body mass index increased the odds ratios to 4.4 (2.9, 6.8) for knee, and 4.5 (2.4, 8.5) for mid-back pain.

CONCLUSION

Although the potential influence of cultural factors or other sources of bias cannot be ruled out, the large differences in the prevalence of pain at specific joints suggest that environmental factors are probably responsible, because both populations are of similar genetic stock.

Prevalence of hip osteoarthritis in Iceland

OBJECTIVE

To assess the prevalence of primary hip osteoarthritis (OA) in Iceland. To compare the prevalence of primary hip OA in Iceland with published rates of primary hip OA for related Scandinavian populations.

METHODS

Roentgenographs were examined of 1530 Icelandic people 35 years or older (653 males, 877 females) subjected to colon radiography during the years 1990-1996. The radiographs examined represent approximately 40% of all colon radiographs taken in Iceland during this period. After exclusion of non-primary hip OA cases, the minimum hip joint space was measured with a mm ruler. Presence of hip OA was defined as a minimum joint space of 2.5 mm or less on an anteroposterior radiograph. Intraclass correlation coefficients for inter and intraobserver variability of assessment of mm joint space were 0.91 and 0.95, respectively.

RESULTS

Of the 1517 people included, 227 hips in 165 patients (77 men, 88 women) were diagnosed as having radiological primary hip OA. The mean age at colon examination for these patients was 68 (35-89) years. The overall prevalence of coxarthrosis among all examined patients 35 years and older was 10.8% (12% for men, 10% for women), rising from 2% at 35-39 years to 35.4% for those 85 years or older. If the population structure (age and sex distribution) for those older than 35 years in Iceland was used to standardise prevalence for both Iceland and south Sweden (using previously published data for south Sweden), the age and sex standardised prevalence of hip OA for those older than 35 years in Iceland was 8%, compared with 1.2% for south Sweden.

CONCLUSIONS

The prevalence of radiological primary hip OA is very high in Iceland, and in excess of fivefold higher than the prevalence found by using similar techniques in studies on related populations in southern Scandinavia. The rate difference is particularly notable for those younger than 70 years.

The associations of bone mineral density and bone turnover markers with osteoarthritis of the hand and knee in pre- and perimenopausal women

OBJECTIVE

To determine whether Caucasian women ages 28-48 years with newly defined osteoarthritis (OA) would have greater bone mineral density (BMD) and less bone turnover over time than would women without OA.

METHODS

Data were derived from the longitudinal Michigan Bone Health Study. Period prevalence and 3-year incidence of OA were based on radiographs of the dominant hand and both knees, scored with the Kellgren/Lawrence (K/L) scale. OA scores were related to BMD, which was measured by dual-energy x-ray absorptiometry, and to serum osteocalcin levels, which were measured by radioimmunoassay.

RESULTS

The period prevalence of OA (K/L grade > or =2 in the knees or the dominant hand) was 15.3% (92 of 601), with 8.7% for the knees and 6.7% for the hand. The 3-year incidence of knee OA was 1.9% (9 of 482) and of hand OA was 3.3% (16 of 482). Women with incident knee OA had greater average BMD (z-scores 0.3-0.8 higher for the 3 BMD sites) than women without knee OA (P < 0.04 at the femoral neck). Women with incident knee OA had less change in their average BMD z-scores over the 3-year study period. Average BMD z-scores for women with prevalent knee OA were greater (0.4-0.7 higher) than for women without knee OA (P < 0.002 at all sites). There was no difference in average BMD z-scores or their change in women with and without hand OA. Average serum osteocalcin levels were lower in incident cases of hand OA (>60%; P = 0.02) or knee OA (20%; P not significant). The average change in absolute serum osteocalcin levels was not as great in women with incident hand OA or knee OA as in women without OA (P < 0.02 and P < 0.05, respectively).

CONCLUSION

Women with radiographically defined knee OA have greater BMD than do women without knee OA and are less likely to lose that higher level of BMD. There was less bone turnover among women with hand OA and/or knee OA. These findings suggest that bone-forming cells might show a differential response in OA of the hand and knee, and may suggest a different pathogenesis of hand OA and knee OA.