Mechanical contributors to sex differences in idiopathic knee osteoarthritis

Short-term response of primary human meniscus cells to simulated microgravity

BACKGROUND

Mechanical unloading of the knee articular cartilage results in cartilage matrix atrophy, signifying the osteoarthritic-inductive potential of mechanical unloading. In contrast, mechanical loading stimulates cartilage matrix production. However, little is known about the response of meniscal fibrocartilage, a major mechanical load-bearing tissue of the knee joint, and its functional matrix-forming fibrochondrocytes to mechanical unloading events.

METHODS

In this study, primary meniscus fibrochondrocytes isolated from the inner avascular region of human menisci from both male and female donors were seeded into porous collagen scaffolds to generate 3D meniscus models. These models were subjected to both normal gravity and mechanical unloading via simulated microgravity (SMG) for 7 days, with samples collected at various time points during the culture.

RESULTS

RNA sequencing unveiled significant transcriptome changes during the 7-day SMG culture, including the notable upregulation of key osteoarthritis markers such as COL10A1, MMP13, and SPP1, along with pathways related to inflammation and calcification. Crucially, sex-specific variations in transcriptional responses were observed. Meniscus models derived from female donors exhibited heightened cell proliferation activities, with the JUN protein involved in several potentially osteoarthritis-related signaling pathways. In contrast, meniscus models from male donors primarily regulated extracellular matrix components and matrix remodeling enzymes.

CONCLUSION

These findings advance our understanding of sex disparities in knee osteoarthritis by developing a novel in vitro model using cell-seeded meniscus constructs and simulated microgravity, revealing significant sex-specific molecular mechanisms and therapeutic targets.

Sex differences in osteoarthritis prevalence, pain perception, physical function and therapeutics

OBJECTIVE

Women have a higher prevalence of osteoarthritis (OA) and worse clinical courses than men. However, the underlying factors and therapeutic outcomes of these sex-specific differences are incompletely researched. This review examines the current state of knowledge regarding sex differences in OA prevalence, risk factors, pain severity, functional outcomes, and use and response to therapeutics.

METHODS

PubMed database was used with the title keyword combinations "{gender OR sex} AND osteoarthritis" plus additional manual search of the included papers for pertinent references, yielding 212 references. Additional references were added and 343 that were reviewed for appropriateness.

RESULTS

Globally, women account for 60% of people with osteoarthritis with a greater difference after age 40. The higher risk for women may be due to differences in joint anatomy, alignment, muscle strength, hormonal influences, obesity, and/or genetics. At the same radiographic severity, women have greater pain severity than men, which may be explained by biologically distinct pain pathways, differential activation of central pain pathways, differences in pain sensitivity, perception, reporting, and coping strategies. Women have greater limitations of physical function and performance than men independent of BMI, OA severity, injury history, amount of weekly exercise. Women also have greater use of analgesic medications than men but less use of arthroplasty and poorer prognosis after surgical interventions.

CONCLUSIONS

The recognition of sex differences in OA manifestations and management could guide tailoring of sex-specific treatment protocols, and analysis of sex as a biological variable in future research would enhance development of precision medicine.

Injection of kaolin/carrageenan in the rat knee joint induces progressive experimental knee osteoarthritis

ABSTRACT

Osteoarthritis (OA), the most common joint disorder worldwide, is characterized by progressive degeneration of articular and periarticular structures, leading to physical and emotional impairments that greatly affect the quality of life of patients. Unfortunately, no therapy has been able to halt the progression of the disease. Owing to the complexity of OA, most animal models are only able to mimic a specific stage or feature of the human disorder. In this work, we demonstrate the intraarticular injection of kaolin or carrageenan leads to the progressive degeneration of the rat's knee joint, accompanied by mechanical hyperalgesia and allodynia, gait impairments (reduced contact area of the affected limb), and radiological and histopathological findings concomitant with the development of human grade 4 OA. In addition, animals also display emotional impairments 4 weeks after induction, namely, anxious and depressive-like behaviour, important and common comorbidities of human OA patients. Overall, prolonging kaolin or carrageenan-induced monoarthritis mimics several important physical and psychological features of human OA in both male and female rodents and could be further applied in long-term studies of OA-associated chronic pain.

Mechanical Unloading of Engineered Human Meniscus Models Under Simulated Microgravity: A Transcriptomic Study

Osteoarthritis (OA) primarily affects mechanical load-bearing joints, with the knee being the most common. The prevalence, burden and severity of knee osteoarthritis (KOA) are disproportionately higher in females, but hormonal differences alone do not explain the disproportionate incidence of KOA in females. Mechanical unloading by spaceflight microgravity has been implicated in OA development in cartilaginous tissues. However, the mechanisms and sex-dependent differences in OA-like development are not well explored. In this study, engineered meniscus constructs were generated from healthy human meniscus fibrochondrocytes (MFC) seeded onto type I collagen scaffolds and cultured under normal gravity and simulated microgravity conditions. We report the whole-genome sequences of constructs from 4 female and 4 male donors, along with the evaluation of their phenotypic characteristics. The collected data could be used as valuable resources to further explore the mechanism of KOA development in response to mechanical unloading, and to investigate the molecular basis of the observed sex differences in KOA.

Engineered Human Meniscus in Modeling Sex Differences of Knee Osteoarthritis in Vitro

Background: Osteoarthritis (OA) primarily affects mechanical load-bearing joints. The knee joint is the most impacted by OA. Knee OA (KOA) occurs in almost all demographic groups, but the prevalence and severity are disproportionately higher in females. The molecular mechanism underlying the pathogenesis and progression of KOA is unknown. The molecular basis of biological sex matters of KOA is not fully understood. Mechanical stimulation plays a vital role in modulating OA-related responses of load-bearing tissues. Mechanical unloading by simulated microgravity (SMG) induced OA-like gene expression in engineered cartilage, while mechanical loading by cyclic hydrostatic pressure (CHP), on the other hand, exerted a pro-chondrogenic effect. This study aimed to evaluate the effects of mechanical loading and unloading via CHP and SMG, respectively, on the OA-related profile changes of engineered meniscus tissues and explore biological sex-related differences.

Methods: Tissue-engineered menisci were made from female and male meniscus fibrochondrocytes (MFCs) under static conditions of normal gravity in chondrogenic media and subjected to SMG and CHP culture. Constructs were assayed via histology, immunofluorescence, GAG/DNA assays, RNA sequencing, and testing of mechanical properties.

Results: The mRNA expression of ACAN and COL2A1, was upregulated by CHP but downregulated by SMG. COL10A1, a marker for chondrocyte hypertrophy, was downregulated by CHP compared to SMG. Furthermore, CHP increased GAG/DNA levels and wet weight in both female and male donors, but only significantly in females. From the transcriptomics, CHP and SMG significantly modulated genes related to the ossification, regulation of ossification, extracellular matrix, and angiogenesis Gene Ontology (GO) terms. A clear difference in fold-change magnitude and direction was seen between the two treatments for many of the genes. Furthermore, differences in fold-change magnitudes were seen between male and female donors within each treatment. SMG and CHP also significantly modulated genes in OA-related KEGG pathways, such as mineral absorption, Wnt signalling pathway, and HIF-1 signalling pathway.

Conclusion: Engineered menisci responded to CHP and SMG in a sex-dependent manner. SMG may induce an OA-like profile, while CHP promotes chondrogenesis. The combination of SMG and CHP could serve as a model to study the early molecular events of KOA and potential drug-targetable pathways.

Long-term effects of shoe mileage on knee and ankle joints muscle co-contraction during walking in females with genu varus

BACKGROUND

Shoe mileage may influence the risk of sustaining injuries during walking.

RESEARCH QUESTION

What are the effects of shoe mileage on knee and ankle muscle co-contraction during walking in females with genu varus?

METHODS

Fifteen healthy and 15 women diagnosed with genu varus received a new pair of running shoes. They were asked to wear these shoes over 6 months. Pre and post intervention, muscle activities of the dominant limb were recorded during a walking test at preferred gait speed. Two dependent variables were assessed to examine muscle co-contraction: (1) directed co-contraction ratios of agonists and antagonists, and (2) general joint muscle co-contraction.

FINDINGS

Results demonstrated significant main effects of the "shoe" factor for general ankle co-contraction during the push-off phase (p = 0.013, d = 1.503). Irrespective of experimental group, paired comparisons revealed significantly lower general ankle co-contraction during the push-off phase after the intervention. A significant main effects of "shoe" for general knee co-contraction during loading phase (p = 0.025, d = 0.895) was also observed. In both groups, paired comparison revealed significantly lower general knee co-contraction during the push-off phase in the post condition. We did not find any significant main effect of group nor group-by-shoe interaction for general ankle co-contraction during the stance phase. Likewise, we did not observe any significant main effect of "shoe", "group" and "group-by-shoe" interaction for mediolateral directed knee co-contraction during stance phase of walking (p > 0.05).

SIGNIFICANCE

Our findings showed that the shoe mileage but not the genu varus condition affects the general and directed co-contraction of the muscles stabilizing the knee and ankle joints. Together with the observed findings on ankle and knee muscle co-contraction, it is essential to change running shoes after a long wearing time in both healthy and genu varus females.

Influence of sex and gender on the management of late-stage knee osteoarthritis

PURPOSE

The exact nature of sex and gender differences in knee osteoarthritis (OA) among patient candidates for total knee arthroplasty (TKA) remains unclear and requires better elucidation to guide clinical practice. The purpose of this investigation was to survey physician practices and perceptions about the influence of sex and gender on knee OA presentation, care, and outcomes after TKA.

METHODS

The survey questions were elaborated by a multidisciplinary scientific board composed of 1 pain specialist, 4 orthopedic specialists, 2 physiatrists, and 1 expert in gender medicine. The survey included 5 demographic questions and 20 topic questions. Eligible physician respondents were those who treat patients during all phases of care (pain specialists, orthopedic specialists, and physiatrists). All survey responses were anonymized and handled via remote dispersed geographic participation.

RESULTS

Fifty-six physicians (71% male) accepted the invitation to complete the survey. In general, healthcare professionals expressed that women presented worse symptomology, higher pain intensity, and lower pain tolerance and necessitated a different pharmacological approach compared to men. Pain and orthopedic specialists were more likely to indicate sex and gender differences in knee OA than physiatrists. Physicians expressed that the absence of sex and gender-specific instruments and indications is an important limitation on available studies.

CONCLUSIONS

Healthcare professionals perceive multiple sex and gender-related differences in patients with knee OA, especially in the pre- and perioperative phases of TKA. Sex and gender bias sensitivity training for physicians can potentially improve the objectivity of care for knee OA among TKA candidates.

Understanding the Impact of Sex and Gender in Osteoarthritis: Assessing Research Gaps and Unmet Needs

Osteoarthritis (OA) affects more than 300 million individuals globally, with higher prevalence in women than in men. In addition, OA affects women and men differently, with women demonstrating both increased disease severity and disability. The Society for Women's Health Research (SWHR) convened an interdisciplinary group of expert researchers and clinicians for a roundtable meeting to review the current state of the science on OA and to identify knowledge gaps in the scientific literature, especially as they relate to the topics of sex and gender. The current review summarizes discussions from the roundtable and prioritizes areas of need that warrant further attention in OA research, diagnosis, care, and education. Improvements in basic and clinical research, clinical practice, patient education, and policy are needed to allow for better understanding as to the pathogenesis of sex- and gender-related disparities in OA.

Long-term effects of shoe mileage on ground reaction forces and lower limb muscle activities during walking in individuals with genu varus

BACKGROUND

Shoe mileage is an important factor that may influence the risk of sustaining injuries during walking. The aims of this study were to examine the effects of shoe mileage on ground reaction forces and activity of lower limb muscles during walking in genu varus individuals compared with controls.

METHODS

Fifteen healthy and 15 genu varus females received a new pair of running shoes. They were asked to wear these shoes over 6 months. Pre and post intervention, mechanical shoe testing was conducted and ground reaction forces and muscle activities of the right leg were recorded during walking at preferred gait speed.

FINDINGS

Significant group-by-time interactions were found for shoe stiffness, antero-posterior and vertical impact peak. We observed higher shoe stiffness and lower impact peaks after intervention in both groups with larger effect sizes in genu varus. Significant group-by-time interactions were identified for vastus medialis (loading phase) and rectus femoris (loading and push-off). For vastus medialis, significant decreases were found from pre-to-post during the loading phase in the control group. Rectus femoris activity was higher post intervention during the loading and push-off phases in both groups with larger effect sizes in genu varus.

INTERPRETATION

Our findings indicate that the observed changes in ground reaction forces are more prominent in genu varus individuals. Together with our findings on shoe stiffness, it seems appropriate to change running shoes after an intense wearing time of 6 months, particularly in genu varus individuals.

Association between the severity of symptomatic knee osteoarthritis and cumulative metabolic factors

BACKGROUND

The association between cumulative metabolic syndrome (MS) factors and knee osteoarthritis (KOA) has been highlighted over the past two decades.

AIMS

To clarify the relationship between cumulative MS factors and symptomatic KOA.

METHODS

A cross-sectional survey involving 119 women aged 45-88 years who were scheduled to undergo knee surgery was conducted. They were stratified into tertiles of symptoms as assessed by the Japanese Orthopedic Association score for KOA. Multinomial logistic regressions were performed using the severity of symptomatic KOA as the dependent variable and each MS factor or the cumulative MS factors as the independent variables.

RESULTS

Logistic regression analyses were performed with the upper tertile of stratified symptoms of subjects used as the reference group. After adjustment for confounders, KOA patients who had two (p = 0.004) or three or more (p < 0.0001) MS factors were significantly more likely to have severe symptoms compared to those who had no MS factors. MS factors excluding obesity were similarly analyzed. Even after additional adjustment for body mass index (BMI), KOA patients who had two or more (p = 0.005) MS factors were significantly more likely to have severe symptoms.

CONCLUSION

Among KOA female patients diagnosed using radiographic definition, the severity of symptomatic KOA was significantly associated with hypertension, dyslipidemia, and the number of MS factors after adjustment for age, BMI, strength of the knee extensor, and Kellgren-Lawrence grade. The severity of radiographic KOA was not associated with any MS factor or cumulative MS factors.

Neuropathic pain in end-stage hip and knee osteoarthritis: differential associations with patient-reported pain at rest and pain on activity

OBJECTIVE

We investigated whether pain at rest and pain on activity were differentially associated with neuropathic pain scores in individuals with end-stage hip and knee OA.

DESIGN

Study participants were 843 patients with hip or knee OA scheduled for total joint arthroplasty. In pre-surgery questionnaires, measures of socio-demographics, health status, medication use, neuropathic pain (painDETECT), pain at rest and pain on activity (WOMAC pain items), depression (HADS) and pain catastrophizing (PCS) were collected. Multivariable linear regression models were estimated for men and women separately to examine the association between neuropathic pain scores (outcome) and study measures, entered in blocks.

RESULTS

Sample mean age was 65.1 years (SD: 9.6); 57.1% were women. Mean painDETECT scores were significantly higher (P ≤ֹ 0.001) for women (11.2 ± 6.6 out of 38) than men (9.3 ± 7.0), with 35.6% of women and 27.7% of men meeting cut-offs for possible or likely neuropathic pain. In the final regression model for women, the coefficients for both types of pain were statistically significant, although the coefficient for pain at rest was 1.6 times greater than that for pain on activity. For men, only pain at rest was significantly associated with neuropathic pain scores.

CONCLUSIONS

Findings support that possible neuropathic pain is experienced by a notable proportion of patients with end-stage hip and knee OA and is more strongly associated with pain at rest than pain on activity, particularly in men. Clinical presentation of pain at rest may warrant more thorough evaluation for potential neuropathic pain and have implications for appropriate pain management.

Key components and potential benefits of a comprehensive approach to women's musculoskeletal health

Over the last 40 years there has been a significant increase in the number of female athletes, as well as a rise in musculoskeletal injuries observed in women. There is sufficient evidence from past medical research identifying various musculoskeletal injuries and conditions that more commonly affect women, such as osteoarthritis, osteoporosis, stress fractures, and anterior cruciate ligament tears. Several women's sports medicine and musculoskeletal health programs have been developed throughout the United States in an attempt to provide more tailored care to the female athlete. The goal of a comprehensive approach to women's musculoskeletal health is to create an interdisciplinary team to facilitate treatment for a variety of injuries and related conditions. This manuscript outlines the musculoskeletal conditions that commonly affect women and highlights the various etiologies of these sex disparities. We discuss the role of interdisciplinary women's musculoskeletal health and sports medicine programs, and define the potential benefits of such an approach. Future studies should focus on assessing the outcomes of multidisciplinary women's sports medicine programs as current literature in this area is lacking.

Characterization of osteoarthritic human knees indicates potential sex differences

BACKGROUND

The prevalence of osteoarthritis is higher in women than in men in every age group, and overall prevalence increases with advancing age. Sex-specific differences in the properties of osteoarthritic joint tissues may permit the development of sex-specific therapies. Sex hormones regulate cartilage and bone development and homeostasis in a sex-dependent manner. Recent in vitro studies show that the vitamin D3 metabolite 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3] also has sex-specific effects on musculoskeletal cells, suggesting that vitamin D3 metabolites may play a role in osteoarthritis-related sex-specific differences. The purpose of this study was to determine if sex-specific differences exist in synovial fluid and knee tissues isolated from male and female patients with severe knee osteoarthritis. We determined the presence of vitamin D3 metabolites, inflammatory cytokines, growth factors, and matrix metalloproteinases (MMPs) in synovial fluid and assessed responses of articular chondrocytes and subchondral osteoblasts to 17β-estradiol, dihydrotestosterone, and 1α,25(OH)2D3.

METHODS

Samples from knee joints of 10 Caucasian male and 10 Caucasian female patients with advanced osteoarthritis aged 65 to 75 years were obtained from total knee arthroplasty. Vitamin D metabolites, cytokines, MMPs, and growth factors in the synovial fluid were measured. Primary cultures of chondrocytes were isolated from fibrillated articular cartilage adjacent to osteoarthritis lesions and minimally affected cartilage distal to the lesion. Osteoblasts were isolated from the subchondral bone. Expression of receptors for 17β-estradiol and 1α,25(OH)2D3 was assessed by real-time PCR. Chondrocytes and osteoblasts were treated with 10(-8) M 17β-estradiol, dihydrotestosterone, or 1α,25(OH)2D3 and effects on gene expression and protein synthesis determined.

RESULTS

Histology of the articular cartilage confirmed advanced osteoarthritis. Sex differences were found in synovial fluid levels of vitamin D metabolites, cytokines, and metalloproteinases as well as in the cellular expression of receptors for 17β-estradiol and 1α,25(OH)2D3. Male cells were more responsive to 1α,25(OH)2D3 and dihydrotestosterone, whereas 17β-estradiol-affected female cells.

CONCLUSIONS

These results demonstrate that there are underlying sex differences in knee tissues affected by osteoarthritis. Our findings do not address osteoarthritis etiology but have implications for different prevention methods and treatments for men and women. Further research is needed to better understand these sex-based differences.

Functional Impairment Is a Risk Factor for Knee Replacement in the Multicenter Osteoarthritis Study

BACKGROUND

Debilitating pain associated with knee osteoarthritis (OA) often leads patients to seek and complete total knee arthroplasty (TKA). To date, few studies have evaluated the relation of functional impairment to the risk of TKA, despite the fact that OA is associated with functional impairment.

QUESTIONS/PURPOSES

The purpose of our study was to (1) evaluate whether function as measured by WOMAC physical function subscale was associated with undergoing TKA; and (2) whether any such association varied by sex.

METHODS

The National Institutes of Health-funded Multicenter Osteoarthritis Study (MOST) is an observational cohort study of persons aged 50 to 79 years with or at high risk of symptomatic knee OA who were recruited from the community. All eligible subjects with complete data were included in this analysis. Our study population sample consisted of 2946 patients with 5796 knees; 1776 (60%) of patients were women. We performed a repeated-measures analysis using baseline WOMAC physical function score to predict the risk of TKA from baseline to 30 months and WOMAC score at 30 months to predict risk of incident TKA from 30 months to 60 months. We used generalized estimating equations to account for the correlation between two knees within an individual and across the two periods. We calculated relative risk (RR) of TKA over 30 months by WOMAC function using a score of 0 to 5 as the referent in multiple binomial regressions with log link.

RESULTS

Those with the greatest functional impairment (WOMAC scores 40-68; 62 TKAs in 462 knee periods) had 15.5 times (95% confidence interval [CI], 7.6-31.8; p<0.001) the risk of undergoing TKA over 30 months compared with the referent group (12 TKAs in 3604 knee periods), adjusting for basic covariates, and 5.9 times (95% CI, 2.8-12.5; p<0.001) the risk after further adjusting for knee pain severity. At every level of functional limitation, the RR for TKA for women was higher than for men, but interaction with sex did not reach significance after adjustment for covariates including ipsilateral pain (p=0.138).

CONCLUSIONS

Baseline physical function appears to be an important element in patients considering TKA. Future studies should examine whether interventions to improve function can reduce the need for TKA.

LEVEL OF EVIDENCE

Level III, observational cohort study.

Male and female differences in musculoskeletal disease

Gender differences exist in the presentation of musculoskeletal disease, and recognition of the differences between men and women's burden of disease and response to treatment is key in optimizing care of orthopaedic patients. The role of structural anatomy differences, hormones, and genetics are factors to consider in the analysis of differential injury and arthritic patterns between genders.

A sex comparison of ambulatory mechanics relevant to osteoarthritis in individuals with and without asymptomatic varus knee alignment

The prevalence of medial knee osteoarthritis is greater in females and is associated with varus knee alignment. During gait, medial knee osteoarthritis has been linked to numerous alterations. Interestingly, there has been no research exploring sex differences during walking in healthy individuals with and without varus alignment. Therefore, the gait mechanics of 30 asymptomatic individuals with varus knees (15 females) and 30 normally-aligned controls (15 females) were recorded. Gait parameters associated with medial knee osteoarthritis were analyzed with two-factor analyses of variance. In result, varus males exhibited the greatest peak knee adduction moments, while normal females showed the greatest peak hip adduction angles and pelvic drop excursions. By sex, females exhibited greater peak hip adduction angles and moments and greater pelvic drop excursion, but lesser peak knee adduction angles. By alignment type, varus subjects exhibited greater peak knee adduction angles and moments, midstance knee flexion angles and excursion, and eversion angles and lateral ground reaction forces, but lesser peak hip adduction angles. In conclusion, females generally presented with proximal mechanics related to greater hip adduction, whereas males presented with more knee adduction. Varus subjects demonstrated a number of alterations associated with medial knee osteoarthritis. The differential sex effects were far less conclusive.

Non-invasive quantification of lower limb mechanical alignment in flexion

OBJECTIVE

Non-invasive navigation techniques have recently been developed to determine mechanical femorotibial alignment (MFTA) in extension. The primary aim of this study was to evaluate the precision and accuracy of an image-free navigation system with new software designed to provide multiple kinematic measurements of the knee. The secondary aim was to test two types of strap material used to attach optical trackers to the lower limb.

METHODS

Seventy-two registrations were carried out on 6 intact embalmed cadaveric specimens (mean age: 77.8 ± 12 years). A validated fabric strap, bone screws and novel rubber strap were used to secure the passive tracker baseplate for four full experiments with each knee. The MFTA angle was measured under the conditions of no applied stress, valgus stress, and varus stress. These measurements were carried out at full extension and at 30°, 40°, 50° and 60° of flexion. Intraclass correlation coefficients, repeatability coefficients, and limits of agreement (LOA) were used to convey precision and agreement in measuring MFTA with respect to each of the independent variables, i.e., degree of flexion, applied coronal stress, and method of tracker fixation. Based on the current literature, a repeatability coefficient and LOA of ≤ 3° were deemed acceptable.

RESULTS

The mean fixed flexion for the 6 specimens was 12.8° (range: 6-20°). The mean repeatability coefficient measuring MFTA in extension with screws or fabric strapping of the baseplate was ≤ 2°, compared to 2.3° using rubber strapping. When flexing the knee, MFTA measurements taken using screws or fabric straps remained precise (repeatability coefficient ≤ 3°) throughout the tested range of flexion (12.8-60°); however, using rubber straps, the repeatability coefficient was >3° beyond 50° flexion. In general, applying a varus/valgus stress while measuring MFTA decreased precision beyond 40° flexion. Using fabric strapping, excellent repeatability (coefficient ≤ 2°) was observed until 40° flexion; however, beyond 50° flexion, the repeatability coefficient was >3°. As was the case with precision, agreement between the invasive and non-invasive systems was satisfactory in extension and worsened with flexion. Mean limits of agreement between the invasive and non-invasive system using fabric strapping to assess MFTA were 3° (range: 2.3-3.8°) with no stress applied and 3.9° (range: 2.8-5.2°) with varus and valgus stress. Using rubber strapping, the corresponding values were 4.4° (range: 2.8-8.5°) with no stress applied, 5.5° (range: 3.3-9.0°) with varus stress, and 5.6° (range: 3.3-11.9°) with valgus stress.

DISCUSSION

Acceptable precision and accuracy may be possible when measuring knee kinematics in early flexion using a non-invasive system; however, we do not believe passive trackers should be mounted with rubber strapping such as was used in this study. Flexing the knee appears to decrease the precision and accuracy of the system. The functions of this new software using image-free navigation technology have many potential clinical applications, including assessment of bony and soft tissue deformity, pre-operative planning, and post-operative evaluation, as well as in further pure research comparing kinematics of the normal and pathological knee.

Older Adults without Radiographic Knee Osteoarthritis: Knee Alignment and Knee Range of Motion

This study describes knee alignment and active knee range of motion (ROM) in a community-based group of 78-year old adults (n = 143) who did not have radiographic evidence of knee osteoarthritis in either knee (KL < 2). Although knee malalignment is a risk factor for knee osteoarthritis, most women and men had either valgus or varus alignments. Notably, no men were valgus in both knees. Women with both knees valgus had significantly greater body mass index (P > 0.001) than women with varus or straight knees. Men and women with valgus or varus knee alignments had generally lower ROM than individuals with both knees straight. In summary, this study highlights the complex relationships among knee alignment, ROM, body mass index, and gender in elderly adults without radiographic knee osteoarthritis.

Association between childhood overweight measures and adulthood knee pain, stiffness and dysfunction: a 25-year cohort study

OBJECTIVE

To describe the associations between overweight measures in childhood and knee pain, stiffness and dysfunction among adults 25 years later.

METHODS

Subjects broadly representative of the Australian population (n=449, aged 31-41 years, female 48%) were selected from the Australian Schools Health and Fitness Survey of 1985. Height, weight and knee injury were recorded and knee pain was assessed using the Western Ontario and McMaster Universities osteoarthritis index (WOMAC). Childhood height, weight and knee injury had been measured according to standard protocols 25 years earlier and body mass index (BMI) and percentage overweight were calculated.

RESULTS

The prevalence of knee pain was 34% and overweight in childhood and adulthood was 7% and 48%, respectively. Overall, there were no significant associations between childhood overweight measures and total WOMAC knee pain, stiffness and dysfunction scores in adulthood. However, in men, overweight in childhood was associated with adulthood WOMAC pain (relative risk (RR) 1.72, 95% CI 1.11 to 2.69) and childhood weight and BMI were associated with WOMAC stiffness and dysfunction. Childhood weight, BMI and overweight were all associated with the presence of adulthood walking knee pain in men and the whole sample. Most of these associations were independent of adult overweight measures. Subjects who were overweight in both childhood and adult life had a significant increase in the risk and prevalence of adulthood walking pain (RR=2.42, 95% CI 1.06 to 5.53).

CONCLUSIONS

Childhood overweight measures were significantly associated with adulthood knee mechanical joint pain, stiffness and dysfunction among men, independent of adult overweight, suggesting that childhood overweight may lead to later knee symptoms in men.

[Clinical factors and findings in knee arthroscopy of patients with knee arthrosis candidates for conversion to total replacement]

OBJECTIVES

To identify those clinical characteristic and arthroscopic findings in patients with knee arthrosis that are associated with worsening of the disease and subsequent total knee arthroplasty (TKA).

METHOD

A retrospective, descriptive study was conducted on 78 consecutive patients (88 knees) who underwent knee arthroscopy for arthrosis. The study included 44 women and 34 men, with a mean age of 58.9 years (range: 37-78 years). After a mean follow-up of 50.4 months (range: 12-96 months), those patients who progressed towards TKA were identified. A logistic regression model was applied to recognise the factors associated with deterioration of the arthrosis, with consequent progression towards a TKA.

RESULTS

Twenty-four out of the 88 knees progressed towards a TKA (27.3%) within a mean time of 13.5 months after arthroscopy (range: 13-29 months). The clinical characteristics that showed a significant association with poor progression of the arthrosis were: female gender (0.02) and Ahlbäck 2 (P=.04). Arthroscopic finding that proved significant correlation with worsening of the arthrosis towards TKA were: meniscal tears of the posterior horn (P=.02), meniscectomies above 60% (P=.03), and 2nd degree chondral lesions in loading areas of the medial femoral condyle (P=.02).

CONCLUSION

The variables associated with a greater chance of progressing towards a TKA after a knee arthroscopy due to arthrosis in this study were, female gender, grade 2 radiographic arthrosis, posterior horn meniscal lesions, meniscectomies over 60%, and chondral lesions in loading area of the medial femoral condyle.

Addressing the gaps: sex differences in osteoarthritis of the knee

An introduction to the accompanying three papers.