Sexual dimorphism in peri-articular tissue anatomy - More keys to understanding sex-differences in osteoarthritis?

Objective

Osteoarthritis prevalence differs between women and men; whether this is the result of differences in pre-morbid articular or peri-articular anatomical morphotypes remains enigmatic. Albeit sex within humans cannot be reduced to female/male, this review focusses to the sexual dimorphism of peri-articular tissues, given lack of literature on non-binary subjects.

Methods

Based on a Pubmed search and input from experts, we selected relevant articles based on the authors' judgement of relevance, interest, and quality; no "hard" bibliometric measures were used to evaluate the quality or importance of the work. Emphasis was on clinical studies, with most (imaging) data being available for the knee and thigh.

Results

The literature on sexual dimorphism of peri-articular tissues is reviewed: 1) bone size/shape, 2) subchondral/subarticular bone, 3) synovial membrane and infra-patellar fad-pad (IPFP), 4) muscle/adipose tissue, and 5) peri-articular tissue response to treatment.

Conclusions

Relevant sex-specific differences exist for 3D bone shape and IPFP size, even after normalization to body weight. Presence of effusion- and Hoffa-synovitis is associated with greater risk of incident knee osteoarthritis in overweight women, but not in men. When normalized to bone size, men exhibit greater muscle, and women greater adipose tissue measures relative to the opposite sex. Reduced thigh muscle specific strength is associated with incident knee osteoarthritis and knee replacement in women, but not in men. These observations may explain why women with muscle strength deficits have a poorer prognosis than men with similar deficits. A "one size/sex fits all" approach must be urgently abandoned in osteoarthritis research.

The design of a sample rapid magnetic resonance imaging (MRI) acquisition protocol supporting assessment of multiple articular tissues and pathologies in knee osteoarthritis

Objective

This expert opinion paper proposes a design for a state-of-the-art magnetic resonance image (MRI) acquisition protocol for knee osteoarthritis clinical trials in early and advanced disease. Semi-quantitative and quantitative imaging endpoints are supported, partly amendable to automated analysis. Several (peri-) articular tissues and pathologies are covered, including synovitis.

Method

A PubMed literature search was conducted, with focus on the past 5 years. Further, osteoarthritis imaging experts provided input. Specific MRI sequences, orientations, spatial resolutions and parameter settings were identified to align with study goals. We strived for implementation on standard clinical scanner hardware, with a net acquisition time ≤30 ​min.

Results

Short- and long-term longitudinal MRIs should be obtained at ≥1.5T, if possible without hardware changes during the study. We suggest a series of gradient- and spin-echo-sequences, supporting MOAKS, quantitative analysis of cartilage morphology and T2, and non-contrast-enhanced depiction of synovitis. These sequences should be properly aligned and positioned using localizer images. One of the sequences may be repeated in each participant (re-test), optimally at baseline and follow-up, to estimate within-study precision. All images should be checked for quality and protocol-adherence as soon as possible after acquisition. Alternative approaches are suggested that expand on the structural endpoints presented.

Conclusions

We aim to bridge the gap between technical MRI acquisition guides and the wealth of imaging literature, proposing a balance between image acquisition efficiency (time), safety, and technical/methodological diversity. This approach may entertain scientific innovation on tissue structure and composition assessment in clinical trials on disease modification of knee osteoarthritis.

Obesity, Metabolic Syndrome, and Osteoarthritis Require Integrative Understanding and Management

Osteoarthritis (OA) is a progressive chronic disease affecting the articular joints, leading to pain and disability. Unlike traditional views that primarily link OA to aging, recent understanding portrays it as a multifactorial degenerative disease of the entire joint. Emerging research highlights metabolic and immune dysregulation in OA pathogenesis, emphasizing the roles of obesity, dyslipidemia, and insulin resistance in altering joint homeostasis. Recent studies have increasingly focused on the complex role of white adipose tissue (WAT) in OA. WAT not only serves metabolic functions but also plays a critical role in systemic inflammation through the release of various adipokines. These adipokines, including leptin and adiponectin, have been implicated in exacerbating cartilage erosion and promoting inflammatory pathways within joint tissues. The overlapping global crises of obesity and metabolic syndrome have significantly impacted joint health. Obesity, now understood to contribute to mechanical joint overload and metabolic dysregulation, heightens the risk of developing OA, particularly in the knee. Metabolic syndrome compounds these risks by inducing chronic inflammation and altering macrophage activity within the joints. The multifaceted effects of obesity and metabolic syndrome extend beyond simple joint loading. These conditions disrupt normal joint function by modifying tissue composition, promoting inflammatory macrophage polarization, and impairing chondrocyte metabolism. These changes contribute to OA progression, highlighting the need for targeted therapeutic strategies that address both the mechanical and biochemical aspects of the disease. Recent advances in understanding the molecular pathways involved in OA suggest potential therapeutic targets. Interventions that modulate macrophage polarization, improve chondrocyte function, or normalize adipokine levels could serve as preventative or disease-modifying therapies. Exploring the role of diet, exercise, and pharmacological interventions in modulating these pathways offers promising avenues for reducing the burden of OA. Furthermore, such methods could prove cost-effective, avoiding the increase in access to healthcare.

Association between weight gain and knee osteoarthritis: a systematic review

OBJECTIVE

Although weight loss is recommended to manage knee osteoarthritis (KOA), adults tend to gain weight with age which may affect KOA symptoms and progression. We conducted a systematic review and data synthesis to investigate the association between weight gain and KOA, defined by clinical features, structural progression, and total knee replacement (TKR).

DESIGN

MEDLINE and EMBASE were systematically searched for controlled trials and cohort studies of participants with (or at risk of) KOA examining the relationship between weight gain and KOA clinical features (pain, function, quality of life), structural progression, and TKR. Risk of bias was assessed using the ROBINS-I tool. Results were organised by outcome, with meta-analyses performed where appropriate.

RESULTS

Twenty-three studies were included. Results showed significant detrimental effects of weight gain on pain (4 of 7 studies), stiffness (2 of 2 studies), function (5 of 6 studies), and the single studies examining quality of life, and clinical and radiographic KOA. Weight gain adversely affected cartilage (6 of 9 studies), bone marrow lesions (1 of 4 studies), meniscal damage (1 of 3 studies) and effusion/synovitis (1 of 1 study). Weight gain significantly increased TKR (3 of 6 studies): meta-analysis of 2 with available data demonstrated significant increases in TKR/5 kg weight gain in women, HR 1.34 (95% CI 1.18-1.51), and in men, HR 1.25 (95% CI 1.16-1.34).

CONCLUSIONS

Weight gain in adults is associated with increased clinical and structural KOA and TKR. Prevention of weight gain should be considered to improve outcomes in KOA.

Non-invasive brain stimulation for osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease, the prevalence of OA is increasing, and the elderly are the most common in patients with OA. OA has a severe impact on the daily life of patients, this increases the demand for treatment of OA. In recent years, the application of non-invasive brain stimulation (NIBS) has attracted extensive attention. It has been confirmed that NIBS plays an important role in regulating cortical excitability and oscillatory rhythm in specific brain regions. In this review, we summarized the therapeutic effects and mechanisms of different NIBS techniques in OA, clarified the potential of NIBS as a treatment choice for OA, and provided prospects for further research in the future.

Increased signal intensity, not volume variation of infrapatellar fat pad in knee osteoarthritis: A cross-sectional study based on high-resolution magnetic resonance imaging

BACKGROUND

Infrapatellar fat pad (IPFP) is regarded as an essential knee tissue involved in osteoarthritis (OA) for its potential structural-related or metabolism-related function. This cross-sectional study aims to identify which part is more related to OA.

METHODS

Patients with knee OA (n = 53) and healthy controls (n = 54) were prospectively recruited. Based on high-resolution magnetic resonance imaging with a slice thickness of only 0.35 mm, IPFP structural-related parameters (volume and maximal area), metabolism-related parameter (signal), degeneration indicators, and patellar maltracking indicators (patellar translation, patellofemoral angle, and Insall-Salvati ratio) were measured. IPFP volume (maximal area, and signal) was compared between healthy controls and OA patients. The level of significance for all comparisons was set as .05.

RESULTS

OA patients had higher IPFP signal (672.9 ± 136.9 vs 567.3 ± 63.6, p = .009), but no significant difference in IPFP volume or maximal area compared with healthy controls. In healthy controls, IPFP signal was positively associated with age (β = 1.481; 95% CI: 0.286-2.676; p = .018); IPFP maximal area was positively related to Insall-Salvati ratio (β = 0.001; 95% CI: 0.0003-0.0017; p = .039), but not associated with patellar translation and patellofemoral angle. In OA patients, IPFP signal was positively associated with cartilage loss (β = 0.005; 95% CI: 0.003-0.007; p = .013); no correlation between knee pain and IPFP volume or maximal area was observed.

CONCLUSIONS

The metabolism-related function of IPFP, which can be reflected by the IPFP signal, might play a more critical role in OA progression than its structural function.

Difference in pain and accuracy of two hyaluronic acid injection techniques for symptomatic knee osteoarthritis in overweight patients

Objectives

To evaluate differences of injection related pain, and the accuracy of the techniques in two groups of overweight patients, performing the anterolateral approach for one group (G1) and the superolateral approach for the second group (G2).

Material and methods

In the study, 126 knee joints from 86 osteoarthritis (OA) patients were evaluated. Inclusion criteria were body mass index (BMI) ≥ 25, absence of effusion and coagulopathy. Pain evaluation during injection was evaluated with Visual Analogue Scale (VAS), while accuracy of the procedure was evaluated with ultrasound (US).

Results

The patients’ mean age was 69.9 ±9.01, VAS for G1 group was 1.71 ±1.89, for G2 group was 1.74 ±1.31. Mean BMI was 29.69 ±2.86, for G1 group was 28.29 ±3.29, for G2 group was 30.32 ±2.41. No adverse events (AE) occurred in both studied groups. The accuracy rate of the procedure was 69.1% for G1 (38/55 knees), 95.7% for G2 (68/71 knees). No significant difference was found in VAS pain score between G1 and G2 group (p = 0.45). We found the significant correlation between BMI and VAS pain score in anterolateral accesses (G1) (r = 0.51; p < 0.005). No correlation was found between age and VAS pain score in anterolateral access (G1). For the superolateral access (G2), no correlation was found for age or BMI and VAS pain score.

Conclusions

Hyaluronic acid injection is safe therapeutic option for knee OA with no significant differences between anterolateral and superolateral approaches in terms of pain in overweight patients. However, higher BMI seems to be a predictor of pain in anterolateral access, and the superolateral approach should be preferred in this group of patients.

Association of infra-patellar fat pad size with age and body weight in children and adolescents

BACKGROUND

The infra-patellar fat pad (IPFP) represents a potential mediator between obesity, low grade inflammation, and knee osteoarthritis via endocrine pathways. Yet, not only in adults, but also in childhood obesity negatively impacts knee structures.

OBJECTIVE

The current study therefore investigated the sex-specific growth of the IPFP with age and body weight in healthy children and adolescents.

MATERIALS AND METHODS

Thirty young healthy subjects (60% girls; age 4-17 years, body weight 14-90 kg in girls and 29-105 kg in boys; BMI 12.2-32.4 kg/m²) without magnetic resonance imaging (MRI) knee pathology were studied. The IPFP volume was determined from sagittal T-1 weighted and proton-density spectral attenuated inversion recovery MRIs. The primary analysis focused on the sex-specific IPFP volume/body weight ratio as dependent, and age as independent variable, using linear regression models. A secondary analytic focus was the slope of the age-dependence of IPFP volume, without normalization to body weight.

RESULTS

There was no statistically significant association of the IPFP volume/body weight ratio with age in girls (p = 0.57) or boys (p = 0.31), the R² of ranging from -0.32 to 0.14. The ratio was greater in boys (0.54 ± 0.10 cm³/kg) than in girls (0.45 ± 0.07 cm³/kg) (p < 0.01). The IPFP volume increased by approx. 2 cm³ per annum in both girls and boys, without any indication of a non-linear relationship.

CONCLUSION

Our findings reveal that the ratio of the IPFP volume and body weight remains constant between age 4 and 17 in both normal weight girls and boys, and that the IPFP volume increases linearly with age throughout this period.

The effects of weight loss on imaging outcomes in osteoarthritis of the hip or knee in people who are overweight or obese: a systematic review

OBJECTIVE

To evaluate the structural effects of weight loss on hip or knee osteoarthritis (OA) and to summarize which structural joint pathologies have been examined and the evidence for the outcome measurement instruments applied.

DESIGN

Based on a pre-specified protocol (available: PROSPERO CRD42017065263), we conducted a systematic search of the bibliographic databases, Medline, Embase and Web of Science identifying longitudinal articles reporting the effects of weight loss on structural imaging outcomes in OA of the hip or knee in people who are overweight or obese.

RESULTS

From 1625 potentially eligible records, 14 articles (from 6 cohorts) were included. 2 cohorts were derived from RCTs. Evaluated pathologies were: articular cartilage (n = 7), joint space width (n = 3), bone marrow lesions (n = 5), synovitis (n = 2), effusion (n = 1), meniscus (n = 3), bone marrow density (n = 1) and infrapatellar fat pad (IPFP; n = 2). Cartilage showed conflicting results when evaluating cartilage thickness by direct thickness measurements. Compositional dGEMRIC and T2 mapping measures in early knee OA showed trends towards reduced cartilage degeneration. Joint space width on conventional radiographs showed no change. Weight loss reduced the size of the IPFP. Synovitis and effusion were not affected. Following weight loss DXA showed bone loss at the hip.

CONCLUSION

We did not find consistent evidence of the effects of weight loss on OA structural pathology in people who are overweight or obese. There is a need to achieve consensus on which structural pathologies and measurements to apply in weight loss and OA research.

Anterior cruciate ligament transection alters the n-3/n-6 fatty acid balance in the lapine infrapatellar fat pad

Background

The infrapatellar fat pad (IFP) of the knee joint has received lots of attention recently due to its emerging role in the pathogenesis of osteoarthritis (OA), where it displays an inflammatory phenotype. The aim of the present study was to examine the infrapatellar fatty acid (FA) composition in a rabbit (Oryctolagus cuniculus) model of early OA created by anterior cruciate ligament transection (ACLT).

Methods

OA was induced randomly in the left or right knee joint of skeletally mature New Zealand White rabbits by ACLT, while the contralateral knee was left intact. A separate group of unoperated rabbits served as controls. The IFP of the ACLT, contralateral, and control knees were harvested following euthanasia 2 or 8 weeks post-ACLT and their FA composition was determined with gas chromatography–mass spectrometry.

Results

The n-3/n-6 polyunsaturated FA (PUFA) ratio shifted in a pro-inflammatory direction after ACLT, already observed 2 weeks after the operation (0.20 ± 0.008 vs. 0.18 ± 0.009). At 8 weeks, the FA profile of the ACLT group was characterized with increased percentages of 20:4n-6 (0.44 ± 0.064 vs. 0.98 ± 0.339 mol-%) and 22:6n-3 (0.03 ± 0.014 vs. 0.07 ± 0.015 mol-%) and with decreased monounsaturated FA (MUFA) sums (37.19 ± 1.586 vs. 33.20 ± 1.068 mol-%) and n-3/n-6 PUFA ratios (0.20 ± 0.008 vs. 0.17 ± 0.008). The FA signature of the contralateral knees resembled that of the unoperated controls in most aspects, but had increased proportions of total n-3 PUFA and reduced MUFA sums.

Conclusions

These findings provide novel information on the effects of early OA on the infrapatellar FA profile in the rabbit ACLT model. The reduction in the n-3/n-6 PUFA ratio of the IFP is in concordance with the inflammation and cartilage degradation in early OA and could contribute to disease pathogenesis.

Electronic supplementary material

The online version of this article (10.1186/s12944-019-1008-5) contains supplementary material, which is available to authorized users.