316 research outputs found
Association between bone marrow lesions & synovitis and symptoms in symptomatic knee osteoarthritis
No full textObjective: Bone marrow lesions (BMLs) on MRI are typically subchondral in location, however, a proportion occur at knee ligament attachments and also include a cyst-like component. Our aim was to determine whether the volume of BML subtypes and synovial tissue volume (STV) was associated with symptoms in symptomatic knee OA. Method: Images were acquired in a sub-sample who had taken part in a randomised trial of vitamin D therapy in knee OA (UK-VIDEO). Contrast-enhanced (CE) MRI was performed annually. In those who had ≥1 follow-up and a baseline scan (N = 50), STV and BML volume was assessed. BMLs were categorised by location and by the presence/absence of a cyst-like component. WOMAC was assessed annually. We used fixed-effects panel-regression modelling to examine the association between volume and symptoms. Results: There was no association between knee pain and total subchondral BML volume (b = 0.3 WOMAC units, 95% CI -0.3 to 1.0) or total ligament-based BML volume (b = 1.9, 95% CI -1.6 to 5.3). The volume of subchondral BMLs with a cyst-like component was not associated with pain (b = 0.8, 95% CI -0.5 to 2.1) however, the volume of the cyst-like component itself was associated with pain (b = 51.8, 95% CI 14.2 to 89.3). STV was associated with pain (b = 2.2, 95% CI 0.6 to 3.7). Conclusion: The volume of the cyst-like component from subchondral BMLs with a cyst-like component was associated with knee pain. BML location, however, did not influence symptoms. STV was also associated with knee symptoms.</p
Nonlinear system analysis of local reflex control of locust hind limbs
No full textNonlinear Volterra type system identification models coupled with a Gaussian White Noise (GWN) stimulation signal provide an experimentally convenient and quick way to investigate the often complex and nonlinear interactions between the mechanical and neural elements of invertebrate reflex limb control systems. Previous steady state analysis has allowed the neurons in such systems to be categorised by their sensitivity to position, velocity or acceleration (system dynamics) and has improved understanding of network function. These neurons, however, are known to adapt their output amplitude or spike firing rate during repetitive stimulation and this transient response may be more important than the steady state response for reflex limb control. Furthermore, whilst the use of GWN for system identification can be theoretically and experimentally justified, the properties of this signal are very different from those received by the sensory, inter and motor neurons in the neural networks which monitor the position of the locusts leg under natural operating conditions. The current study provides improvements to the previously used experimental methods, equipment and nonlinear system identification methods. Validation of the models using biologically more realistic stimulation signals has been carried out to determine where they perform well and to identify their limitations. The use of the parsimonious cascade model structure, applied in a quasi stationary fashion coupled with Monte Carlo (MC) simulations, has been shown to provide a useful tool for the characterisation of the dynamics and nonlinear responses of the neuromuscular elements in a locust’s reflex limb control system during both transient and steady state response sections. This method been applied to test the null hypothesis that the dynamics and nonlinear responses of the locust’s Fast Extensor Tibia (FETi) motor neuron system are the same during transient and steady state sections. It can be concluded that key FETi system dynamics remain relatively unchanged during repetitive stimulation while output amplitude adaptation is occurring. Whilst some evidence of a significant change was found in parts of the system’s nonlinear response, the effect was small and probably of little physiological relevance. Analysis using biologically more realistic stimulation reinforces this conclusion
High systemic bone mineral density increases the risk of incident knee OA and joint space narrowing, but not radiographic progression of existing knee OA: the MOST study
No full textObjectives: previous studies suggest that high systemic bone mineral density (BMD) is associated with incident knee osteoarthritis (OA) defined by osteophytes but not with joint space narrowing (JSN), and are inconsistent regarding BMD and progression of existing OA. The association of BMD with incident and progressive tibiofemoral OA was tested in a large prospective study of men and women aged 50–79 years with or at risk for knee OA.Methods: baseline and 30-month weight-bearing posteroanterior and lateral knee radiographs were scored for Kellgren-Lawrence (K-L) grade, JSN and osteophytes. Incident OA was defined as the development of K-L grade ?2 at follow-up. All knees were classified for increases in grade of JSN and osteophytes from baseline. The association of gender-specific quartiles of baseline BMD with risk of incident and progressive OA was analysed using logistic regression, adjusting for covariates.Results: the mean (SD) age of 1754 subjects was 63.2 (7.8) years and body mass index was 29.9 (5.4) kg/m2. In knees without baseline OA, higher femoral neck and whole body BMD were associated with an increased risk of incident OA and increases in grade of JSN and osteophytes (p<0.01 for trends); adjusted odds were 2.3–2.9-fold greater in the highest compared with the lowest BMD quartiles. In knees with existing OA, progression was not significantly related to BMD.Conclusions: in knees without OA, higher systemic BMD was associated with a greater risk of the onset of JSN and K-L grade ?2. The role of systemic BMD in early knee OA pathogenesis warrants further investigatio
Suburbanization and amphibians: designed ecological solutions
No full textRegulations guiding land development around seasonal isolated wetlands disregard habitat requirements for specialized faunal inhabitants. This oversight needs to be addressed at multiple scales in order to sustain future seasonal pond inhabitants. In particular, pool-breeding amphibians are suffering worldwide decline and are susceptible to water quality, temperature, hydrology and watershed impacts. The complex aquatic-terrestrial lifecycle of amphibians
makes them sensitive to terrestrial habitat alterations and fragmentation. The temporal variation in hydroperiod within individual ponds and variation in
hydrology across ponds within a landscape create a stochastic system. In these systems amphibian populations likely function as metapopulations, and rely on juvenile dispersal and rescue effects to counter local extinction. Given the limited regulations at the local, state and federal level, maintaining amphibian breeding
populations will require efforts at the pond, migration corridor, upland habitat, watersheds and regional connectivity levels. Addressing these gaps requires
further basic research to expose hidden aspects of amphibian lifecycle patterns, in part due to their fossorial nature as well as the challenges of interpreting
metapopulation connectivity. Addressing the gaps also requires translating the ecological requirements into preservation tactics within the pressures of land
development, which poses substantial challenges. I utilized designed experiments, which serve as a hybrid research and planning approach, to navigate these complex circumstances. Here, I present a series of large-scale field experiments situated within a 500-hectare privately owned suburban development project located in Tuxedo, New York. The field experiments were implemented as part of the masterplanning process with the aim of exposing and
addressing several of these regulatory gaps from both a basic science and applied solutions perspective. A series of drift fence and pit-fall trap experiments provides data at the scale of individual breeding populations and their migration patterns to and from ponds. Larval density studies utilizing replicate enclosures evaluate the impact of within pond density versus variability of habitat quality across ponds. This analysis provides a bioassay of species performance teasing apart the presumed dominant effect of density versus variation across ponds. The results of this study indicate that physical and biotic pond scale factors have
a far greater effect on survival and fecundity than density. These results differ from the environmental consultant's evaluation of the same ponds and call into
question the current rapid assessment of pond habitat.Ph.D.Includes bibliographical references (p. 233-237)by Alexander Jacob Felso
Osteoarthritis as a disease of mechanics
No full textMechanics means relating to or caused by movement or physical forces. In this paper, I shall contend that osteoarthritis (OA) is almost always caused by increased physical forces causing damage to a joint. While examples of joint injury causing OA are numerous, I shall contend that most or almost all OA is caused in part by mechanically induced injury to joint tissues. Further, once joint pathology has developed, as is the case for almost all clinical OA, pathomechanics overwhelms all other factors in causing disease progression. Treatments which correct the pathomechanics have long lasting favorable effects on pain and joint function compared with treatments that suppress inflammation which have only temporary effects. I shall lastly contend that the mechanically induced joint injury leads to variable inflammatory responses but that the role of this inflammation in worsening structural damage in an already osteoarthritic joint has not yet been proven. © 2012 Osteoarthritis Research Society International
The association of meniscal damage with joint effusion in persons without radiographic osteoarthritis: the Framington and MOST osteoarthritis studies
No full textObjective: to assess the cross-sectional association between meniscal status and joint effusion on magnetic resonance imaging (MRI) in knees without radiographic osteoarthritis (OA).Design: knees without OA (Kellgren/Lawrence grade 0) from the Framingham and MOST studies were examined by MRI. Meniscal status was assessed with a score of 0–4 in the anterior horn/body/posterior horn of the medial/lateral meniscus and effusion was assessed using a score of 0–3. The odds ratios (ORs) of joint effusion in those with meniscal damage were estimated using a logistic regression model. A subanalysis was performed for knees without MRI-detected cartilage damage.Results: of 1368 knees, 296 (21.6%) showed meniscal pathology in at least one subregion. Effusion was present in 133 (44.9%) of knees with meniscal damage vs 328 (30.6%) in those without meniscal damage. The adjusted OR of effusion in a knee with meniscal damage was 1.8, 95% confidence intervals (CI) [1.4, 2.4]. The OR of effusion for the group with meniscal pathology in two compartments was 5.4, 95% CI [2.1, 14.3]. For knees without any cartilage lesions but with meniscal damage in any compartment the OR was 2.3, 95% CI [1.1, 4.5].Conclusions: knees without OA but with meniscal pathology exhibit joint effusion to a significantly higher degree than knees without meniscal damage. The association persists for knees without cartilage damage. The prevalence of effusion is further increased when present in two compartments. Concomitant occurrence of synovial activation and meniscal damage contributes to understanding the pathophysiology of early degenerative joint diseas
Smoking and osteoarthritis: a review of the evidence and its implications
No full textSummaryA number of reports including a recent publication in Osteoarthritis and Cartilage have suggested that smokers have a lower than expected prevalence of osteoarthritis (OA) than nonsmokers. We review the evidence linking smoking with OA, suggest approaches whereby the direct and indirect effects of smoking on OA might be distinguished, highlight two diseases, ulcerative colitis and Parkinson's disease, where smoking is protective, discuss mechanisms by which nicotine might act and lastly explore the association of smoking with enhanced musculoskeletal pain
Bone marrow lesions in osteoarthritis: What lies beneath
No full textOsteoarthritis (OA) is the most common joint disease in the United States, affecting more than 30 million people, and is characterized by cartilage degeneration in articulating joints. OA can be viewed as a group of overlapping disorders, which result in functional joint failure. However the precise cellular and molecular events within which lead to these clinically observable changes are neither well understood nor easily measurable. It is now clear that multiple factors, in multiple joint tissues, contribute to degeneration. Changes in subchondral bone are recognized as a hallmark of OA, but are normally associated with late-stage disease when degeneration is well established. However, early changes such as Bone Marrow Lesions (BMLs) in OA are a relatively recent discovery. BMLs are patterns from magnetic resonance images (MRI) that have been linked with pain and cartilage degeneration. Their potential utility in predicting progression, or as a target for therapy, is not yet fully understood. Here we will review the current state-of-the-art in this field under three broad headings: (1) BMLs in symptomatic OA: malalignment, joint pain and disease progression (2) biological considerations for bone-cartilage crosstalk in joint disease and (3) mechanical factors that may underlie BMLs and drive their communication with other joint tissues. Thus this review will provide insights on this topic from a clinical, biological and mechanical perspective. This article is protected by copyright. All rights reserved.Tamara Alliston, Christopher J. Hernandez, David M. Findlay, David T. Felson,
Oran D. Kenned
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