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Joint Stiffness
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
This chapter summarized attempts to quantify the symptom of stiffness in arthritis. It is clear that stiffness is not a straightforward symptom amenable to quantification by biomechanical devices. The sensation of stiffness results from receptors in many structures, both articular (in the joint capsule) and periarticular (ligaments), and in the tendons and muscles supplying these joints. Such peripheral stimuli may be modified, on their way to cortical appreciation, by altered synaptic activity at both the ascending and descending spinal levels. However, preliminary investigations suggest that mechanical perception thresholds are normal in rheumatoid arthritis. Other factors are worth consideration. Some patients may confuse pain with stiffness. Patients may also be complaining of limitation of range of movement in addition to increased resistance to movement. Third, arthrographic investigation of distal joint rheology may be encumbered by proximal structures, such as the muscles and tendons. The investigation of joint stiffness in isolation from muscles must be the direction of future research in this area.
The locomotor system
Published in Peter Kopelman, Dame Jane Dacre, Handbook of Clinical Skills, 2019
Peter Kopelman, Dame Jane Dacre
Stiffness Patients with locomotor system problems often complain of stiffness. This is an inability to get the joints moving again after a period of rest. In inflammatory conditions, this stiffness is much worse in the mornings and gradually wears off over a period of 1 or 2 hours. The length of time that the stiffness lasts is related to the severity of the inflammation. Patients with degenerative change also have stiffness, but the stiffness is related to inactivity, and tends to come on when sitting down for a period of 10 minutes or longer. It is sometimes called gelling.
Physics
Published in Peter R Hoskins, Kevin Martin, Abigail Thrush, Diagnostic Ultrasound, 2019
Kevin Martin, Kumar V Ramnarine
Stiffness is a measure of how well a material resists being deformed when it is squeezed. This is given by the pressure required to change its thickness by a given fraction. The pressure or stress (force per unit area) applied to the material is measured in pascal. The fractional change in thickness, or strain, is the ratio of the actual change in thickness to the original thickness of the sample. As strain is a ratio, it has no units of measurement. Hence the stiffness k, which is the ratio of stress to strain, is measured in units of pascal. Further details of stiffness can be found in Chapter 14.
Glaucoma – ‘A Stiff Eye in a Stiff Body’
Published in Current Eye Research, 2023
Sarah Powell, Mustapha Irnaten, Colm O’Brien
At a cellular level, the ECM plays a critical role in aging, stiffness and their downstream pathological consequences. Biologically, stiffness is defined as the ability of a tissue to resist deformation.62 The ECM, an extremely complex yet highly organized structure under constant tight regulatory control, provides a great deal of support-both biochemically and biomechanically- to cellular tissues and also acts as a substrate for cellular processes such as adhesion, differentiation and migration.63 The ECM is fundamentally composed of water, an array of fibrous proteins including collagen, vitronectin and fibronectin, proteoglycans, glycosaminoglycans and polysaccharides.64 Under normal circumstances, dynamic remodeling of ECM following cellular insult or injury functions as a protective cellular mechanism, one that restores tissue function and integrity. The level of ECM stiffness thus plays a central effector role in cellular behaviour.63,65
In Vivo Biomechanical Changes Associated With Keratoconus Progression
Published in Current Eye Research, 2022
Prema Padmanabhan, Bernardo T. Lopes, Ashkan Eliasy, Ahmed Abass, Ahmed Elsheikh
The progressive nature of KC is arguably its grimmest aspect. As visual acuity continuously deteriorates, the quality of life is gradually affected.7 In a recent meta-analysis of KC natural progression conducted by Ferdi et al. younger age and steeper baseline KMax were the main variables associated with the disease progression.12 The authors suggested that patients aged below 17 years and with KMax steeper than 55 D undergo close follow-up with a lower threshold for CXL than other patient groups. This suggestion is in line with the pathophysiology of the disease, in which low biomechanical stiffness (experienced in young age and advanced disease stages) is an underlying cause of its natural progression.6 Despite this fact, previous attempts to classify disease severity and its progression often relied on morphologic and optic aspects of the disease without direct consideration of the biomechanical aspect.16,20,21 This study seeks to assess the biomechanics of the keratoconic cornea and present in vivo evidence of its deterioration with disease progression.
Longitudinal evaluation of liver stiffness and outcomes in patients with chronic hepatitis C before and after short- and long-term IFN-free antiviral treatment
Published in Current Medical Research and Opinion, 2020
Cristina Stasi, Sinan Sadalla, Eleonora Carradori, Monica Monti, Luisa Petraccia, Francesco Madia, Laura Gragnani, Anna Linda Zignego
Due to the recent introduction of DAAs, few studies have been conducted for the longitudinal evaluation of liver fibrosis and outcomes in patients with chronic hepatitis C at baseline, and after a short- and long-term follow-up after IFN-free antiviral treatment. This study demonstrated that a significant reduction in stiffness values was observed at different time points during treatment for periods of time ranging from 1 year to a maximum of 2 years when compared to pre-treatment stiffness values. On the contrary, at the EOT, only AST and ALT values were significantly different. This confirms a substantial reduction in necroinflammation at the end of treatment and a certain degree of fibrosis regression after the EOT. According to our results, Bachofner et al.17 showed a rapid decrease in liver stiffness values that was in concordance with regression of the validated fibrosis scores FIB-4 and APRI, suggesting an investigation into whether this indicates a real regression of fibrosis or merely a resolution of chronic liver inflammation.