Short cracks in knee meniscus tissue cause strain concentrations, but do not reduce ultimate stress, in single-cycle uniaxial tension

Santare

Elliott

2023

Preprint

Self Cite

Load-induced volume change is an important aspect of knee meniscus function because volume loss creates fluid pressure, which minimizes friction and helps support compressive loads. The knee meniscus is unusual amongst cartilaginous tissues in that it is loaded not only in axial compression, but also in circumferential tension between its tibial attachments. Despite the physiologic importance of the knee meniscus' tensile properties, its volumetric strain in tension has never been directly measured, and predictions of volume strain in the scientific literature are inconsistent. In this study, we apply uniaxial tension to bovine knee meniscus and use biplanar imaging to directly observe the resulting 3D volume change and unloaded recovery, revealing that tension causes volumetric contraction. Compression is already known to also cause contraction; therefore, all major physiologic loads compress and pressurize the meniscus, inducing fluid outflow. Although passive unloaded recovery is often described as slow relative to loaded loss, here we show that at physiologic strains the volume recovery rate in the meniscus upon unloading is faster than the rate of volume loss. These measurements of volumetric strain are an important step towards a complete theory of knee meniscus fluid flow and load support.

Section: Methodsmentioning

confidence: 99%

Volume loss and recovery in bovine knee meniscus loaded in circumferential tension

Santare

Elliott

2023

Preprint

Self Cite

“…In both directions, a thickness of 350 μm was chosen so as to obtain more than one section per donor and to improve sample gripping within clamps. Each of these multiple sections was treated as a separate sample given that intermeniscus variability is similar to intrameniscus variability 20 . All samples were stored in 1X PBS for 24 to 48 hours at 4°C prior to testing.…”

Section: Methodsmentioning

confidence: 99%

“…Intact and defect linear moduli are presented as mean with 95% confidence interval. Change in properties due to the defect was calculated relative to the average mechanical properties of each age (change = [defected sample − intact mean for sample's age]/intact mean for sample's age), given that intermeniscus variability is similar to intrameniscus variability for sections such as these 20 . Immediately following testing, a subset (n = 4, fetal; n = 7, juvenile; and n = 7, adult) pooled for correlative analysis of notch defected samples were embedded in OCT, cryosectioned to 35 μm thickness in the radial plane (within 3 mm of the defect) and SHG image analysis was used to quantify the local RTF network.…”

Section: Methodsmentioning

confidence: 99%

“…Each of these multiple sections was treated as a separate sample given that intermeniscus variability is similar to intrameniscus variability. 20 All samples were stored in 1X PBS for 24 to 48 hours at 4°C prior to testing. Immediately prior to testing, sections were further trimmed to a dogbone shape ( Figure 1D).…”

Section: Menisci Collection and Sample Preparation-functional Assaysmentioning

confidence: 99%

See 1 more Smart Citation

Structure, function, and defect tolerance with maturation of the radial tie fiber network in the knee meniscus

Bansal

Journal Orthopaedic Research

Keah

et al. 2020

Self Cite

The knee menisci are comprised of two orthogonal collagenous networks—circumferential and radial—that combine to enable efficient load bearing by the tissue in adults. Here, we assessed how the structural and functional characteristics of these networks developed over the course of skeletal maturation and determined the role of these fiber networks in defect tolerance with tissue injury. Imaging of the radial tie fiber (RTF) collagen structure in medial bovine menisci from fetal, juvenile, and adult specimens showed increasing heterogeneity, anisotropy, thickness, and density with skeletal development. The mechanical analysis showed that the tensile modulus in the radial direction did not change with skeletal development, though the resilience (in the radial direction) increased and the tolerance to defects in the circumferential direction decreased, in adult compared to fetal tissues. This loss of defect tolerance correlated with increased order in the RTF network in adult tissue. These data provide new insights into the role of the radial fiber network in meniscus function, will lead to improved clinical decision‐making in the presence of a tear and may improve engineering efforts to reproduce this critical load‐bearing structure in the knee.

“…The underlying data for all results is available, hosted on the Open Science Framework, under a CC-BY license (Peloquin 2018).…”

Section: Data Accessibility Statementmentioning

confidence: 99%

Short cracks in knee meniscus tissue cause strain concentrations, but do not reduce ultimate stress, in single-cycle uniaxial tension

Santare

Elliott

2018

Preprint

Self Cite

Tears are central to knee meniscus pathology. From a mechanical perspective, meniscus tears are a type of crack-like defect. In many materials, cracks create stress concentrations that cause failure by fracture and thereby reduce the material's effective strength. It is currently unknown whether the meniscus is vulnerable to fracture. If meniscus tears cause fracture, this would have significant repercussions for management of meniscus pathology. The objective of this study was to determine if short crack-like defects in the meniscus, representing short meniscus tears, cause fracture and, by unloading the cut region, stress concentrations. Failure stress was compared between cracked and control specimens to determine if fracture occurred. Strain concentrations near the crack tip were quantified using digital image correlation (DIC) and used as an indicator of stress concentrations. The presence of cracks did not affect the meniscus' failure stress (effect < 0.86 s.d.; β = 0.2), and cracks almost always became blunt or were deflected along fascicle boundaries instead of growing. However, significant strain concentrations were observed near the crack tip even at low applied stress. Although the maintenance of macroscopic failure stress indicates low risk of failure for short meniscus tears, long-term crack growth and failure, such as by accumulation of tissue or cell damage, may still occur due to the strain concentrations.