Current concepts on structure–function relationships in the menisci

Abstract

The menisci are intricately organized structures that perform many tasks in the knee. We review their structure and function and introduce new data about their tibial and femoral surfaces. As the femur and tibia approach each other when the knee is bearing load, circumferential tension develops in the menisci, enabling the transmission of compressive load between the femoral and tibial cartilage layers. A low shear modulus is necessary for the tissue to adapt its shape to the changing radius of the femur as that bone moves relative to the tibia during joint articulation. The organization of the meniscus facilitates its functions. In the outer region of the menisci, intertwined collagen fibrils, fibers, and fascicles with predominantly circumferential orientation are prevalent; these structures are held together by radial tie fibers and sheets. Toward the inner portion of the menisci, there is more proteoglycan and the structure becomes more cartilage-like. The transition between these structural forms is gradual and seamless. The flexible roots, required for rigid body motion of the menisci, meld with both the tibia and the outer portion of the menisci to maintain continuity for resistance to the circumferential tension. Our new data demonstrate that the femoral and tibial surfaces of the menisci are structurally analogous to the surfaces of articular cartilage, enabling consistent modes of lubrication and load transfer to occur at the interfacing surfaces throughout motion. The structure and function of the menisci are thus shown to be strongly related to one another: form clearly complements function.

Meniscus beyond mechanics: Using biology to advance our understanding of meniscus injury and treatment

“…The C-shaped structure of the meniscus tissue is precisely well designed to perform multiple mechanical functions. Andrews and colleagues provide an overview of the structural and mechanical properties of meniscus and in particular highlight the observations that the organization of the meniscus tissue follows the mechanical function of the tissue (1). Meniscus injury and pathology disrupt not only the critical biomechanical function of the tissue but lead to biological changes in the meniscus as well.…”

The Meniscus Tear: A Review of Stem Cell Therapies

“…Within the meniscus fibrils, fibers, and fascicles are arranged in diverse patterns depending on the region of tissue [18]. The innermost region consists of small unorganized woven radial collagen fibrils with a structure similar to that of cartilage [19,20], with greater proteoglycan content.…”

“…The outer region consists of intertwined collagen fibrils in a circumferential orientation with radially oriented three-dimensional arrays of fibers known as "tie-fibers" (Figure 2). They lie perpendicular to the circumferential collagen fibers and originate from the joint capsule creating a complex honeycomb network [18,21]. The root attachments of the meniscus to the tibia are more ligamentous-like structures with a fibrocartilaginous enthesis [22].…”

Coculture of meniscus cells and mesenchymal stem cells in simulated microgravity

“… 1 They primarily serve as mechanical load distributors within the knee joint. 2 Traumatic tears in the avascular region of the tissue are common and do not heal. 1 Treatment options for these tears are currently limited to partial meniscectomy.…”