The Meniscus: Basic Science

The menisci are semilunar discs of fibrocartilaginous tissue which play critical roles in knee joint biomechanics [1]. Despite, it has been described in the past as nearly useless with perhaps some minor roles on joint nutrition and stabilization [2]. These complex structures are primarily composed of an interlacing network of collagen fibers (predominantly type I collagen) interposed with cells, and an extracellular matrix (ECM) of proteoglycans and glycoproteins. Menisci are placed within each knee, between the correspondent lateral and medial femoral condyles and tibial plateaux. It has been now recognized that its removal determines deleterious joint consequences, particularly on the long term [3]. Due to the pivotal role of meniscus in maintaining knee homeostasis and proper joint functioning/stability, novel regenerative treatments have been attempted to develop as an alternative to traditional repair procedures or meniscectomy. The basic science knowledge concerning human meniscus require re-appreciation given the overturn on therapeutic approach, i.e. from meniscectomy to preservation or substitution; and the nearly universal arthroscopic surgical approach opposing to open surgery. The biological characterization of this tissue, although not yet completely accomplished, has evolved significantly in the last few years. This is true concerning recognition of different cellular populations, understanding its ultrastructure [4], cells and extracellular matrix segmental distributions, biomechanical properties, biologic interactions and mechanism for triggering the response to injury.