Meniscus - Knee & Sports

Function
Force transmission the meniscus functions to optimize force transmission across the knee. It does this by increasing congruency increases contact area leads to decreased point loading shock-absorption the meniscus is more elastic than articular cartilage, and therefore absorbs shock transmits 50% weight-bearing load in extension, 85% in flexion Stability the meniscus deepens tibial surface and acts as secondary stabilizer medial meniscus posterior horn of medial meniscus is the main secondary stabilizer to anterior translation lateral meniscus is less stabilizing and has 2X the excursion of the medial meniscus the menisci become primary stabilizers in the ACL-deficient knee
Composition
Made of fibroelastic cartilage interlacing network of collagen, proteoglycan, glycoproteins, and cellular elements composed of 65-75% water Collagen 90 % Type I collagen Fibers composed of two types of fibers which allow the meniscus to expand under compressive forces and increase contact area of the joint radial longitudinal (circumferential) help dissipate hoop stresses vertical mattress captures
Anatomy
Gross Shape medial meniscus C-shaped with triangular cross section avarage width of 9 to 10mm average thickness of 3 to 5mm lateral meniscus is more circular (the horns are closer together and approximate the ACL) covers a larger portion of the articular surface average width is 10 to 12mm average thickness is 4 to 5mm Attachment transverse (intermeniscal) ligament connects the medial and lateral meniscus anteriorly coronary ligaments connects the meniscus peripherally medial meniscus has less mobility with more rigid peripheral fixation than the lateral meniscus meniscofemoral ligament connects the meniscus into the substance of the PCL originate from the posterior horn of the lateral meniscus and has two components Humphrey ligament (anterior) Ligament of Wrisberg (posterior) Blood supply middle genicular artery supply to posterior horns medial inferior genicular artery supplies peripheral 20-30% of medial meniscus lateral inferior genicular artery supplies peripheral 10-25% of lateral meniscus central 75% receive nutrition through diffusion Innervation peripheral two-thirds innervated by Type I and II nerve endings posterior horns have highest concentration of mechanoreceptors
Injury & Healing potential
See topic Meniscal Pathology Tears in peripheral 25% red zone can heal via fibrocartilage scar formation fibrochondrocyte is cell responsible for healing peripheral tears < 4 mm have best healing potential Tears of central 75% have limited or no intrinsic healing ability