Aim of the study: To study the morphological and morphometric study of the menisci of the knee joint and its clinical significance. Objectives: To estimate the incidence of different shapes of the medial and lateral menisci and the incidence of discoid meniscus. To evaluate the morphometric variations in the menisci. Materials and Methods: The study was carried out over a period of three years in the Department of Anatomy, Sri Ramachandra Medical College and Research Institute, Sri Ramachandra University, Chennai. Materials: The following materials were used for the study: Human adult knee joints, available in the Anatomy dissection hall, were used for the present study. The study includes 116 menisci from 58 knee joints of adult cadavers. Among them, 31 were right-sided and 27 were left-sided isolated lower limbs. Methods 1.Morphological Study: After the dissection of the skin and muscles, the approaches to the menisci were performed, opening anteriorly by a longitudinal incision on each side of the joint capsule, cutting the patellar ligament and the collateral ligaments transversely. In order to expose the menisci clearly, the joint capsule and the intra-articular ligaments were cut and the condyles were circumferentially detached from their soft tissue attachments and removed, exposing the tibial plateau. All dissections were performed in a systematic fashion and the data were recorded on a standardized collection sheet. Morphological variants of the shapes of the menisci were macroscopically noted and classified. The medial menisci (MM) were sub-grouped as sickle shaped, sided U shaped, sided V-shaped, crescent-shaped and C-shaped. The lateral meniscus (LM) was sub-grouped as crescent (semilunar)-shaped, C-shaped and discoid-shaped. When the meniscus covers the tibial plateau circularly, the meniscus is said to be a discoid type. Menisci, which had thin anterior and posterior horns and thin bodies, were defined as crescent (semilunar)- types. Menisci, which had thin anterior, posterior horns and thick bodies, were defined as sickle-shaped types. Menicsi which resembled sided U, sided V and C were named as sided U, sided V and C shaped respectively. Menisci that showed any structural changes, such as injuries or advanced degenerative changes were excluded. 2.Morphometric Study: To measure the length of the menisci, a line was positioned from the apex of anterior horn to the apex of posterior horn of the meniscus. The distance of the line was measured with Vernier Caliper. The width of menisci was determined by establishing three points: anterior third (a), medium third (b) and posterior third (c). From each point, one line was drawn from the peripheral margin to the central margin of meniscus. The values were recorded. The thickness of the meniscus was determined using the same width points, between the top and bottom edge in outer circumference only. The data were tabulated and statistically analysed. Discussion: The present study was undertaken in 116 adult menisci from 58 adult cadaveric knee joints. Menisci were studied for a review of its morphology, morphometry and its comparison with previous studies. The main findings were: Five morphological types of menisci were determined. Out of 58 medial menisci studied, 54.6% were crescent shaped; 34.6% were V shaped;10.8% were U shaped and no discoid medial menisci were found. Out of 58 lateral menisci studied, 41.6% were crescent shaped; 56.4% were C shaped; 2% discoid lateral menisci were found. Morphometry revealed the following results: The length of lateral meniscus is smaller than that of the medial meniscus; the width of the lateral meniscus is more than that of the medial meniscus; the medial meniscus is thicker when compared to lateral meniscus in both the left and right side knee. Difference in shape and size of menisci in the same knee as well as with different knees of different cadavers were observed. The obtained results presented variations regarding some parameters when compared to the previous studies. Conclusion: The present study will provide support to the meniscal anatomy, concerning the surgical procedures and arthroscopy of the knee joint. The study has provided additional information on different shapes of the medial and lateral meniscus with contribution to a better delineation of meniscal anatomy and implications in regard to allograft meniscus transplantation. Therefore, health professionals that work with the treatment of meniscal injuries should be aware of the possible anatomical variations that may exist in the meniscus facilitating the rehabilitation process.
