MRI anatomy of the meniscal roots of knee

Objective To summarize the MRI anatomy of meniscal roots, and to determine the delimitation between meniscal main body and roots. Methods Knee of a male adult patient with amputation due to arteriosclerosis of lower extremity MR images of normal meniscal roots of 24 patients confirmed by arthroscopy and 1 fresh knee joint specimen were collected from October 2012 to February 2014. MRI anatomy of the meniscal roots of knee were studied prospectively. The dimension, courses, insertion sites and signals of meniscal roots were analyzed. Length, height, width and course angles of the meniscal roots were measured. To determine the delimitation of meniscal main body and root in the fresh knee joint specimen, then the specimen was studied with MR exam. Results The posterior root of medial meniscus inclined downward, which were attached to the posterior intercondylar area. Its comblike signal was slightly higher than that of meniscal main body. The posterior root of lateral meniscus run at the intercondylar eminence was obviously longer than that of medial meniscus, and attached to lateral surface of the medial intercondylar eminence. Its signal is similar to that of meniscal main body. The anterior root of medial meniscus attached to the most anterior border of the anterior tibia intercondylar area, and its signal was lower or slightly lower. The anterior root of lateral meniscus coursed downward and backward, and attached to the anterior intercondylar area and the surface of the bone sloping outwards and inferiorly. Its signal was slightly hyperintense and comblike. MR images of fresh knee joint specimen and the delimitation marker of meniscal main body and root were clear. The longest part was the posterior root of lateral meniscus, which was (15.74±2.03)mm, the shortest part was the posterior root of medial meniscus, which was (7.88±1.57)mm. The posterior root of lateral meniscus had the maximum course angle, which was 34.00°±9.24°. Conclusions The MR features of the four meniscal roots are different from each other. MR imaging is a relatively good method to show the meniscal roots and display clearly the features of the dimensions, courses, signal, and insertion sites of meniscal roots. Key words: Knee joint; Meniscus, tibial; Magnetic resonance imaging; Anatomy