The medial meniscus is a fibrocartilage semicircular band that spans the knee joint medially, located between the medial condyle of the femur and the medial condyle of the tibia.
It is also known as the internal semilunar fibrocartilage.
The medial meniscus has a crescent shape, while the lateral meniscus is more circular.
The transverse ligament connects the anterior aspects of both menisci.
It is a common site of injury, especially if the knee is twisted.
The medial meniscus and the medial compartment are more commonly affected than the lateral compartment.
The medial meniscus attaches to the tibia via coronary ligaments.
The medial meniscus anterior end is thin and pointed, and attaches to the anterior intercondyloid fossa of the tibia, in front of the anterior cruciate ligament;
The medial meniscus posterior end is fixed to the posterior intercondyloid fossa of the tibia, between the attachments of the lateral meniscus and the posterior cruciate ligament.
The medial meniscus is fused with the tibial collateral ligament, making it less mobile than the lateral meniscus.
The meniscus is wider posteriorly than anteriorly, and the anterior crus is considerably thinner than the posterior crus.
Its greatest displacement is caused by external rotation, while internal rotation relaxes it.
During rotational movement with the knee flexed 90 degrees, the medial meniscus remains relatively fixed while the lateral part of the lateral meniscus is displaced across the tibial condyle below.
The medial meniscus separates the tibia and femur to decrease the contact area between the bones, serves as a shock absorber reducing the peak contact force experienced, and reduces friction between the two bones to allow smooth movement in the knee and distribute load during movement.
An acute injury to the medial meniscus, frequently is accompanied by an injury to the ACL (anterior cruciate ligament) or MCL (medial collateral ligament).
Healing of the medial meniscus is generally not possible unless the patient is very young, <15 years old.
The outer third of the meniscus has the best healing potential because of the blood supply.
The outer edge of the meniscus is referred to as the “red zone” because it is highly vascularized, receiving nutrients and support needed for successful recovery.
The inner two thirds of the medial meniscus has a limited blood supply and thus limited healing ability.
The inner two-thirds of the meniscus are called the “white zone., and is not highly vascularized.
The inner two-thirds of the meniscus receives its nourishment from only the synovial fluid via diffusion.
Large tears to the meniscus may require surgical repair or removal.
If the meniscus has to be removed, there is an increased risk of developing osteoarthritis in the knee later in life.
Meniscus transplant options are available for young patients with normal knee alignment.
Chronic injury of the median meniscus may occur with osteoarthritis, and is made worse by obesity and high-impact activity.
Tears are the primary diagnosis for >29% of patients treated with an arthroscopic procedure for osteoarthritis of the knee.