Medial meniscus

The medial meniscus (internal semilunar fibrocartilage) is nearly semicircular in form, a little elongated from before backward, and broader behind than in front;

Attachments
Its anterior end, thin and pointed, is attached to the anterior intercondyloid fossa of the tibia, in front of the anterior cruciate ligament;

Its posterior end is fixed to the posterior intercondyloid fossa of the tibia, between the attachments of the lateral meniscus and the posterior cruciate ligament.

Function
The medial meniscus, along with the lateral meniscus, separate the tibia and femur.

They serve as shock absorbers in the knee and increase the contact area between the tibia and femur, reducing the peak contact force experienced.

They also reduce friction between the two bones to allow smooth movement in the knee.

Injury
Acute injury to the medial meniscus fairly often accompanies an injury to the ACL or anterior cruciate ligament. As with much cartilage, the medial meniscus is slow to heal. Damage to the outer 1/3 of the meniscus will often fully heal, but the inner 2/3 of the medial meniscus has a limited blood supply and thus limited healing ability. Large tears to the outer portions of the meniscus may be repaired surgically. If the meniscus has to be removed (menisectomy) because of injury (either because it cannot heal or because the damage is too severe) the patient has an increased risk of arthritis in the knee later in life.

More chronic injury occurs with osteoarthritis, made worse by obesity and high-impact activity. The medial meniscus and the medial compartment are more commonly affected than the lateral compartment.