Medial meniscus
Encyclopedia
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 referred to as the internal semilunar fibrocartilage. It is a common site of injury, especially if the knee is twisted.
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
.
It is fused with the tibial collateral ligament which makes it far less mobile than the lateral meniscus. The points of attachment are relatively widely separated and, because the meniscus is wider posteriorly than anteriorly, the anterior crus is considerably thinner than the posterior crus. The greatest displacement of the meniscus is caused by external rotation, while internal rotation relaxes it.
During rotational movements of the tibia (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.
and femur
to decrease the contact area between the bones, and serves as a shock absorber
reducing the peak contact force experienced. It also reduces friction between the two bones to allow smooth movement in the knee and distribute load during movement.
) or MCL (medial collateral ligament
). A person occasionally injures the medial meniscus without harming the ligaments. Healing of the medial meniscus is generally slow. 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 meniscus may require surgical repair or removal. 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 developing osteoarthritis
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.
Fibrocartilage
White fibrocartilage consists of a mixture of white fibrous tissue and cartilaginous tissue in various proportions. It owes its flexibility and toughness to the former of these constituents, and its elasticity to the latter...
semicircular band that spans the knee joint medially, located between the medial condyle
Medial condyle of femur
The medial condyle is one of the two projections on the lower extremity of femur.The medial condyle is larger than the lateral condyle due to more weight bearing caused by the center of gravity being medial to the knee. On the posterior surface of the condyle the linea aspera turns into the...
of the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
and the medial condyle
Medial condyle of tibia
The medial condyle is the medial portion of the upper extremity of tibia.It is the site of insertion for the Semimembranosus muscle....
of the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
. It is also referred to as the internal semilunar fibrocartilage. It is a common site of injury, especially if the knee is twisted.
Structure
The meniscus attaches to the tibia via meniscotibial (coronary ligaments).Its anterior end, thin and pointed, is attached to the anterior intercondyloid fossa of the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
, in front of the anterior cruciate ligament
Anterior cruciate ligament
The anterior cruciate ligament is a cruciate ligament which is one of the four major ligaments of the human knee. In the quadruped stifle , based on its anatomical position, it is referred to as the cranial cruciate ligament.The ACL originates from deep within the notch of the distal femur...
;
Its posterior end is fixed to the posterior intercondyloid fossa
Posterior intercondyloid fossa
Posteriorly, the medial condyle and lateral condyle are separated from each other by a shallow depression, the posterior intercondyloid fossa , which gives attachment to part of the posterior cruciate ligament of the knee-joint....
of the tibia, between the attachments of the lateral meniscus
Lateral meniscus
The lateral meniscus, also called the external semilunar fibrocartilage, is a fibrocartilaginous band that spans the lateral side of the interior of the knee joint. It is one of two menisci of the knee, the other being the medial meniscus. It is nearly circular and covers a larger portion of the...
and the posterior cruciate ligament
Posterior cruciate ligament
The posterior cruciate ligament is one of the four major ligaments of the knee. It connects the posterior intercondylar area of the tibia to the medial condyle of the femur...
.
It is fused with the tibial collateral ligament which makes it far less mobile than the lateral meniscus. The points of attachment are relatively widely separated and, because the meniscus is wider posteriorly than anteriorly, the anterior crus is considerably thinner than the posterior crus. The greatest displacement of the meniscus is caused by external rotation, while internal rotation relaxes it.
During rotational movements of the tibia (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.
Function
The medial meniscus separates the tibiaTibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
and femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
to decrease the contact area between the bones, and serves as a shock absorber
Shock absorber
A shock absorber is a mechanical device designed to smooth out or damp shock impulse, and dissipate kinetic energy. It is a type of dashpot.-Nomenclature:...
reducing the peak contact force experienced. It also reduces friction between the two bones to allow smooth movement in the knee and distribute load during movement.
Injury
Acute injury to the medial meniscus fairly often accompanies an injury to the ACL (anterior cruciate ligamentAnterior cruciate ligament
The anterior cruciate ligament is a cruciate ligament which is one of the four major ligaments of the human knee. In the quadruped stifle , based on its anatomical position, it is referred to as the cranial cruciate ligament.The ACL originates from deep within the notch of the distal femur...
) or MCL (medial collateral ligament
Medial collateral ligament
The medial collateral ligament of the knee is one of the four major ligaments of the knee. It is on the medial side of the knee joint in humans and other primates. It is also known as the tibial collateral ligament, or abbreviated as the MCL.- Structure :It is a broad, flat, membranous band,...
). A person occasionally injures the medial meniscus without harming the ligaments. Healing of the medial meniscus is generally slow. 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 meniscus may require surgical repair or removal. 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 developing osteoarthritis
Osteoarthritis
Osteoarthritis also known as degenerative arthritis or degenerative joint disease, is a group of mechanical abnormalities involving degradation of joints, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking, and sometimes an effusion...
in the knee later in life.
More chronic injury occurs with osteoarthritis
Osteoarthritis
Osteoarthritis also known as degenerative arthritis or degenerative joint disease, is a group of mechanical abnormalities involving degradation of joints, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking, and sometimes an effusion...
, made worse by obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
and high-impact activity. The medial meniscus and the medial compartment are more commonly affected than the lateral compartment.
See also
- meniscusMeniscus (anatomy)In anatomy, a meniscus is a crescent-shaped fibrocartilaginous structure that, in contrast to articular disks, only partly divides a joint cavity. In humans it is present in the knee, acromioclavicular, sternoclavicular, and temporomandibular joints; in other organisms they may be present in other...
- Tear of meniscusTear of meniscusIn sports and orthopedics, a tear of a meniscus is a rupturing of one or more of the fibrocartilage strips in the knee called menisci. When doctors and patients refer to "torn cartilage" in the knee, they actually may be referring to an injury to a meniscus at the top of one of the tibiae. Menisci...
- cartilageCartilageCartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
- unhappy triadUnhappy triadAn unhappy triad is an injury to the anterior cruciate ligament, medial collateral ligament, and the meniscus. The triad refers to a complete or partial tear of the anterior cruciate ligament, medial collateral ligament, and the meniscus...
- meniscal cartilage replacement therapyMeniscal Cartilage Replacement TherapyThe meniscus is a C-shaped piece of fibrocartilage located at the peripheral aspect of the knee joint that offers lubrication and nutrition to the joint. Each knee has two menisci, medial and lateral, whose purpose is to provide space between the tibia and the femur, preventing friction and...