A meniscus (: menisci or meniscuses) is a crescent-shaped

fibrocartilaginous Fibrocartilage consists of a mixture of white fibrous tissue and Cartilage, cartilaginous tissue in various proportions. It owes its inflexibility and toughness to the former of these constituents, and its Elasticity (physics), elasticity to the ...

anatomical Anatomy () is the branch of morphology concerned with the study of the internal structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old scien ...

structure that, in contrast to an

articular disc The articular disc (or disk) is a thin, oval plate of fibrocartilage present in several joints which separates synovial cavities. This separation of the cavity space allows for separate movements to occur in each space. The presence of an articul ...

, only partly divides a joint cavity.Platzer (2004), p 208 In

human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

s, they are present in the

knee In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the hu ...

wrist In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal ...

, acromioclavicular, sternoclavicular, and

temporomandibular joint In anatomy, the temporomandibular joints (TMJ) are the two joints connecting the jawbone to the skull. It is a bilateral Synovial joint, synovial articulation between the temporal bone of the skull above and the condylar process of mandible be ...

s; in other animals they may be present in other joints. Generally, the term "meniscus" is used to refer to the

cartilage Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

of the

, either to the

lateral Lateral is a geometric term of location which may also refer to: Biology and healthcare * Lateral (anatomy), a term of location meaning "towards the side" * Lateral cricoarytenoid muscle, an intrinsic muscle of the larynx * Lateral release ( ...

or medial meniscus. Both are

cartilaginous Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

tissues that provide structural integrity to the knee when it undergoes tension and torsion. The menisci are also known as "semi-lunar" cartilages, referring to their half-moon, crescent shape. The term "meniscus" is from the Ancient Greek word (), meaning "crescent".

Structure

The menisci of the knee are two pads of

tissue which serve to disperse friction in the

joint between the lower leg (

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

) and the thigh (

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

). They are concave on the top and flat on the bottom, articulating with the tibia. They are attached to the small depressions ( fossae) between the condyles of the tibia (intercondyloid fossa), and towards the center from the rim of the bone, they are unattached and their shape narrows to a thin shelf.Gray's (1918), 7b The blood flow of the meniscus is from the periphery (outside) to the central meniscus. Blood flow decreases with age and the central meniscus is avascular by adulthood, which slows healing. Menisci show low-intensity on MRI images.

Function

The menisci act to disperse the weight of the body and reduce friction during movement. Since the condyles of the femur and tibia meet at one point (which changes during

flexion Motion, the process of movement, is described using specific anatomical terminology, anatomical terms. Motion includes movement of Organ (anatomy), organs, joints, Limb (anatomy), limbs, and specific sections of the body. The terminology used de ...

and extension), the menisci spread the load of the body's weight. This differs from

sesamoid bone In anatomy, a sesamoid bone () is a bone embedded within a tendon or a muscle. Its name is derived from the Greek word for 'sesame seed', indicating the small size of most sesamoids. Often, these bones form in response to strain, or can be presen ...

s, which are made of

osseous tissue A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provi ...

and whose function primarily is to protect the nearby tendon and to increase its mechanical effect.

Clinical significance

Injury

sport Sport is a physical activity or game, often Competition, competitive and organization, organized, that maintains or improves physical ability and skills. Sport may provide enjoyment to participants and entertainment to spectators. The numbe ...

s and

orthopedics Orthopedic surgery or orthopedics (American and British English spelling differences, alternative spelling orthopaedics) is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgic ...

, people sometimes speak of "torn cartilage" and will actually be referring to an injury to one of the menisci. There are two general types of meniscus injuries: acute tears which are often the result of trauma or a sports injury and chronic or wear-and-tear type tears. Acute tears have many different shapes (vertical, horizontal, radial, oblique, complex) and sizes. They are often treated with surgical repair depending upon the patient's age as they rarely heal on their own. Chronic tears are treated symptomatically: physical therapy with or without the addition of injections and anti-inflammatory medications. If the tear causes continued pain, swelling, or knee dysfunction, then the tear can be removed or repaired surgically. The

unhappy triad The unhappy triad, also known as a blown knee among other names, is an knee injury, injury to the anterior cruciate ligament, medial collateral ligament, and meniscus (anatomy), meniscus. Analysis during the 1990s indicated that this 'classic' O' ...

is a set of commonly co-occurring knee injuries which includes injury to the medial meniscus.

Conservative management

Conservative management is often considered first for a smaller or chronic tear that does not appear to require surgical repair. It consists of activity modification or

physical therapy Physical therapy (PT), also known as physiotherapy, is a healthcare profession, as well as the care provided by physical therapists who promote, maintain, or restore health through patient education, physical intervention, disease preventio ...

to strengthen and increase the

range of motion Range of motion (or ROM) is the linear or angular distance that a moving object may normally travel while properly attached to another. In biomechanics and strength training, ROM refers to the angular distance and direction a joint can move be ...

Surgical treatment

Two surgeries of the meniscus are most common. Depending on the type and location of the tear, the patient's age, and physician's preference, injured menisci are usually either repaired or removed, in part or completely (meniscectomy). Each has its advantages and disadvantages. Many studies show the meniscus serves a purpose and therefore doctors will attempt to repair it when possible. However, the meniscus has poor blood supply, and, therefore, healing can be difficult. Traditionally it was thought that if there is no chance of healing, then it is best to remove the damaged and non-functional meniscus, although at least one study has shown that there is little significance if a meniscectomy is done for a degenerative tear. However, resuming high-intensity activities may be impossible without surgery as the tear may flap around, causing the knee to lock. A 2017 clinical practice guideline strongly recommends against surgery in nearly all patients with degenerative knee disease.

Etymology

The term meniscus derives from

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

, meaning "crescent". The word was used for curved things in general, such as a necklace or a line of battle.''Lexicon of Orthopaedic Etymology'', p. 199

Gallery

Image:Braus 1921 284.png Image:Braus 1921 285.png

References

;Sources * * * * * {{DEFAULTSORT:Meniscus (Anatomy) Joints