Meniscus (anatomy)

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Meniscus
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Head of right tibia seen from above, showing menisci and attachments of ligaments
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Left knee-joint from behind, showing interior ligaments
Details
Identifiers
Latin meniscus
Greek μηνίσκος ("meniskos")
MeSH D000072600
TA98 A03.0.00.033
TA2 1544
Anatomical terminology

A meniscus (pl.: menisci or meniscuses) is a crescent-shaped fibrocartilaginous anatomical structure that, in contrast to an articular disc, only partly divides a joint cavity. [1] In humans, they are present in the knee, wrist, acromioclavicular, sternoclavicular, and temporomandibular joints; [2] in other animals they may be present in other joints.

Contents

Generally, the term "meniscus" is used to refer to the cartilage of the knee, either to the lateral or medial meniscus. Both are cartilaginous 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 μηνίσκος (meniskos), meaning "crescent". [3]

Structure

The menisci of the knee are two pads of fibrocartilaginous tissue which serve to disperse friction in the knee joint between the lower leg (tibia) and the thigh (femur). 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 they are unattached and their shape narrows to a thin shelf. [4] 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. [5]

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 and extension), the menisci spread the load of the body's weight. [6] This differs from sesamoid bones, which are made of osseous tissue and whose function primarily is to protect the nearby tendon and to increase its mechanical effect.

Clinical significance

Injury

Scar from partial left menisectomy in 1980 (c. 30 years before photo); more recent surgery leaves smaller scars. MenisectomyScar1980.jpg
Scar from partial left menisectomy in 1980 (c. 30 years before photo); more recent surgery leaves smaller scars.

In sports and orthopedics, 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 that 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 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 to strengthen and increase the range of motion.[ citation needed ]

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 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. [7] 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. [8]

Etymology

The term meniscus derives from Greek μηνίσκος meniskos, meaning "crescent". The word was used for curved things in general, such as a necklace or a line of battle. [3]

See also

Related Research Articles

<span class="mw-page-title-main">Knee</span> Leg joint in primates

In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia, and one between the femur and patella. It is the largest joint in the human body. The knee is a modified hinge joint, which permits flexion and extension as well as slight internal and external rotation. The knee is vulnerable to injury and to the development of osteoarthritis.

<span class="mw-page-title-main">Arthroscopy</span> Medical procedure

Arthroscopy is a minimally invasive surgical procedure on a joint in which an examination and sometimes treatment of damage is performed using an arthroscope, an endoscope that is inserted into the joint through a small incision. Arthroscopic procedures can be performed during ACL reconstruction.

<span class="mw-page-title-main">Posterior cruciate ligament</span> One of four major ligaments of the knee

The posterior cruciate ligament (PCL) is a ligament in each knee of humans and various other animals. It works as a counterpart to the anterior cruciate ligament (ACL). It connects the posterior intercondylar area of the tibia to the medial condyle of the femur. This configuration allows the PCL to resist forces pushing the tibia posteriorly relative to the femur.

A meniscus transplant or meniscal transplant is a transplant of the meniscus of the knee, which separates the thigh bone (femur) from the lower leg bone (tibia). The worn or damaged meniscus is removed and is replaced with a new one from a donor. The meniscus to be transplanted is taken from a cadaver, and, as such, is known as an allograft. Meniscal transplantation is technically difficult, as it must be sized accurately for each person, positioned properly and secured to the tibial plateau. Its success also depends on donor compatibility, stability of the transplant, and long-term health of the underlying articular cartilage.

<span class="mw-page-title-main">Medial meniscus</span> Cartilage formation in the human knee

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. The medial meniscus has more of a crescent shape while the lateral meniscus is more circular. The anterior aspects of both menisci are connected by the transverse ligament. It is a common site of injury, especially if the knee is twisted.

<span class="mw-page-title-main">Lateral meniscus</span>

The lateral meniscus 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 articular surface than the medial. It can occasionally be injured or torn by twisting the knee or applying direct force, as seen in contact sports.

The knee examination, in medicine and physiotherapy, is performed as part of a physical examination, or when a patient presents with knee pain or a history that suggests a pathology of the knee joint.

Articular cartilage, most notably that which is found in the knee joint, is generally characterized by very low friction, high wear resistance, and poor regenerative qualities. It is responsible for much of the compressive resistance and load bearing qualities of the knee joint and, without it, walking is painful to impossible. Osteoarthritis is a common condition of cartilage failure that can lead to limited range of motion, bone damage and invariably, pain. Due to a combination of acute stress and chronic fatigue, osteoarthritis directly manifests itself in a wearing away of the articular surface and, in extreme cases, bone can be exposed in the joint. Some additional examples of cartilage failure mechanisms include cellular matrix linkage rupture, chondrocyte protein synthesis inhibition, and chondrocyte apoptosis. There are several different repair options available for cartilage damage or failure.

<span class="mw-page-title-main">Meniscal cartilage replacement therapy</span>

Meniscal cartilage replacement therapy is surgical replacement of the meniscus of the knee as a treatment for where the meniscus is so damaged that it would otherwise need to be removed.

<span class="mw-page-title-main">Anterior cruciate ligament injury</span> Ligament injury near the knee

An anterior cruciate ligament injury occurs when the anterior cruciate ligament (ACL) is either stretched, partially torn, or completely torn. The most common injury is a complete tear. Symptoms include pain, an audible cracking sound during injury, instability of the knee, and joint swelling. Swelling generally appears within a couple of hours. In approximately 50% of cases, other structures of the knee such as surrounding ligaments, cartilage, or meniscus are damaged.

<span class="mw-page-title-main">Unhappy triad</span> Medical condition of the knee

The unhappy triad, also known as a blown knee among other names, is an injury to the anterior cruciate ligament, medial collateral ligament, and meniscus. Analysis during the 1990s indicated that this 'classic' O'Donoghue triad is actually an unusual clinical entity among athletes with knee injuries. Some authors mistakenly believe that in this type of injury, "combined anterior cruciate and medial collateral ligament disruptions that were incurred during athletic endeavors" always present with concomitant medial meniscus injury. However, the 1990 analysis showed that lateral meniscus tears are more common than medial meniscus tears in conjunction with sprains of the ACL.

<span class="mw-page-title-main">Microfracture surgery</span> Cartilage repair technique

Microfracture surgery is an articular cartilage repair surgical technique that works by creating tiny fractures in the underlying bone. This causes new cartilage to develop from a so-called super-clot.

<span class="mw-page-title-main">Coronary ligament of the knee</span>

The coronary ligaments of the knee are portions of the joint capsule which connect the inferior edges of the fibrocartilaginous menisci to the periphery of the tibial plateaus.

<span class="mw-page-title-main">Meniscus tear</span> Rupturing of the fibrocartilage strips in the knee called menisci

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 can be torn during innocuous activities such as walking or squatting. They can also be torn by traumatic force encountered in sports or other forms of physical exertion. The traumatic action is most often a twisting movement at the knee while the leg is bent. In older adults, the meniscus can be damaged following prolonged 'wear and tear'. Especially acute injuries can lead to displaced tears which can cause mechanical symptoms such as clicking, catching, or locking during motion of the joint. The joint will be in pain when in use, but when there is no load, the pain goes away.

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<span class="mw-page-title-main">Discoid meniscus</span>

Discoid meniscus is a rare human anatomic variant that usually affects the lateral meniscus of the knee. Usually a person with this anomaly has no complaints; however, it may present as pain, swelling, or a snapping sound heard from the affected knee. Strong suggestive findings on magnetic resonance imaging includes a thickened meniscal body seen on more than two contiguous sagittal slices.

Kevin Robert Stone is an American physician, orthopedic surgeon, clinician, researcher, and company founder of The Stone Clinic and the Stone Research Foundation in San Francisco.

<span class="mw-page-title-main">Knee pain</span> Medical condition

Knee pain is pain in or around the knee.

Posterolateral corner injuries of the knee are injuries to a complex area formed by the interaction of multiple structures. Injuries to the posterolateral corner can be debilitating to the person and require recognition and treatment to avoid long term consequences. Injuries to the PLC often occur in combination with other ligamentous injuries to the knee; most commonly the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). As with any injury, an understanding of the anatomy and functional interactions of the posterolateral corner is important to diagnosing and treating the injury.

References

  1. ↑ Platzer (2004), p 208
  2. ↑ "Meniscus", Stedman's (27th ed.)
  3. 1 2 Lexicon of Orthopaedic Etymology, p. 199
  4. ↑ Gray's (1918), 7b
  5. ↑ Nguyen, Jie C.; De Smet, Arthur A.; Graf, Ben K.; Rosas, Humberto G. (July 2014). "MR Imaging–based Diagnosis and Classification of Meniscal Tears". RadioGraphics. 34 (4): 981–999. doi:10.1148/rg.344125202. ISSN   0271-5333. PMID   25019436.
  6. ↑ Cluett, Meniscus Tear — Torn Cartilage
  7. ↑ Sihvonen R, Paavola M, Malmivaara A, Itälä A, Joukainen A, Nurmi H, Kalske J, Järvinen TL (December 26, 2013). "Arthroscopic Partial Meniscectomy versus Sham Surgery for a Degenerative Meniscal Tear". The New England Journal of Medicine. 369 (26): 2504–2514. doi: 10.1056/NEJMoa1305189 . PMID   24369076.
  8. ↑ Siemieniuk, Reed A. C.; Harris, Ian A.; Agoritsas, Thomas; Poolman, Rudolf W.; Brignardello-Petersen, Romina; Velde, Stijn Van de; Buchbinder, Rachelle; Englund, Martin; Lytvyn, Lyubov (2017-05-10). "Arthroscopic surgery for degenerative knee arthritis and meniscal tears: a clinical practice guideline". British Medical Journal. 357: j1982. doi:10.1136/bmj.j1982. ISSN   1756-1833. PMC   5426368 . PMID   28490431.
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