Medial meniscus
Head of right tibia seen from above, showing menisci and attachments of ligaments. (Medial meniscus visible at left.)
Left knee-joint from behind, showing interior ligaments.
Latin	meniscus medialis
Gray's	subject #93 343

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.^[1] It is also referred to as the internal semilunar fibrocartilage. It is a common site of injury, especially if the knee is twisted, as commonly occurs in contact sports.

Contents 1 Structure 2 Function 3 Injury 4 See also 5 Additional images 6 Notes 7 References 8 External links

[edit] Structure

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.^[1]

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.^[2]

[edit] Function

The medial meniscus separates the tibia and femur and serves as a shock absorber, to increase the contact area between the bones, reducing the peak contact force experienced. It also reduces friction between the two bones to allow smooth movement in the knee.

[edit] Injury

Acute injury to the medial meniscus fairly often accompanies an injury to the ACL (anterior cruciate ligament) 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.^[3][4][5]

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.

[edit] See also

• meniscus
• Tear of meniscus
• cartilage
• unhappy triad
• meniscal cartilage replacement therapy

[edit] Additional images

Right knee-joint, from the front, showing interior ligaments.

Sagittal section of right knee-joint.

Capsule of right knee-joint (distended). Posterior aspect.

Normal medial meniscus

[edit] Notes

[edit] References

• Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol. 1: Locomotor System (5th ed.). Thieme. ISBN 3-13-533305-1. 
• Thieme Atlas of Anatomy: General Anatomy and Musculoskeletal System. Thieme. 2006. ISBN 1-58890-419-9. 

[edit] External links

• SUNY Figs 17:07-06
• Medial+meniscus at eMedicine Dictionary
• lljoints at The Anatomy Lesson by Wesley Norman (Georgetown University) (antkneejointopenflexed)
• The KNEEguru

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.

v • d • e Joints and ligaments of lower limbs (TA A03.6, GA 3.333) Coxal/hip femoral (iliofemoral, pubofemoral, ischiofemoral) · head of femur · transverse acetabular  · acetabular labrum · capsule · zona orbicularis Knee-joint Capsule · Anterior meniscofemoral ligament · Posterior meniscofemoral ligament extracapsular: patellar · popliteal (oblique, arcuate) · collateral (medial/tibial, fibular/lateral) intracapsular: cruciate (anterior, posterior) · menisci (medial, lateral) · transverse Infrapatellar fat pad Tibiofibular Superior tibiofibular anterior of the head of the fibula · posterior of the head of the fibula Inferior tibiofibular anterior of the lateral malleolus · posterior of the lateral malleolus other Interosseous membrane of leg Joints of foot Talocrural/ankle medial: medial of talocrural joint/deltoid (anterior tibiotalar, posterior tibiotalar, tibiocalcaneal, tibionavicular) lateral: lateral collateral of ankle joint (anterior talofibular, posterior talofibular, calcaneofibular) Subtalar/talocalcaneal anterior/posterior · lateral/medial · interosseous Transverse tarsal Talocalcaneonavicular dorsal talonavicular · plantar calcaneonavicular/spring · bifurcated (calcaneonavicular) Calcaneocuboid dorsal calcaneocuboid · long plantar · plantar calcaneocuboid · bifurcated (calcaneocuboid) Distal intertarsal Cuneonavicular plantar · dorsal Cuboideonavicular plantar · dorsal Intercuneiform plantar · dorsal · interosseous Other Tarsometatarsal/Lisfranc plantar · dorsal Intermetatarsal/metatarsal plantar · dorsal · interosseous · superficial transverse · deep transverse Metatarsophalangeal plantar · collateral Interphalangeal plantar · collateral Arches Longitudinal · Transverse

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