Medial meniscus

Original Editor - ­Aarti Sareen

Top Contributors - Aarti Sareen, Rachael Lowe, Evan Thomas, Oyemi Sillo and Fasuba Ayobami

Introduction

The word menisci are derived from the Greek work meniskos, which means "crescent". At knee joint the menisci plays a major role in congurency of the joint. Menisci forms the concavity in which the femoral condyles sits. Menisci rests between the thigh bone femur and the tibia and there are two knee joint ligaments. They are a type of cartilage in the joint. The rubbery texture of the menisci is due to their fibrocartilagenous structure. Their shape is maintained by the collagens within them. One meniscus is on the inner side of your knee--the medial meniscus. The other meniscus is on the outer side of your knee--the lateral meniscus.

Anatomy and attachment

The medial meniscus is approximately 1.4 in (3.5cm) in length. The anterior horn of the medial meniscus is attached to the anterior surface of the tibia well off the tibial plateau. The anterior fibers of the anterior cruciate attachment merge with the transverse ligament, which connects the anterior horns of the medial. The posterior horn of the medial meniscus is firmly attached to the posterior aspect of the periphery to the joint capsule. At its midpoint, the meniscus is firmly attached to the femur and tibia through a condensation in the joint capsule known as the deep medial ligament. The medial meniscus has no direct attachment to any muscle, but indirect capsule connections to the semimembranosus may provide some retraction of the posterior horn.
Medial menisci are C shaped wedge fibrocartilagenous structure located between condyle of femur and tibia. It is somewhat more in C shape as compared to lateral menisci as it is medial meniscus are clear of the plateau anteriorly and posteriorly. Anteriorly, it is also attached to lateral menisci by transverse ligament and patella either directly or by patellomeniscal ligaments which are anterior capsular thickenings[1]. Its anterior portion is much narrower than the posterior portion and the narrower portion is less prone to injury also.

Meniscus sup view Gray349.png

VASCULAR SUPPLY:

The vascular supply of the menisci originates predominately from the inferior and superior lateral and medial genicular arteries. During the first year of life the meniscus contains blood vessels throughout its body but when the weight bearing starts the vascularity and the circulatory network diminish and only 25-33% area remain vascular by the capillaries of the capsule and synovial membrane[2]. The vascularity diminishes so much that in 4th decade of life only the periphery is vascular whereas the center of the menisci is avascular. The center portion is completely dependent upon the synovial fluid diffusion for nutrition[3]. The central avascular portion of menisci either does not heal completely or heal at all after injury[2].

NERVE SUPPLY:

The horns of the menisci and the peripheral vascularized portion of the meniscal bodies are well innervated with free nerve endings (nociceptors) and three different mechanoreceptors (Ruffini corpuscles, pacinian corpuscles, and Golgi tendon organs)[2][4][5].

Injury/Tear

The most common mechanism of menisci injury is a twisting injury with the foot anchor on the ground, often by another player's body. A slow twisting force may also cause the tear.Damage to the meniscus is due to rotational forces directed to a flexed knee (as may occur with twisting sports) is the usual underlying mechanism of injury [6][7]. The meniscal tear is of following types:

  • Longitudinal
  • Radial
  • Bucket handle
  • Flap
  • Horizontal cleavage
  • Degenerative
Types of meniscal tears.jpg

Meniscus injuries commonly occur in contact sports; often in combination with ligament injuries, particularly when the medial meniscus is involved. This is partly because the medial meniscus is attached to the medial collateral ligament, and partly because tackles are often directed towards the lateral side of the knee, causing external rotation of the tibia. Injury to the medial meniscus is about 5 times more common than injury to the lateral meniscus. In cases of external rotation of the foot and lower leg in relation to the femur, the medial meniscus is most vulnerable. A varus force applied to the flexed knee when the foot is planted and the femur rotated internally can result in a tear of the medial meniscus.
The patient comes up with major complain of knee pain, swelling and knee locking which is when the patient is unable to straighten the leg fully. This can be accompanied by a clicking feeling.
The diagnosis of an medial meniscus injury is considered to be fairly certain if three or more of the following findings are present:[6]

  • Tenderness at one point over the medial joint line
  • Pain in the area of the medial joint line during hyperextension of the knee joint
  • Pain in the area of the medial joint line during hyperflexion of the knee joint
  • Pain during external rotation of the foot and the lower leg when the knee is flexed at different angles around 70–90°
  • Weakened or hypotrophied quadriceps muscle.

Diagnosis

Diagnosis can be made on the basis of

  • Special test
  • X-ray
  • MRI

Special Tests:

Although there are several tests for a meniscus tear, none can be considered definitive without considerable experience on the part of the examiner. Patient history and the mechanism of injury also provide a major source of information. The most commonly used special tests are...

X-Ray:

X-ray is done in weight-bearing but is not helpful in detecting the medial meniscal tear, but, can detect other associated conditions at bony level.

Magnetic Resonance Imaging:

Meniscal tear can be well appreciated on an MRI.

Resources

Clinical Practice Guideline: Meniscal and Articular Cartilage Lesions

References

  1. Tuxoe JI, Teir M, Winge S, et al.: The medial patellofemoral ligament: A dissection study. Knee Surg Sports Traumatol Arthrosc 10:138–140, 2002.
  2. 2.0 2.1 2.2 Gray JC: Neural and vascular anatomy of the menisci of the human knee. J Orthop Sports Phys Ther 29:23–30, 1999.
  3. McCarty EC, Marx RG, DeHaven KE: Meniscus repair: Considerations in treatment and update of clinical results. Clin Orthop 402:122–134, 2002.
  4. Zimny ML, Albright DJ, Dabezies E: Mechanoreceptors in the human medial meniscus. Acta Anat (Basel) 133:35–40, 1988.
  5. Mine T, Kimura M, Sakka A, et al.: Innervation of nociceptors in the menisci of the knee joint: An immunohistochemical study. Arch Orthop Trauma Surg 120:201–204, 2000.
  6. 6.0 6.1 Peterson,Renström. SPORTS INJURIES:Their Prevention and Treatment.Third Edition.
  7. Brunker,Khan.Clinical Sports Medicine.3rd Edition.