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Orthopaedic

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Arthritis

Question
79 out of 101
 

True about knee joint as all except (DNB Dec 2011)



A Medial meniscus is more mobile that lateral

B Menisci made up of type I collagen

C Lateral covers more area than medial meniscus

D Medial more commonly injured

Ans. A

Medial meniscus is more mobile that lateral

Ref: Campbells 11th edition

Menisci

Differences and mechanism of injury

a. The peripheral edges of the menisci are convex, fixed, and attached to the inner surface of the knee joint capsule, except where the popliteus is interposed laterally; these peripheral edges also are attached loosely to the borders of the tibial plateaus by the coronary ligaments.

b. The inner edges are concave, thin, and unattached. The menisci are largely avascular except near their peripheral attachment to the coronary ligaments.

c. The inferior surface of each meniscus is flat, whereas the superior surface is concave, corresponding to the contour of the underlying tibial plateau and superimposed femoral condyle.

d. The medial meniscus is a C-shaped structure larger in radius than the lateral meniscus, with the posterior horn being wider than the anterior.

e. The anterior horn is attached firmly to the tibia and to the anterior cruciate ligament. Most of the weight is borne on the posterior portion of the meniscus..

f. Its entire peripheral border is firmly attached to the medial capsule and through the coronary ligament to the upper border of the tibia.

g. The lateral meniscus is more circular in form, covering up to two thirds of the articular surface of the underlying tibial plateau.

h. The posterior horn often receives anchorage also to the femur by the ligament of Wrisberg and the ligament of Humphry and from fascia covering the popliteus muscle and the arcuate complex at the posterolateral corner of the knee. The inner border, like that of the medial meniscus, is thin, concave, and free.

i. The tendon of the popliteus muscle separates the posterolateral periphery of the lateral meniscus from the joint capsule and the fibular collateral ligament.

j. The lateral meniscus is smaller in diameter, thicker in periphery, wider in body, and more mobile than the medial meniscus. It is attached to both cruciate ligaments and posteriorly to the medial femoral condyle by either the ligament of Humphry or the ligament of Wrisberg, depending on which is present; it is also attached posteriorly to the popliteus muscle.

k. In contrast, the medial meniscus is much larger in diameter, is thinner in its periphery and narrower in body, and does not attach to either cruciate ligament. It is loosely attached to the medial capsular ligaments.

l. The menisci follow the tibial condyles during flexion and extension, but during rotation, they follow the femur and move on the tibia; consequently, the medial meniscus becomes distorted.

m. Its anterior and posterior attachments follow the tibia, but its intervening part follows the femur; thus it is likely to be injured during rotation.

n. However, the lateral meniscus, because it is firmly attached to the popliteus muscle and to the ligament of Wrisberg or of Humphry, follows the lateral femoral condyle during rotation and therefore is less likely to be injured.

o. Vascular supply to the medial and lateral menisci originates predominantly from the lateral and medial geniculate vessels (both inferior and superior).

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