MENISCI

histology

Water( 75%)

Collagen type 1

Proteoglycans

elastin

Collagen fibers

Circumferential fibers(majority)

Radial fibers

Perforating fibers

Role of hoop tension in menisci. Hoop tensiondeveloped in menisci acts to keep them between bones

Radial tear eliminates hoop tension and damages meniscus function

Anatomy

• Attached to the capsule except where the popliteus tendon is interposed laterally

• Loosely attached to the tibial plateaus by the coronary ligaments

• Avascular except near their peripheral attachments

Vascular supply

• lateral and medial geniculate vessels

• depth of peripheral vascular penetration is 10% to 30% of the width of the medial meniscus and

• 10%to 25% of the width of the

lateral meniscus

FUNCTIONA. act as a joint

filler, compensating for gross incongruity between femoral and tibial articulating surfaces

B. prevent capsular and synovial impingement during flexion-extension

function• joint lubrication• helping to distribute synovial fluid• nutrition of the articular cartilage• Stability especially rotary stabilizer• smooth transition from a pure hinge

to a gliding or rotary motion as the knee moves from flexion to extension

Load bearing

• Cover 1/2-to 2/3 of the articular surface

• Carry40%-70% of weight force

• medial meniscus 50%

• Lateral meniscus 70%

Effects of meniscectomy

Medial meniscectomy

↓contact area by 70%

↑contact stress by 100%

Meniscal movement• The menisci follow the tibial condyles

during flexion and extension• during rotation they follow the femur

and move on the tibia• Medial meniscus:Ant /Post attachments

follow the tibia, but its intervening part follows the femur and becomes distorted

• Lateral meniscus:is firmly attached posteriorly and less likely to be injured

Meniscectomy and joint laxity

• Intact ligaments→little joint laxity

• Ligamentus insufficiency→↑joint laxity

• ACL insufficiency→forces in the medial meniscus increase significantly

• ACL insufficiency+medial meniscectomy:↑AP translation

• ACL insufficiency+lateral meniscectomy:↕AP translation

MECHANISM OF TEAR

• rotational force while the joint is partially flexed

• vigorous internal rotation of the femur on the tibia results in meniscal catching

• meniscus torn longitudinally when the joint is suddenly extended

meniscaltears

• Longitudinal: The most common type usually involve the posterior segment Most involve the inferior rather than . . the superior surface medial meniscus ≈ lateral meniscus• Horizontal/oblique/radial usually lateral meniscus Usually between middle and anterior third

Predisposing factors

• Degeneration• Cyst• Discoid meniscus• Ligament or muscle insufficiency• Knee instability• Abnormal mechanichal axes

DIAGNOSIS• History:• may not be obtained, especially when

tears of abnormal or degenerative menisci in a middle age person

• Locking or no locking: may not be recognized consider absence of normal recurvatum Usually only with longitudinal bucket handle tear• R/O pseudolocking

Giving way

• Is not especific• Results from: Muscle(quadriceps) insufficiency Patellar problems Instability Loose body

Giving way

Giving way due to

meniscal tear

•On rotary movements•With a feeling of subluxation or knee jumping

Giving way due to other

causes

•During flexion against resistance•Walking down stairs

Effusion

• Acute: usually denotes a hemarthrosis, and it can occur when the vascularized periphery of a meniscus is torn

• Late: Tears occurring within the body of a meniscus or in degenerative areas may not produce a hemarthrosis

signs• Quadriceps atrophy

• Joint line tenderness localized to posterolateral or posteromedial(the most important physical finding)

• Tears of one meniscus can produce pain in the opposite compartment of the knee. This is most commonly seen with posterior tears of the lateral meniscus

Mc murray test• Palpate posteromedial/ posterolateral• Rotate leg external or

internal• Move knee from full

flexion to extension• Before 90˚→posterior horn• After 90˚→mid/ant horn

Apley grind testCheck menisci during compression

squat testPain localized to joint line is more important than pain during ext/int rotation

Thessaly test• Knee in 5˚ and

20˚ flexion• Accuracy rate

95%• Always done on

the normal knee first to teach the pt

paraclinic

• X ray: routine AP/LAT/intercondylar/sky line views

• Arthrography• MRI: sensitivity →65% specificity→95%

accuracy→85%

NONOPERATIVE MANAGEMENT

cylinder cast or knee immobilizer worn for 4 to 6 weeks

Strengthen muscles around the knee as well as the hip

criteria

• ZONE• TEAR TYPE• CHRONICITY• SIZE(cm)

A suitable candidate

• NonChronic• Stable( incomplete or could not be displaced

more than 3 mm from the intact peripheral rim)

• Peripheral• <5mm• no other pathological condition

Reparability of Meniscal Tears

• ZONE• TEAR TYPE• CHRONICITY• SIZE(cm)

Ideal indication

• Acute• 1- to 2-cm• Longitudinal• Peripheral• young individual• in conjunction with anterior cruciate

ligament reconstruction

Open or arthroscopic repair

• Open:• posterior horn peripheral tears if posteromedial or

posterolateral capsular reconstructions are being done concurrently

• Arthroscopic: • lateral meniscus• necessary for tears at or near the junction of the vascular and

avascular zones• Medial menisci tears that extend deep to the collateral ligament

DO NOT FORGET• For younger,active patients,ligamentous

stabilizationshould accompany meniscal suture because of thedecreased likelihood of healing and increased risk of re-rupture in a knee with ligamentous laxity

MENISCECTOMY

• Increasing degenerative changes were noted, especially after total meniscectomy

• After subtotal excision degeneration is localized

• degenerative change directly proportional to the amount of meniscus removed

Complete or incomplete

• Complete removal of the meniscus is justified only when it is irreparably torn

• Total meniscectomy is no longer considered the treatment of choice in young athletes

• Subtotal excision is easier by arthroscopy

LATE CHANGES AFTER MENISCECTOMY

• meniscectomy often is followed by degenerative changes within the joint

• after partial medial meniscectomy 88% to 95% of patients reporting good to excellent results.

AUTOGRAFTS AND ALLOGRAFTS• Indications: skeletally mature too young for TKA significant pain and limited function conservative therapy failed mechanical tear no synovial disease younger than 40 years normal mechanical alignment stable knee Outerbridge grade I or grade II articular cartilage changes pain localized to the affected compartment

AUTOGRAFTS AND ALLOGRAFTS

• Contraindications knee instability

varus-valgus malalignment

advanced osteoarthritis is an absolute contraindication

questionsremain about their survivorship and function

THE END