Menisceal Injuries

Question 1

What is function of the meniscus?

Answer 1

1. Optimise force transmission across the knee by
   
   • Increasing congruency
     
     • increased contact area -> decreased point loading
   • shock-absorption
     
     • the mensicus is ore ealstic than articualr cartilage so absorbs shock
   • Transmits 50% WB load in extension & 85% in flexion
2. ​Stability
   
   • ​meniscus deepens the tibial surface
   • acts as secondary stabiliser
     
     • medial meniscus- post horn of medial meniscus is main secondary stabiliser to anterior translation
     • lateral meniscus is less stabilising
       
       • has 2x the excursion cf medial m
   • ***the meniscus become primary stabilisers in ACL def knee***

Question 2

What are the meniscus made of?

Answer 2

• Fibroelastic cartilage
  
  • interlacing network of collagen, procollagen, glycoproteins and cellular elements
  • 66-75% water
  • 90% type 1 collagen
  • fibres- allow the mensicus to expand under compression and increase contact area of joint
    
    • ​radial
    • longitudinal ( circumferential)
      
      • ​help dissipate hoop stresses
      • vertical matress captures

Question 3

What is the shape of the medial and lateral meniscus?

Answer 3

Medial

• C shaped w triangular X section
• av width 9-10mm
• av thickness 3-5mm

Lateral

• More circular ( the horns are closer together & approximate at ACL)
• covers a larger portion of the articular surface
• av width 10-12mm
• ab thickness 4-5 mm

Question 4

What are the attachment of the meniscus?

Answer 4

• Transverse ligament
  
  • connects medial and lateral meniscus anteriorly
• Coronary ligament
  
  • connects mensicus peripherally
  • medial mensicus has less mobility w more rigid peripheral fixation cf lateral
• Meniscofemoral ligaments
  
  • conects meniscus into substance of PCL
  • orginate post horn of lateral meniscus
    
    • Ligament of Humphrey ( ant)
    • Ligament of Wrisberg (post)

Question 5

What is the blood supply of the medial and lateral meniscus?

Answer 5

Medial

• Medial inferior genicular artery
  
  • supplies peripheral 20-30% of medial m

Lateral

• Lateral inferior genicular artery
  
  • supplies periohery 10-25% lateral m
  • central 75% recieves nutrition thru diffusion

Question 6

What is the innervation of the meniscus?

Answer 6

• Peripheral 2/3rds innervated by type 1 & 11 nerve endings
• Post horn highest concentration of mechanioreceptors

Question 7

What is the potential of healing of menisceal tears?

Answer 7

• Tears in peripheral 25% red zone
  
  • can heal by fibrocartilage scar formation
  • **fibrochondrocyte **is cell responsible for healing
  • peripheral tears <4mm have best healing potential
• Tears in central 75%
  
  • have limited or no intrinsic healing potential due to poor blood supply

Question 8

Describe the movements of the meniscus in knee movements?

Answer 8

• Anterior movement with extension
• Posterior movement with flexion
• lateral meniscus has more mobility than medial due to less ligament attachments

Question 9

What increases the risk of menisceal tears?

Answer 9

• In an ACL deficient knee

Question 10

Describe the aetiology of medial mensiceal tears cf lateral ?

Answer 10

• Medial
  
  • More common than lateral
  • the exception is in Acute ACL tears when Lateral tears are more common
  • Degenerative tears in older pts occur in Posterior horn medial meniscus

Question 11

How are menisceal tearas classified?

Answer 11

• By location
  
  • Red zone ( outer 3rd, vascularised)
  • Red-White sone ( middle 3rd)
  • White zone ( inner 3rd, avascular
• Size
• Pattern
  
  • Vertical /longitudinal
    
    • common, esp ACL tears
    • repair the peripheral
  • Bucket handle
    
    • vertical tear which may displace into notch
  • Oblique/parrot beak
    
    • may cause mechanical locking
  • Radial
  • Horizontal
    
    • more common older pts
    • assoc w menisceal cysts
  • Complex

Question 12

What are the presentation of menisceal injury?

Answer 12

• Symptoms
  
  • pain localised medial/lateral
  • mechanical locking/clicking
  • delayed/intermittent swelling
• Signs
  
  • Joint line tenderness
  • effusion
  • mcmurray’s test

Question 13

What is seen on imaging of menisceal injury?

Answer 13

• Xray
  
  • normal in young pts
  • menisceal calcifications in crystalline arthropathy
• MRI
  
  • sensitive but high false positive rate
  • Double PCL = bucket handle menisceal tear
  • paramedial cyst= menisceal tear

Question 14

What is the tx of menisceal injury?

Answer 14

Non operative

• rest, NSAIDS, Rehab
  
  • 1st line of tx for degenerative tears

Operative

• Partial meniscectomy
  
  • tears not amenable to repair
  • >80% satisfaction at FU
  • 50% have fairbank radiographic changes ( osteophytes, falttening, Joint space narrowing)
  • predictors of sucess
    
    • <40 yrs
    • normal alignment
    • minimal/no arthritis
    • single tear
• Menisceal repair
  
  • ​for peripheral in red zone
  • rim width is the distance form tear to peripheral meniscocapsular junction
  • rim width correlates w ability of repair to heal( lower has better blood supply)
  • Vertical/longitudinal tear
  • 1-4cm length
  • combined with ACL reconstruction - greatest success
  • 70-95% success
• Menisceal transplantation
  
  • young pt w near total meniscectomy exp lateral

Question 15

What are the outcomes of menisceal transplantation?

Answer 15

• Requires 8-12 months for graft to fully heal
• return to sport 6- 9 months
• 10 yr fu
  
  • persistent improvement in subhective pain and functional scores
  • most had radiological progression of degenerative chnages
  • retears or extrusion common

Question 16

What are the oucomes of total meniscectomy?

Answer 16

• 20% had significant arthritic lesions and 70% have radiographic changes 3 years post surgery
• 100% arthritis at 20 years
• severity of degeneratiev changes is proportional to % of meniscus that was removed
• Now only historical interest only

Question 17

How would you repair a menisceal tear?

Answer 17

• Inside out technique
  
  • gold standard
  • medial approach to capsule
    
    • expose capsule by incising sartorius fascia, retracting pes tendons and semimembranosus posteriorly and develop plane between medial gastrocnemius and capsule
  • Lateral approach to capsule
    
    • expose capsule by developinf plane between iliotibial band and biceps tendon interval. retract lat head of gastrocnemius posteriorly
• All inside technique -suture device w plastic /bioabsorbale anchors
  
  • most common
  • many complications- device breakage/iatrogenic chondral injury
• Outside in
• open repair
  
  • uncommon except knee dislocations
• Technique
  
  • vertical mattress suture strongest co they capture cicrumferential fibres

Question 18

What are the risk of menisceal tear repair?

Answer 18

• Saphenous nerve and vein ( medial approach)- 7%
• Peroneal neuropathy
• popliteal vessels
• deep infection 1%
• Sterile effusion 2%
• Athrofibrosis 6%
• superifical infection 1%

Question 19

What is a meniscal cyst?

Answer 19

• a condition characterised by a local collection of synovial fluid within or adjacent to the meniscus
• most commonly assoc with menisceal tear
• location
  
  • perimeniscal cyst
    
    • medial more common> lat
  • Parameniscal cyst- Baker’s cyst
  • xtruded fluid outside meniscus
  • usually between semimembranosus & medial head of gasronemius

Question 20

Describe the presentation of meniscal cyst?

Answer 20

• Symptoms
  
  • asymptomatic
  • pain
  • locking/clicking
  • dealyed/intermittent knee swelling
• Exam
  
  • popliteal mass
  • crepitus
  • joint line tenderness

Question 21

What imaging is useful and what is seen with a meniscal cyst?

Answer 21

• MRI
  
  • most sensitive
  • cyst bright on T2
  • xrays normal in young pt with acute meniscal injury

Question 22

Describe the tx of meniscal cyst?

Answer 22

Non operative

• Rest, NSAIDS, Rehabilitation
  
  • 1st line
• Aspiration and steriod injection
  
  • isolated baker’s cyst in young pt
  • more outcome in older degenerative tears w cyst

Operative

• Arthroscopic debridment, cyst decompression & partial meniscal resection
  
  • incomplete meniscal resection-> recurrence
• Cyst excision using open posterior approach
  
  • ​paramenisceal cyst
  • prone
  • curved incision
  • interval between semimembraneous and gastronemius
  • sharp dissection of cyst margins to capsule

Question 23

What is a discoid meniscus?

Answer 23

• Abnormal development of the meniscus-> hypertrophic and discoid shaped meniscus
• Discoid meniscus is > than usual
• aka popping knee syndrome
• present 3-5% population
• location
  
  • usual Lateral Meniscus
  • 25% bilateral

Question 24

Name and decsribe the classification of Discoid meniscus?

Answer 24

• Watanabe Classification
• Type 1- Complete
• Type 2- Incomplete
• Type 3- Wrisberg ( lack of poor meniscotibial attachment to tibia)

Question 25

What is the presentation of a discoid meniscus?

Answer 25

• Symptoms
  
  • Clicking, pain and mechanical locking
  • often symptomatic in adolscent
• Exam
  
  • mechnical symptoms more pronunced in extension

Question 26

What is seen on imaging of a discoid meniscus?

Answer 26

• Xrays
  
  • widening of joint space due to widening of cartilage ( up to 11cm)
  • Squaring of lateral condyle w cupping of lateral tibial plateau
  • hypoplastic lateral intercondylar space
• MRI
  
  • study of choice
  • bow tie sign - 3 or more sagittal images w meniscal continuity
  • coronal image will show flat meniscus extending across entire lateral compartment

Question 27

What is the tx of discoid meniscus?

Answer 27

Non operative

• Observation
  
  • asymptomatic without tears

Operative

• Partial meniscectomy and saucerization
  
  • for pain and mechanical symptoms
  • menisceal tear/ menisceal detachment
  • obtain anatomical looking meniscus w debridment
  • repair meniscus if detached ( Wrisberg variant)