Meniscus

Question 1

Consequences of meniscal deficiency

Answer 1

Increased risk of OA

higher incidence with
Lateral > medial
Total mensicectomy > partial mensicectomy

Question 2

Function

Answer 2

1. Improve congruency - - > distribute load evebly across the knee throughout ROM
2. stabiliser of the knee
3. Contribute to proprioception, cartilage nutrition and lubrication

Question 3

Histology

Answer 3

75% water

20% type I collagen

5% other substances (proteoglycans, elastin, type II collagen, fibrochondrocytes)

Question 4

chances of healing in a meniscus repair highest in the well-vascularised peripheral third of the meniscus in adults and potentially the outer two-thirds of the meniscus in younger children

Answer 4

At birth vascular margin is higher (up to 50% of the width) but this slowly declines to the adult stage 10-25/30%) by the age of 12

Question 5

ESSKA/ISAKOS Classification based on

Answer 5

1. Tear depth (full /partial thickness)
2. Residual rim width (<3mm, 3-5mm, >5mm)
3. Location (posterior, mid-body, anterior)

Question 6

‘Hidden lesions’

= Menisco-capsular ‘ramp’ lesions
= peripheral vertical longitudinal tears at the Menisco-capsular junction of the posterior horn of the medial meniscus

Answer 6

Associated with increased mobility of the posterior horn

Tend to occur in association with ACL injuries

May not be identifiable on MRI or even at arthroscopy without specifically probing the ramp area from a posteromedial portal and viewing from the notch area

Question 7

Vertical radial lesions

Answer 7

Lesions of up to 60% of the inner zone can generally be trimmed

Lesions reaching the peripheral zone, disrupt the resistance to hoop stresses with functional consequences similar to total mensicectomy and should be repaired as repair can return peak pressures to normal

Question 8

Meniscus repair is particularly important in ACL-injured knees, reducing residual laxity

Answer 8

Lateral meniscal tears occur in around 20% of ACL injuries

Question 9

Meniscal repair is superior to resection in terms of

Answer 9

Function, return to sport and cartilage protection

Question 10

Rough guide for repairable tears

Answer 10

Tears less than 4mm from the meniscal rim

Ideally within 4 weeks of injury

In patients who will comply with the necessary rehab, avoiding sport for 4 months minimum

Question 11

Inside-out technique

Answer 11

Remains gold standard

Particularly useful for long (>3cm) or bucket handle tears

Question 12

All-inside technique

Fas-TFix

Answer 12

Particularly useful for posterior third tears, can also be used in middle third tears

Question 13

Outside-in technique

Answer 13

Useful for anterior third tears that are difficult to reach

Question 14

Risk for secondary mensicectomy where higher?

Answer 14

Medial –> indications for surgical repair are more strict for medial tears

Question 15

How much % repaired meniscus fail?

Answer 15

Approximately 15%, require secondary mensicectomy

Question 16

Indication for meniscal reconstruction by allograft transportation

Answer 16

If repair is not possible and if the patient develops post-meniscectomy symptoms of pain on activity

Question 17

Predominantly circumferential arrangement of the collagen fibres

Answer 17

Vital to meniscal function

Convert comprehensive forces into a radially directed force, which is distributed and resisted as ‘hoop stresses’ within the meniscus

Question 18

Why are the menisci especially important in ACL-deficient knee?

Answer 18

Contribute to stability

With the posterior horn of the medial meniscus functioning as a secondary stabiliser against anterior tibial drawer

Question 19

Defunctioning meniscus can lead to

Answer 19

Rapid degeneration of the joint

Development of spontaneous osteonecrosis of the knee (SPONK)

Question 20

Presentation

Answer 20

Painful knee, often following acute injury

Might have effusion (swelling often develops over the course of 24hrs after injury, rather than the more rapidly appearing and larger swelling seen with haemarthrosis after injuries such as ACL tears)

Locking, catching or painful giving way

Question 21

Sign of a potential posterior horn tear

Answer 21

Posterior pain with forced deep flexion

Do Mc Murray and Thessaly test, but extremely variable in sensitivity

Question 22

Structures at risk during meniscus repair

Answer 22

Posterior horn repair - popliteal artery

Lateral repair - common peroneal nerve

Medial repair - saphenous nerve

Question 23

Mc Murray test

Answer 23

Provocative test

Tibia is internally and externally rotated whilst the knee is flexed and extended

A varus or valgus force is also applied depending on which meniscus is being tested

Question 24

Appley’s grind test

Answer 24

Patient lies prone with the knee flexed to 90°

Internal and external rotation of the tibia is combined with downward pressure

Question 25

Discoid meniscus

Answer 25

Watanabe classification

Type I
complete, normal peripheral attachment

Type II
incomplete, normal peripheral attachment

Type III
Wrisberg, lacking posterior capsular attachment with the exception of the posterior meniscofemoral ligament
Produce the classic snapping knee syndrome
Surgery : repair of a detached posterior periperal attachment, with saucerization of the discoid morphology depending on the underlying morphology, indicated for persistent pain or motion loss in order to prevent further meniscal damage

Question 26

Findings of discoid meniscus on knee radiographs

Answer 26

Squaring of lateral condyle
Widening of joint space
Cupping of the lateral tibial plateau
Hypoplastic lateral intercondylar spine

Question 27

When do meniscal tears primarily occur?

Answer 27

In conjunction with horizontal cleavage tears of the lateral meniscus

Question 28

Popliteal (Baker) cyst

Answer 28

Usually resolve with treatment of the primary meniscal disorder

Usually located between the semimembranosus and the medial head of the gastrocnemius

Question 29

Diagnostic feature of discoid meniscus in MRI

Answer 29

Appearance of a contiguous lateral meniscus on three consecutive sagittal images on MRI