Meniscus Flashcards
Consequences of meniscal deficiency
Increased risk of OA
higher incidence with
Lateral > medial
Total mensicectomy > partial mensicectomy
Function
- Improve congruency - - > distribute load evebly across the knee throughout ROM
- stabiliser of the knee
- Contribute to proprioception, cartilage nutrition and lubrication
Histology
75% water
20% type I collagen
5% other substances (proteoglycans, elastin, type II collagen, fibrochondrocytes)
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
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
ESSKA/ISAKOS Classification based on
- Tear depth (full /partial thickness)
- Residual rim width (<3mm, 3-5mm, >5mm)
- Location (posterior, mid-body, anterior)
‘Hidden lesions’
= Menisco-capsular ‘ramp’ lesions
= peripheral vertical longitudinal tears at the Menisco-capsular junction of the posterior horn of the medial meniscus
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
Vertical radial lesions
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
Meniscus repair is particularly important in ACL-injured knees, reducing residual laxity
Lateral meniscal tears occur in around 20% of ACL injuries
Meniscal repair is superior to resection in terms of
Function, return to sport and cartilage protection
Rough guide for repairable tears
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
Inside-out technique
Remains gold standard
Particularly useful for long (>3cm) or bucket handle tears
All-inside technique
Fas-TFix
Particularly useful for posterior third tears, can also be used in middle third tears
Outside-in technique
Useful for anterior third tears that are difficult to reach
Risk for secondary mensicectomy where higher?
Medial –> indications for surgical repair are more strict for medial tears
How much % repaired meniscus fail?
Approximately 15%, require secondary mensicectomy
Indication for meniscal reconstruction by allograft transportation
If repair is not possible and if the patient develops post-meniscectomy symptoms of pain on activity
Predominantly circumferential arrangement of the collagen fibres
Vital to meniscal function
Convert comprehensive forces into a radially directed force, which is distributed and resisted as ‘hoop stresses’ within the meniscus
Why are the menisci especially important in ACL-deficient knee?
Contribute to stability
With the posterior horn of the medial meniscus functioning as a secondary stabiliser against anterior tibial drawer
Defunctioning meniscus can lead to
Rapid degeneration of the joint
Development of spontaneous osteonecrosis of the knee (SPONK)
Presentation
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
Sign of a potential posterior horn tear
Posterior pain with forced deep flexion
Do Mc Murray and Thessaly test, but extremely variable in sensitivity
Structures at risk during meniscus repair
Posterior horn repair - popliteal artery
Lateral repair - common peroneal nerve
Medial repair - saphenous nerve
Mc Murray test
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
Appley’s grind test
Patient lies prone with the knee flexed to 90°
Internal and external rotation of the tibia is combined with downward pressure
Discoid meniscus
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
Findings of discoid meniscus on knee radiographs
Squaring of lateral condyle
Widening of joint space
Cupping of the lateral tibial plateau
Hypoplastic lateral intercondylar spine
When do meniscal tears primarily occur?
In conjunction with horizontal cleavage tears of the lateral meniscus
Popliteal (Baker) cyst
Usually resolve with treatment of the primary meniscal disorder
Usually located between the semimembranosus and the medial head of the gastrocnemius
Diagnostic feature of discoid meniscus in MRI
Appearance of a contiguous lateral meniscus on three consecutive sagittal images on MRI
