Discoid Meniscus


Article Author:
Zackary Birchard


Article Editor:
Joshua Tuck


Editors In Chief:
Sisira Reddy
Joseph Nahas
Chokkalingam Siva


Managing Editors:
Avais Raja
Orawan Chaigasame
Khalid Alsayouri
Kyle Blair
Radia Jamil
Erin Hughes
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Navid Mahabadi
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beenish Sohail
Hajira Basit
Phillip Hynes
Sandeep Sekhon


Updated:
2/28/2019 8:29:12 AM

Introduction

Within the knee are two crescent-shaped menisci that act as shock absorbers between the femur and tibia, dispersing axial compressive loads. The menisci are fibrocartilaginous structures mainly composed of type I collagen. They have several functions including force transmission, increased joint congruency, and secondary stabilizers of the knee. The medial meniscus is typically more C-shaped and intimately in contact with the surrounding capsule. The lateral meniscus is more circular in shape and has increased mobility due to fewer capsular attachments.

A discoid meniscus is an anatomical variant from the normal crescent-shaped meniscus, in which the discoid meniscus is often thicker and takes on a disc or saucer shape. These variants are more commonly disposed to injury in comparison to a normally shaped meniscus. When these variants are present and symptomatic, they can often lead to a popping sensation within the knee which commonly is referred to as “popping knee syndrome.”[1][2][3][4]

Etiology

A discoid meniscus is due to a congenital, anatomical occurrence. The cause of discoid meniscus is not presently known. Injuries to the meniscus are common and may arise following a twisting or pivoting motion through the joint; although, the lack of an inciting event is also common. The presence of a discoid meniscus is associated with an increased risk of meniscal tears.

Epidemiology

Some studies have shown that approximately 3% to 5% of the population have a discoid meniscus. Within this population, the lateral meniscus is by far the more common anatomic variant, with only a few case reports of medial discoid meniscus reported. Up to 25% of cases of the discoid meniscus is bilateral at presentation. The discoid meniscus can be divided into one of the three following subtypes based on the orientation or pattern of the meniscus. The three types are incomplete, complete, and Wrisberg variant. Incomplete, (type 1), is simply defined by a slightly thicker and wider than normal meniscus.  A complete, (type 2), discoid meniscus covers the entire portion of the superior aspect of the tibia within the affected compartment. The Wrisberg variant, (type 3), is a hypermobile discoid meniscus that lacks posterior meniscotibial attachments. Type 3 is, therefore, the most unstable of the three types of the discoid meniscus.

Overall, the incidence of discoid meniscus is much higher in Asian countries compared to Western nations. In Japan and Korea rates as high as 10-13% have been reported, almost double what is reported in the US.

Pathophysiology

The abnormal shape of the discoid meniscus predisposes the structure to injury. Partial or full tears can occur with or without a traumatic event, often leading to mechanical symptoms. A study conducted by Ouyang et al. 2015 showed that discoid meniscus tears are most often horizontal, while the majority of normal meniscus tears occur in a longitudinal or radial pattern.

Studies show that there is significant disorganization of the circular collagen bundle. In addition, the circumferentially arranged collagen fibers show a heterogeneous course. It is believed that there is a structural problem, with an abnormal vascularity and increased discoid thickness which makes it prone to tearing.

History and Physical

A patient that presents with symptomatic discoid meniscus will commonly have complaints of anterior and/or lateral knee pain with or without a popping sensation within the knee. This popping sensation is not always present but is often more common with activity. Other mechanical symptoms may also be reported by the patient, such as catching, locking or feelings of instability through the knee.  In the setting of a displaced meniscal tear, the patient may present lacking the ability to extend the knee fully. Trauma is not necessary to cause symptomatic discoid meniscus. If a discoid meniscus is symptomatic, the patient will often present during adolescence. A comprehensive knee examination should be completed, including visual inspection, a range of motion, neurovascular evaluation, ligamentous stability testing, and meniscus-specific special testing. Special tests specific to meniscal pathology should include medial or lateral joint line tenderness to palpation, McMurray’s test, Apley’s compression test, and Thessaly’s test.

Evaluation

Evaluation of a discoid meniscus is prompted by pain or mechanical symptoms described by the patient, although this can also be an incidental finding on MRI or x-ray. If a symptomatic discoid meniscus is suspected, the patient should be referred to an orthopedic surgeon for an evaluation. X-rays should be done first. Common findings on an x-ray of a discoid meniscus include a widened joint space and squaring of the lateral femoral condyle. Findings on an MRI of discoid meniscus include the “bow-tie sign” with three or more 5 mm sagittal images showing meniscal continuity, an abnormally thick or flattened meniscus on the sagittal cut, and thick/flat meniscal tissue that extends over the entirety of the involved compartment on coronal views.[5][6][7][8][9]

Treatment / Management

If a discoid meniscus is diagnosed incidentally in the absence of symptoms, no formal treatment is indicated. However, if a discoid meniscus is causing mechanical or painful symptoms, surgery is warranted. Most commonly, symptomatic discoid menisci are treated with arthroscopic saucerization, which is a procedure that utilizes shavers and biters to reshape the meniscus. The surgeon converts the discoid into a more anatomic crescent, meniscal shape. Certain tear patterns may be amenable to hybrid procedures, utilizing both saucerization and subsequent remaining meniscal repair. Hypermobile Wrisberg variants may warrant saucerization combined with meniscal fixation to the adjacent capsule to preserve native meniscal tissue. Post-operatively, weight-bearing is at the discretion of the surgeon.  Often, physical therapy is prescribed for muscle strengthening, increasing range of motion, edema control, balance, and coordination.

Staging

The Discoid Meniscus per Watanabe classification:

The complete type is the disc-shaped meniscus has a normal posterior attachment and totally covers the lateral tibial plateau. 

The incomplete type appears semilunar in shape and has a normal posterior attachment. However, it covers less than 80% of the lateral tibial plateau.

The Wrisberg type has a normal shape compared to the incomplete or complete type of discoid meniscus. However, the normal posterior meniscal attachment (coronary ligament) is missing. This type only has the Wrisberg ligament connecting to the posterior horn of the lateral meniscus.

Prognosis

Most reports indicate a good outcome after partial meniscectomy with or without repair of the meniscus. Follow up studies have not shown degenerative changes in 5 year follow up studies.

The prognosis is better in young patients.

Pearls and Other Issues

In the setting of total meniscectomy, meniscus allograft transplantation (MAT) may be a viable option. Yoon et al. 2014, followed a patient population that underwent this procedure with a mean follow-up period of 32 months to assess clinical outcomes following MAT. He found that at a minimum of 2 years, similar outcomes in knee function and pain were achieved among patients undergoing MAT for discoid meniscal tears versus non-discoid meniscal tears.

Enhancing Healthcare Team Outcomes

The diagnosis and management of discoid mensicus is with an interprofessional team that includes a primary care provider, nurse practitioner, sports physician, orthopedic surgeon, radiologist and a physical therapist. If a discoid meniscus is diagnosed incidentally in the absence of symptoms, no formal treatment is indicated. However, if a discoid meniscus is causing mechanical or painful symptoms, surgery is warranted.  The outcomes after surgery in young patients are good to excellent. However, physical therapy is required post surgery to regain muscle strength and range of motion. [10](Level V)

 


Interested in Participating?

We are looking for contributors to author, edit, and peer review our vast library of review articles and multiple choice questions. In as little as 2-3 hours you can make a significant contribution to your specialty. In return for a small amount of your time, you will receive free access to all content and you will be published as an author or editor in eBooks, apps, online CME/CE activities, and an online Learning Management System for students, teachers, and program directors that allows access to review materials in over 500 specialties.

Improve Content - Become an Author or Editor

This is an academic project designed to provide inexpensive peer-reviewed Apps, eBooks, and very soon an online CME/CE system to help students identify weaknesses and improve knowledge. We would like you to consider being an author or editor. Please click here to learn more. Thank you for you for your interest, the StatPearls Publishing Editorial Team.

Discoid Meniscus - Questions

Take a quiz of the questions on this article.

Take Quiz
What is the physical examination finding most commonly found on exam for a discoid meniscus and which compartment is discoid meniscus most frequently found?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which of the following makes the diagnosis of discoid meniscus?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
A skeletally immature patient presents to the office with anterior knee pain and describes a popping sensation. X-rays are ordered and show squaring of the lateral femoral condyle along with joint space widening, and cupping of the lateral tibial plateau. What is the diagnosis?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which of the following is not a test for the physical diagnosis of discoid meniscus?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
MRI of a 12-year-old female showed a Wrisberg type III lateral meniscus. What is the most appropriate initial treatment?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up

Discoid Meniscus - References

References

Farrell C,Kiel J, Anatomy, Bony Pelvis and Lower Limb, Medial Meniscus 2018 Jan;     [PubMed]
Lee SH, Editorial Commentary: Why Should the Contralateral Side Be Examined in Patients With Symptomatic Discoid Lateral Meniscus? Arthroscopy : the journal of arthroscopic     [PubMed]
Aydın Kabakçı AD,Büyükmumcu M,Akın D,Bilge O, Morphological structure and variations of fetal lateral meniscus: the significance in convenient diagnosis and treatment. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA. 2019 Jan 17;     [PubMed]
Jeon SW,Choi CH,Jung M,Chun YM,Kim SJ,Jin S,Kim SH, The Fate of the Contralateral Knee in Patients With a Lateral Discoid Meniscus. Arthroscopy : the journal of arthroscopic     [PubMed]
Masquijo JJ,Bernocco F,Porta J, Discoid meniscus in children and adolescents: Correlation between morphology and meniscal tears. Revista espanola de cirugia ortopedica y traumatologia. 2019 Jan - Feb;     [PubMed]
Tsujii A,Matsuo T,Kinugasa K,Yonetani Y,Hamada M, Arthroscopic minimum saucerization and inferior-leaf meniscectomy for a horizontal tear of a complete discoid lateral meniscus: Report of two cases. International journal of surgery case reports. 2018;     [PubMed]
Wilson PL,Wyatt CW,Romero J,Sabatino MJ,Ellis HB, Incidence, Presentation, and Treatment of Pediatric and Adolescent Meniscal Root Injuries. Orthopaedic journal of sports medicine. 2018 Nov;     [PubMed]
Sabbag OD,Hevesi M,Sanders TL,Camp CL,Dahm DL,Levy BA,Stuart MJ,Krych AJ, Incidence and Treatment Trends of Symptomatic Discoid Lateral Menisci: An 18-Year Population-Based Study. Orthopaedic journal of sports medicine. 2018 Sep;     [PubMed]
Bedoya MA,Barrera CA,Chauvin NA,Delgado J,Jaramillo D,Ho-Fung VM, Normal meniscal dimensions at different patient ages-MRI evaluation. Skeletal radiology. 2019 Apr;     [PubMed]
Ohnishi Y,Nakashima H,Suzuki H,Nakamura E,Sakai A,Uchida S, Arthroscopic treatment for symptomatic lateral discoid meniscus: The effects of different ages, groups and procedures on surgical outcomes. The Knee. 2018 Dec;     [PubMed]

Disclaimer

The intent of StatPearls is to provide practice questions and explanations to assist you in identifying and resolving knowledge deficits. These questions and explanations are not intended to be a source of the knowledge base of all of medicine, nor is it intended to be a board or certification review of Rheumatology. The authors or editors do not warrant the information is complete or accurate. The reader is encouraged to verify each answer and explanation in several references. All drug indications and dosages should be verified before administration.

StatPearls offers the most comprehensive database of free multiple-choice questions with explanations and short review chapters ever developed. This system helps physicians, medical students, dentists, nurses, pharmacists, and allied health professionals identify education deficits and learn new concepts. StatPearls is not a board or certification review system for Rheumatology, it is a learning system that you can use to help improve your knowledge base of medicine for life-long learning. StatPearls will help you identify your weaknesses so that when you are ready to study for a board or certification exam in Rheumatology, you will already be prepared.

Our content is updated continuously through a multi-step peer review process that will help you be prepared and review for a thorough knowledge of Rheumatology. When it is time for the Rheumatology board and certification exam, you will already be ready. Besides online study quizzes, we also publish our peer-reviewed content in eBooks and mobile Apps. We also offer inexpensive CME/CE, so our content can be used to attain education credits while you study Rheumatology.