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Discoid Meniscus Workup

  • Author: Ralph DiLibero, MD; Chief Editor: Thomas M DeBerardino, MD  more...
 
Updated: Jul 27, 2015
 

Imaging Studies

Radiography

The widened and thickened discoid meniscus may be demonstrated on routine radiography of the knee. Radiography may reveal any combination of widening of the lateral joint clear space and cupping (see the images below). Cupping is a reversal of the normally flat to convex bony shape of the lateral tibial plateau into a more concave shape.

Radiograph of an 8-year-old child with bilateral d Radiograph of an 8-year-old child with bilateral discoid menisci, diagnosis confirmed by MRI. Patient is only symptomatic on the left side. Patient underwent arthroscopy and partial meniscectomy and is now asymptomatic. Image courtesy of Dennis P. Grogan, MD.
Knee radiograph of a 17-year-old athlete with a di Knee radiograph of a 17-year-old athlete with a discoid lateral meniscus. The lateral joint space is widened, and the tibial plateau has a flattened appearance. Image courtesy of Robert D. Bronstein, MD.

Magnetic resonance imaging

The positive predictive value (PPV) of magnetic resonance imaging (MRI) for demonstrating a discoid meniscus tear is approximately 57%, whereas the PPV for predicting a discoid meniscus is approximately 92%.[7] The PPV is determined by creating a fraction in which the sum of the number of true- and false-positive results is the denominator and the number of true-positive results is the numerator, then multiplying that fraction by 100%. (See the images below.)

MRI scan of typical discoid meniscus. Image courte MRI scan of typical discoid meniscus. Image courtesy of William Morrison, MD.
MRI scan of typical discoid meniscus. Image courte MRI scan of typical discoid meniscus. Image courtesy of William Morrison, MD.
Coronal MRI scan demonstrating a complete discoid Coronal MRI scan demonstrating a complete discoid meniscus (arrow). Image courtesy of Robert D. Bronstein, MD.

MRI is the modality of choice to evaluate a discoid meniscus before surgery.[13, 14]  The most common diagnostic finding is that of a "bow-tie" sign, a viewing of the anterior and the posterior meniscal sections connected together on more than two sagittal MRI serial images.

A discoid lateral meniscus commonly occurs bilaterally, and, in patients who are symptomatic, an intrameniscal signal is also commonly found.

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McMurray Test

When the McMurray test is performed on a patient with a discoid meniscus, a loud click or snap is both felt and heard. For more information on the McMurray test, please see Tests to evaluate the menisci, under the heading Clinical Details  in Knee, Meniscal Tears (MRI).

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Contributor Information and Disclosures
Author

Ralph DiLibero, MD Branch Chief, Benefits Division, California Department of Health Services

Ralph DiLibero, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, California Orthopedic Association, Los Angeles County Medical Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Thomas M DeBerardino, MD Associate Professor, Department of Orthopedic Surgery, Consulting Surgeon, Sports Medicine, Arthroscopy and Reconstruction of the Knee, Hip and Shoulder, Team Physician, Orthopedic Consultant to UConn Department of Athletics, University of Connecticut Health Center

Thomas M DeBerardino, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Orthopaedic Association, American Orthopaedic Society for Sports Medicine

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Arthrex, Inc.; Ivy Sports Medicine; MTF; Aesculap; The Foundry, Cotera; ABMT<br/>Received research grant from: Histogenics; Cotera; Arthrex.

Additional Contributors

Phillip J Marone, MD, MSPH Clinical Professor, Department of Orthopedic Surgery and Department of Rehabilitation Medicine, Jefferson Medical College of Thomas Jefferson University

Phillip J Marone, MD, MSPH is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American College of Surgeons, American Medical Association, American Orthopaedic Society for Sports Medicine, Philadelphia County Medical Society

Disclosure: Nothing to disclose.

References
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  10. Yoo WJ, Choi IH, Chung CY, Lee MC, Cho TJ, Park MS, et al. Discoid lateral meniscus in children: limited knee extension and meniscal instability in the posterior segment. J Pediatr Orthop. 2008 Jul-Aug. 28(5):544-8. [Medline].

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  15. Andrisani, Miller, Rubenstein. Surgical Management of Discoid Meniscus. Techniques in Knee Surgery. 2006. 128-33.

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  17. Smith CF, Van Dyk GE, Jurgutis J, Vangsness CT Jr. Cautious surgery for discoid menisci. Am J Knee Surg. 1999 Winter. 12(1):25-8. [Medline].

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  20. Ahn JH, Lee SH, Yoo JC, Lee YS, Ha HC. Arthroscopic partial meniscectomy with repair of the peripheral tear for symptomatic discoid lateral meniscus in children: results of minimum 2 years of follow-up. Arthroscopy. 2008 Aug. 24(8):888-98. [Medline].

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Radiograph of an 8-year-old child with bilateral discoid menisci, diagnosis confirmed by MRI. Patient is only symptomatic on the left side. Patient underwent arthroscopy and partial meniscectomy and is now asymptomatic. Image courtesy of Dennis P. Grogan, MD.
MRI scan of typical discoid meniscus. Image courtesy of William Morrison, MD.
MRI scan of typical discoid meniscus. Image courtesy of William Morrison, MD.
Coronal MRI scan demonstrating a complete discoid meniscus (arrow). Image courtesy of Robert D. Bronstein, MD.
Knee radiograph of a 17-year-old athlete with a discoid lateral meniscus. The lateral joint space is widened, and the tibial plateau has a flattened appearance. Image courtesy of Robert D. Bronstein, MD.
Arthroscopic appearance of a complete discoid lateral meniscus. The probe is showing the medial extent of the lateral meniscus, which completely covers the lateral tibial plateau. Image courtesy of Robert D. Bronstein, MD.
Arthroscopic photograph following saucerization of a discoid lateral meniscus. The edge of a horizontal tear that traversed the meniscus can be observed. Image courtesy of Robert D. Bronstein, MD.
 
 
 
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