Discoid Meniscus

Introduction
Abnormal development of the meniscus leads to a hypertrophic and discoid shaped meniscus discoid meniscus is larger than usual Present in 3-5% of population usually lateral meniscus involved 25% bilateral Also referred to as "popping knee syndrome"
Classification
Watanabe classification Type I - complete Type II - incomplete Type III - Wrisberg (lack of posterior meniscotibial attachment to tibia)
Presentation
History pain, clicking, mechanical locking often becomes symptomatic in adolescence Physical exam mechanical symptoms most pronounced in extension
Imaging
Radiographs widened joint space due to widened cartilage space (up to 11mm) squaring of lateral condyle with cupping of lateral tibial plateau hypoplastic lateral intercondylar spine MRI diagnosis can be made with 3 or more 5mm sagital images with meniscal continuity ("bow-tie sign") sagittal MRI will show abnormally thick and flat meniscus coronol MRI will show thick and flat meniscal tissue extending across entire lateral compartment
Treatment
Nonoperative observation indicated for asymptomatic discoid meniscus without tears Operative partial menisecetomy and saucerization indications pain and mechanical symptoms meniscal tear or meniscal detachment technique obtain anatomic looking meniscus with debridement repair meniscus if detached (Wrisberg variant)

TAG

(OBQ07.129) An 11-year-old soccer player presents with snapping and discomfort along the lateral joint line of the knee. Examination shows a 10 degree loss of active extension. An AP radiographs is shown in Figure A. Sequental sagittal MRI images of the lateral compartment of the knee are shown in Figure B. What is the most appropriate course of action? Topic

Review Topic

FIGURES: A

1. Physical therapy with a focus on concentric knee strengthening
2. Non-weightbearing for 6 weeks
3. Arthroscopic saucerization of the lateral meniscus and/or meniscal repair
4. Open lateral menisectomy
5. Arthroscopic microfracture treatment of the defect on the lateral femoral condyle

PREFERRED RESPONSE ▶

DISCUSSION: The history, radiographs, and MRI are consistent with a diagnosis of discoid lateral meniscus. Surgery for discoid menisci is indicated for persistent pain or motion loss in order to prevent further meniscal damage. The classification system most widely used for discoid meniscus is that of Watanabe et al (Illustration A), who described three types of discoid lateral menisci based on arthroscopic appearance. In this classification, discoid menisci with normal peripheral attachments are either type I (complete) or type II (incomplete). Type III discoid menisci, the so-called Wrisberg ligament type, are described as lacking posterior capsular attachments with the exception of the posterior meniscofemoral ligament, thus producing the classic “snapping knee” syndrome. Complete meniscectomy of discoid lateral meniscus is avoided due to the development of early degenerative changes. Most authors now recommend repair of a detached posterior or peripheral attachment, with saucerization of the discoid morphology depending on the underlying meniscal shape and presence of a meniscal tear. Klingele et al found that 28.1% of patients in their series of discoid menisci had peripheral rim instability, and instability was more common in patients with a complete discoid morphology and in younger patients.

Illustrations: A

REFERENCES:

1. Klingele KE, Kocher MS, Hresko MT, Gerbino P, Micheli LJ. Discoid lateral meniscus: prevelance of peripheral rim instability. J Pediatric Orthop 2004; 24 79-82 PMID:14676539 (Link to Abstract)

2. 45.Watanabe M. Arthroscopy of the knee joint. In: Helfet AJ, ed. Disorders of the Knee. Philadelphia, Pa.: Lippincott; 1974:45.

Question Authors:

Patrick McCulloch MD, Derek Moore, Eric Shirley MD,

Please Rate Educational Value!

4.0

Average 4.0 of 8 Ratings

TAG

(OBQ05.166) An 8-year-old boy was playing at school and took a direct blow to his knee causing pain and swelling. His pediatrician ordered an MRI which is shown in Figure A. The patient was referred to your office for a consultation. He denies any past history of pain, clicking, or locking. His knee exam is unremarkable. Radiographs of the knee in your office are normal. What course of action will you recommend? Topic

Review Topic

FIGURES: A

1. Surgical debridement and repair
2. Ligamentous reconstruction
3. Casting in 45 degrees of flexion
4. Knee immobilizer and non weight bearing for 6 weeks
5. Observation

PREFERRED RESPONSE ▶

DISCUSSION: The clinical presentation and MRI are consistent with an asymptomatic lateral discoid meniscus without evidence of tear. No intervention is indicated for asymptomatic discoid menisci. When these are symptomatic, surgical saucerization and possible repair are indicated. Klingele et al reviewed a series of 112 surgically treated patients and found that 28% were unstable, and 69% had an associated meniscus tear. Ogut et al reported their follow-up on 11 surgically treated discoid mensici, and had 82% excellent results and 18% good results. Davidson et al reported their results in 32 children who underwent partial, complete or no excision of the discoid meniscus, with 16 excellent, 10 good, 6 fair and 4 poor results.

REFERENCES:

1. Klingele KE, Kocher MS, Hresko MT, Gerbino P, Micheli LJ. Discoid lateral meniscus: prevalence of peripheral rim instability. J Pediatr Orthop. 2004 Jan-Feb;24(1):79-82. PMID:14676539 (Link to Abstract)

2. Davidson D, Letts M, Glasgow R. Discoid meniscus in children: treatment and outcome. Can J Surg. 2003 Oct;46(5):350-8. PMID:14577707 (Link to Abstract)

3. Ogüt T, Kesmezacar H, Akgün I, Cansü E. Arthroscopic meniscectomy for discoid lateral meniscus in children and adolescents: 4.5 year follow-up. J Pediatr Orthop B. 2003 Nov;12(6):390-7. PMID:14530697 (Link to Abstract)

Question Authors:

Aaron Bott MD, Patrick McCulloch MD,

Please Rate Educational Value!

3.0

Average 3.0 of 8 Ratings

Textbooks

Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
Orthopaedic Knowledge Update 10, John M Flyn. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2011
Hoppenfeld SP. Surgical Exposures in Orthopaedics: The Anatomic Approach. Lipponcott, Williams, and Wilkins, Philadelphia, PA, Copyright 2009
Orthopaedic In-training Examination (OITE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Self-Assessment Examination (SAE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012

Undefined

Klingele KE, Kocher MS, Hresko MT, Gerbino P, Micheli LJ. Discoid lateral meniscus: prevelance of peripheral rim instability. J Pediatric Orthop 2004; 24 79-82 PMID:14676539 (Link to Abstract)
45.Watanabe M. Arthroscopy of the knee joint. In: Helfet AJ, ed. Disorders of the Knee. Philadelphia, Pa.: Lippincott; 1974:45.
Klingele KE, Kocher MS, Hresko MT, Gerbino P, Micheli LJ. Discoid lateral meniscus: prevalence of peripheral rim instability. J Pediatr Orthop. 2004 Jan-Feb;24(1):79-82. PMID:14676539 (Link to Abstract)
Davidson D, Letts M, Glasgow R. Discoid meniscus in children: treatment and outcome. Can J Surg. 2003 Oct;46(5):350-8. PMID:14577707 (Link to Abstract)
Ogüt T, Kesmezacar H, Akgün I, Cansü E. Arthroscopic meniscectomy for discoid lateral meniscus in children and adolescents: 4.5 year follow-up. J Pediatr Orthop B. 2003 Nov;12(6):390-7. PMID:14530697 (Link to Abstract)

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