- a thickened and wafer shaped lateral meniscus varient;
- discoid meniscus may range from complete disc to a ring shaped meniscus;
- occurs in upto 5% of population (but only a % of these are symptomatic) (prevalence may be higher in orientals (15%));
- usually involves lateral meniscus and is frequently bilateral (20% of pts);
- although a congenital etiology for discoid menisci has been proposed, the discoid variant is not normally found in the fetus;
- clinically patients may complain of pain, swelling, and snapping;
- the classic discoid snapping knee is usually caused by a discoid meniscus w/ a deficient menisco-tibial ligament;
- based on the degree of peripheral attachments to the tibia plateau;
- complete vs. incomplete
- the terms complete and incomplete are sometimes used to describe the shape of the discoid meniscus (incomplete having
a more semilunar shape);
- the same terms (complete and incomplete have also been used to describe whether the meniscus is stable vs unstable;
- complete type has normal peripheral attachments & normal mobility.
- these meniscal varients tend to be stable due to the presence of a posterior menisco-femoral ligament;
- when symptomatic, either a tear or a posterior menisco-femoral detachment is usualy present;
- treatment: arthroscopic partial menisectomy and meniscoplasty
- unstable (wrisberg)
- these are unstable and hypermobile to due lack of posterior tibio-meniscal ligaments;
- has only one attachment posperiorly, posterior meniscofemoral ligament,
- on knee extension, abnormal meniscus is pulled posteromedially into the intercondylar notch (instead of gliding forward)
due to the action of the meniscofemoral ligaments;
- probably responsible for the true "snapping knee;"
- total menisectomy is recommended for Wrisberg type deformity since lacks posterior meniscal tibial attachments & has
unstable posterior horn;
- ref: Does discoid lateral meniscus have inborn peripheral rim instability? Comparison between intact discoid lateral
meniscus and normal lateral meniscus
- anterior or posterior megahorn;
- lateral joint space widening and cupping of lateral tibial plateau;
- hypoplasia of the lateral tibial spine;
- suggestive finding include meniscal tissue on 3 or more contiguous saggital cuts;
- note: a classic false negative can occur w/ an unstable (Wrisberg) type of discoid meniscus which maintains a relative
- Non Operative Treatment:
- an asymptomapic discoid meniscus does not require treatment and prognosis is generally good;
- symptoms of popping by itself is not harmful unless it is accompanied by pain or swelling of the knee;
- knee arthroscopy for medial sided pain, current recommendation is to leave the asymptomatic discoid meniscus alone;
- ref: Cautious surgery for discoid menisci.
- Operative Treatment:
- all forms of operative treatment are controversial;
- pain, swelling, & a history of trauma are relative indications for arthroscopy;
- tears of a stable meniscus may require resection of the discoid lateral meniscus, leaving peripheral rim intact (meniscoplasty);
- rescetion is often difficult because of increased meniscal thickness
- w/ a unstable discoid meniscus, a complete menisectomy is required
Long-Term Results of Arthroscopic Reshaping for Symptomatic Discoid Lateral Meniscus in Children
Congenital discoid lateral meniscus in children. A follow-up study and evolution of management.
The discoid lateral-meniscus syndrome.
Discoid lateral meniscus in children. Long-term follow-up after excision.
Lateral Meniscal Variants: Evaluation and Treatment.
Management of discoid lateral meniscus tears: observations in 34 knees
Discoid lateral meniscus: prevalence of peripheral rim instability.
Torn discoid lateral meniscus treated using partial central meniscectomy and suture of the peripheral tear
Symptomatic Bilateral Discoid Menisci in Children: A Comparison With Unilaterally Symptomatic Patients
Clinical Outcomes as a Function of Meniscal Stability in the Discoid Meniscus: A Preliminary Report