Background: In previous studies, 5% to 20% of patients with a discoid lateral meniscus eventually require surgery bilaterally for symptomatic discoid menisci. However, there are little published data specifically on children who require treatment for discoid menisci in both knees. The purpose of this study is to identify differences in clinical and arthroscopic findings between children who require bilateral versus unilateral treatment for symptomatic discoid lateral menisci.
Methods: We retrospectively reviewed the records of all patients aged 18 years or younger requiring treatment of discoid lateral meniscus between 1998 and 2007. Data were collected on 16 patients (32 knees) with symptomatic bilateral discoid menisci and 60 patients treated unilaterally with an asymptomatic contralateral knee.
Results: At initial presentation, children who were treated bilaterally for discoid menisci were younger than those treated unilaterally (10.4 vs. 12.5 y; P=0.021). Patients under 12 years of age were 4.6 times more likely to eventually require surgery on both knees (P=0.015). Watanabe classification was as follows: complete, 65% bilateral versus 30% unilateral; incomplete, 22% bilateral versus 68% unilateral; and Wrisberg, 13% bilateral versus 2% unilateral (P<0.001). The odds of current or future bilateral symptoms requiring treatment were 4.5 times higher in patients with a complete discoid meniscus (P=0.0017) and 8.4 times higher in those with a Wrisberg type (P=0.048). A tear of the lateral meniscus was more likely to be found intraoperatively in unilateral knees than bilateral (90% vs. 72%; P=0.037).
Conclusions: Patient education and long-term follow-up are important for children who present with a discoid meniscus at a young age or with a complete or Wrisberg type, as these patients may be at increased odds of symptomatic discoid meniscus in the contralateral knee, even several years later. Furthermore, evaluation and treatment of discoid lateral meniscus requires vigilance for meniscal tears.
Level of evidence: Prognostic study, level III.