Double-Layered Lateral Meniscus Including a Ring-Shaped Accessory Meniscus: A Case Report

Area of Science:

• Orthopedic Surgery
• Pediatric Orthopedics
• Sports Medicine

Background:

• Meniscal tears are common knee injuries, but anatomical variations can complicate diagnosis and treatment.
• A double-layered lateral meniscus is an exceptionally rare congenital anomaly.

Observation:

• An 11-year-old male presented with left knee pain, initially diagnosed via MRI as a horizontal meniscal tear.
• Arthroscopy revealed a double-layered lateral meniscus, with a mobile, ring-shaped accessory meniscus fused to a normal meniscus at the posterior horn.

Findings:

• The accessory meniscus was identified as the source of pain due to its increased mobility.
• Arthroscopic resection of the superior accessory meniscus led to substantial symptom improvement.

Implications:

• This case highlights the importance of considering rare anatomical variations in pediatric knee pain.
• Arthroscopic resection of accessory menisci is a viable treatment for symptomatic double-layered lateral menisci.
• Successful surgical correction allows for a full return to athletic activities without long-term degenerative changes.