Description

• The menisci are fibrocartilaginous structures between the femoral condyles and the tibial plateaus.
• The menisci help to stabilize the knee (with the anterior cruciate ligament [ACL]) and distribute forces across the joint to provide shock absorption.
• Meniscal tears can lead to knee pain and disability and, ultimately, are a risk factor for the development of knee osteoarthritis (OA).

Pediatric Considerations

• Meniscal injuries are less common in children aged <10 years. In this population, they are often due to a discoid meniscus.
• MRI is still the study of choice but is less sensitive and specific for diagnosing meniscal tears in children aged <12 years.
• Increased BMI in pediatric patients correlates with more complex tears and lower repair success rates.

Epidemiology

Bimodal age distribution—young athletes (traumatic) and older patients (degenerative)

Incidence
Medial meniscus more commonly injured

Prevalence

• One of the most common musculoskeletal injuries
• Meniscal surgery is the most common type of orthopedic surgery performed in the United States.

Etiology and Pathophysiology

• Traumatic tears are acute. They generally occur due to a twisting motion of the knee with foot planted.
  • Common in younger patients (aged <40 years) without underlying knee OA
  • Manifests with sudden pain
• Degenerative tears are chronic. They generally occur with overuse and minimal trauma.
  • There is an age related increase in prevalence, and they are often comorbid with knee OA.
  • Symptoms evolve slowly.

Genetics
No specific gene locus has been identified.

Risk Factors

• Nonmodifiable risk factors: male, discoid meniscus, ligamentous laxity
• Traumatic tear:
  • High degree of physical activity (especially cutting sports)
  • ACL insufficiency
• Degenerative tear:
  • Increased age (>60 years)
  • Obesity
  • Work-related kneeling/squatting/climbing stairs

General Prevention

• Treatment and rehabilitation of previous knee injuries, particularly ACL injuries
• Strengthening and increased flexibility of quadriceps and hamstring muscles
• Weight management

Commonly Associated Conditions

• Traumatic tear: ACL concomitantly torn in 1/3 of cases
• Degenerative tear: OA, Baker cyst (greater association with medial meniscal tears)