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- 2 menisci: Medial and lateral C-shaped fibrocartilagenous structures located intra-articularly between the femoral condyles and the tibal plateaus
- Each meniscus has a body, anterior horn, and posterior horn.
- The menisci play a role in load distribution, absorbing forces, and stabilizing the knee. Also contribute to joint lubrication and nutrition
- After the age of 10, the menisci begin to devascularize:
- In adults, the outer 1/3 remains vascularized, whereas the inner 2/3 is avascular and heals poorly
- The medial meniscus is attached to the joint capsule and medial collateral ligament. It is less mobile, and concurrent medial collateral ligament (MCL)/anterior cruciate ligament (ACL) injuries are more common
Meniscal tears in older patients are more likely due to chronic degeneration of the meniscus that can result in a tear with minimal trauma.
- It is rare to sustain a meniscal injury <10 years old or prior to physial fusion.
- Meniscal tears in young children are often due to a discoid meniscus:
- MRI is less sensitive and specific in diagnosing meniscal tears in children <12 (2)[B]:
- On MRI, normal vascular meniscal tissue can be misinterpreted as a tear
- Meniscal tears are more common in the 3rd–5th decades of life.
- More common in males: Male > Female (2.5:1–4:1)
- Injuries are more common in the medial meniscus because of its reduced mobility and role as the primary weight-bearing surface.
- Injuries can be acute or degenerative:
- Degenerative tears more likely >40
- Acute traumatic tears more likely in adolescents and adults <40; 80–90% occur during athletics
- Increased age
- High degree of physical activity (especially pivot/cutting sports)
- Tibiofemoral arthritis
- ACL insufficiency
- Posterior cruciate ligament (PCL) insufficiency
A congenital abnormality leading to discoid meniscus increases the risk of meniscal tear among children. No specific gene locus has been identified.
- Strengthening of quadriceps and hamstring muscles
- Conditioning while participating in sports
- Treatment and rehabilitation of previous knee injuries, particularly ACL injuries
- Improving core proprioception and hamstring flexibility may prevent knee injuries in female athletes.
- Acute tears typically occur due to a twisting motion of the knee while the foot is planted. Also can occur due to a hyperflexion event:
- Common mechanisms during sports: Cutting, decelerating, hyperflexing, or landing from a jump
- Degenerative tears occur secondary to minimal trauma
Commonly Associated Conditions
- ACL is concomitantly torn in 1/3 of cases.
- MCL and lateral collateral (LCL) ligament tears
- Tibial plateau fractures
- Femoral shaft fractures
- Tibiofemoral joint dislocation (seen occasionally)