Meniscus Cartilage: Functions, Anatomy, and Clinical Significance

What is the function of the meniscus cartilage?

The meniscus cartilage, located within the knee joint, primarily functions to distribute loads, absorb shock, and enhance the stability and lubrication of the knee, acting as a crucial intermediary between the femur and tibia.

Anatomy of the Meniscus

The knee joint, one of the most complex in the human body, relies heavily on the integrity of its soft tissues for optimal function. Among these critical structures are the menisci (plural for meniscus), two C-shaped, semi-circular wedges of fibrocartilage positioned between the femoral condyles (thigh bone) and the tibial plateau (shin bone).

• Medial Meniscus: The larger, more C-shaped meniscus located on the inner side of the knee. It is more firmly attached to the joint capsule and the medial collateral ligament (MCL), making it less mobile and thus more susceptible to injury.
• Lateral Meniscus: The smaller, more O-shaped meniscus on the outer side of the knee. It is less firmly attached and more mobile, allowing it to adapt better to knee movements and potentially reducing its risk of injury compared to the medial meniscus.

Composed primarily of water and a dense network of collagen fibers, the menisci are tough, elastic, and designed to withstand significant compressive and shear forces.

Primary Functions of the Meniscus

The menisci perform several vital roles that are indispensable for healthy knee mechanics and longevity.

• Load Distribution and Shock Absorption: This is arguably the most critical function. The menisci increase the contact area between the rounded femoral condyles and the relatively flat tibial plateau by approximately 70-75%. Without the menisci, the load would be concentrated on a much smaller surface area, leading to significantly higher stress on the articular cartilage of the tibia. By distributing forces over a larger area, they reduce peak stresses and act as crucial shock absorbers, dampening the impact of activities like walking, running, and jumping.
• Joint Stability: The menisci deepen the shallow tibial plateau, creating a more congruent joint surface for the femoral condyles. This "cupping" effect enhances the stability of the knee, particularly during flexion and extension, and helps prevent excessive anterior-posterior (front-back) and rotational movements of the femur on the tibia. They act as secondary stabilizers, especially when the primary ligaments are injured.
• Lubrication and Nutrition: Through their movement and compression, the menisci help to spread synovial fluid across the articular cartilage surfaces. Synovial fluid is essential for lubricating the joint, reducing friction, and providing nutrients to the avascular articular cartilage, contributing to the overall health and longevity of the joint.
• Proprioception: The menisci contain mechanoreceptors (nerve endings) that provide sensory feedback to the brain regarding the position and movement of the knee joint. This proprioceptive input is vital for coordinating muscle activity, maintaining balance, and ensuring proper joint mechanics during various activities.

Clinical Significance and Injury

Given their multifaceted roles, the integrity of the menisci is paramount for knee health. Meniscus tears are common injuries, often resulting from twisting motions, deep squats, or direct trauma. The specific function compromised depends on the type and location of the tear. A torn meniscus can lead to pain, swelling, clicking, locking, and a feeling of instability in the knee. Without the menisci's protective functions, the articular cartilage is subjected to increased stress, significantly accelerating the progression of osteoarthritis.

Preserving Meniscus Health

Maintaining the health of your menisci is crucial for long-term knee function. Strategies include:

• Proper Movement Mechanics: Focus on correct form during exercises and daily activities to avoid excessive twisting or compressive forces on the knee.
• Strength Training: Develop strong muscles around the knee (quadriceps, hamstrings, glutes) to provide dynamic stability and support for the joint.
• Flexibility and Mobility: Maintain good range of motion in the knee and surrounding joints to prevent undue stress during movement.
• Progressive Overload: Gradually increase training intensity and volume to allow the joint structures to adapt.
• Listen to Your Body: Address knee pain promptly and seek professional guidance if symptoms persist.

Conclusion

The meniscus cartilage is far more than just a simple cushion in the knee. It is an intricate, biomechanically sophisticated structure that plays a critical role in load management, joint stability, lubrication, and proprioception. Understanding its vital functions underscores the importance of protecting these structures to ensure optimal knee health and prevent degenerative changes throughout life.