Menisci, often referred to as articular discs, are specialized crescent-shaped structures made of fibrocartilage. These pads are situated within certain joints, acting as important components for joint health and function. While present in areas like the wrist and temporomandibular joint, their role is most prominent in the knee. They contribute to the overall mechanics of these joints, enabling smoother movement and helping to maintain joint surface integrity.
Anatomy and Structure
The knee joint contains two prominent menisci: the medial and lateral. The medial meniscus is C-shaped, located on the inner side of the knee, and is more firmly attached to the joint capsule and the medial collateral ligament, which limits its mobility. The lateral meniscus, found on the outer side of the knee, is O-shaped and more mobile due to fewer attachments.
Both menisci are composed of fibrocartilage, a tough and flexible tissue that provides structural integrity. They have a wedge-like cross-section, thicker at their periphery and thinning towards their inner free edge. This shape helps optimize load transmission across the joint.
The blood supply to the menisci is limited. Only the outer one-third receives a direct blood supply, while the inner two-thirds are largely avascular, relying on synovial fluid for nutrition. This restricted vascularity impacts their healing potential. Menisci also possess nerve endings, contributing to pain perception and proprioception.
Essential Roles of Menisci
Menisci perform several functions within the knee joint, contributing significantly to its health and smooth operation. A primary function is shock absorption, where they distribute forces across the joint, protecting the articular cartilage. This cushioning effect helps prevent damage to the joint surfaces during activities involving impact.
They also play a role in load distribution by increasing the contact area between the femur (thighbone) and tibia (shinbone). This expanded contact area reduces stress on the joint surfaces, which is particularly important during movements that place high loads on the knee. Without the menisci, contact pressure between the bones can significantly increase.
Menisci contribute to knee joint stability, especially during rotational and flexion movements. Their wedge shape helps deepen the tibial plateau, improving the fit between the femoral condyles and the tibial surface. Furthermore, they aid in joint lubrication and nutrition by spreading synovial fluid across the articular cartilage. This process helps reduce friction and nourishes the cartilage cells. The menisci also provide proprioception, informing the brain about joint position and movement.
Common Injuries
Meniscal injuries are common, with tears being a frequent issue. These tears can vary in pattern, depending on the mechanism of injury and the individual’s age.
Injuries typically arise from two main causes: acute trauma or degenerative processes. Acute tears often occur during sports activities involving sudden twisting, pivoting, or direct blows to the knee. These traumatic injuries are common in athletes.
Degenerative tears result from gradual wear and tear on the meniscus, becoming more common with aging. Risk factors for meniscal tears include age, participation in certain sports, obesity, and occupations requiring frequent kneeling or squatting.
Symptoms and Treatment Approaches
Meniscal injuries typically present with characteristic symptoms. Pain in the knee is common, often worsening with twisting or squatting movements. Swelling and stiffness may develop. Mechanical symptoms like clicking, popping, or a sensation of the knee catching or locking are also frequently reported. Individuals might also experience a feeling of the knee giving way or have difficulty fully straightening or bending the leg.
Diagnosis of a meniscal tear usually involves a physical examination of the knee, where a doctor checks for tenderness along the joint line. Specific tests, such as the McMurray test, can help identify a tear by eliciting pain or a clicking sensation with certain knee movements. Imaging tests, particularly magnetic resonance imaging (MRI), confirm the presence and characteristics of a meniscal tear. X-rays may also be used to rule out other bone-related issues.
Treatment approaches depend on the tear’s size, location, and the patient’s age and activity level. Conservative management is often the initial approach for smaller tears or degenerative issues. This typically involves rest, ice, compression, and elevation (RICE protocol) to manage pain and swelling. Physical therapy is also a component of conservative treatment, focusing on restoring range of motion, strengthening surrounding muscles, and improving knee function. Pain medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs), may also be recommended.
If conservative measures are not effective or for more severe tears, surgical intervention may be considered. Arthroscopy, a minimally invasive procedure, is commonly used to either repair the torn meniscus or trim away the damaged portion (meniscectomy). The decision to repair or remove depends on the tear’s location, as tears in the well-vascularized outer zone have a better healing potential. It is important to consult a medical professional for an accurate diagnosis and appropriate treatment plan.