Menisci

Each of our knee joints contains two menisci. These are two large, wedge-shaped pieces of fibrocartilage. They differ slightly in shape, lie completely within the joint, and are enclosed by the joint capsule. The outer (lateral) meniscus has a more circular O-shape, while the inner meniscus has a more crescent-like C-shape. Both menisci are divided into a posterior and an anterior horn.

 Role and Function

The role of the menisci is to bridge the significant difference in shape between the femur and tibia of the knee joint and to reduce joint incongruity. This increases the stability of the knee joint while simultaneously reducing the load on the hyaline joint cartilage surfaces of these bones.

Henry Vandyke Carter creator QS:P170,Q955620 derivative work: Hellerhoff Henry Graycreator QS:P170,Q40319 , Gray348-2, marked as public domain, details on Wikimedia Commons

Structure

The menisci are also a connective tissue structure composed of cells and matrix. Physiologically, they are comparable to articular cartilage (see also our blog post on Articular Cartilage). Menisci consist of approximately 75% water.

Both menisci are thickest in the outer region and become thinner towards their center. The outer, thicker region also contains the most cells and is the most highly innervated and vascularized area.

Braus, Hermann, Braus 1921 284, marked as public domain, details on Wikimedia Commons

The alignment and orientation of the fibers vary significantly across the different regions depending on the load and demands placed on them.

Since the menisci only have blood vessels and nerves in their outer, thicker regions, a high-quality synovial fluid is vital for their nourishment (synovial fluid is produced by the joint capsule). To promote and support diffusion and osmotic processes, they require a regular alternation of loading and unloading to maintain their structure and function.

Henry Vandyke Carter Henry Gray, Gray348-de, marked as public domain, details on Wikimedia Commons

The outer edges of the menisci are fused with the joint capsule, though the inner medial meniscus is attached significantly more securely (due to its additional connection with the medial collateral ligament of the knee, which is more strongly fused with the joint capsule and the medial meniscus on the inside than on the outside). Consequently, the outer lateral meniscus possesses greater mobility than the inner medial meniscus—and this reduced mobility of the medial meniscus makes it correspondingly more susceptible to traumatic injuries.

Degeneration and Trauma

The most common causes of problems are age-related or immobilization-induced degenerative changes, as well as traumatic injuries.

If the joint is not kept in motion, degenerative changes set in very rapidly.

Immobilization quickly leads to a heavy loss of water and ground substance, which leaves the collagen network no longer under tension (just like with articular cartilage) and severely reduces the load-bearing capacity of the cartilage and menisci.

Because this makes the menisci more easily deformable, the stress on the fiber network increases. At the same time, the mobility of the menisci relative to the articular cartilage surface is reduced.

Fundamentally, any knee joint movements involving a high range of motion and/or speed can cause injury to the menisci. Most often, trauma is caused by combined movements (flexion, buckling, and external rotation). Since the inner medial meniscus has less mobility, as explained above, it is more vulnerable to injury and therefore more frequently affected by traumatic damage. It is not uncommon for the aforementioned combined movement to also compromise the medial collateral ligament (MCL) and the anterior cruciate ligament (ACL) (the so-called unhappy triad). 

Training

Just like with articular cartilage, targeted training improves the micellar alignment of the menisci and thereby enhances their tensile strength. Furthermore, reversible hypertrophy (generating more cartilage cells) reduces incongruity by expanding the contact surfaces. This improves pressure elasticity and shock absorption in the knee joint.

Training and exercise do not just improve the adaptive capacity of cartilage tissue: strengthening the skeletal muscles and improving coordination helps unload the knee joint during movement sequences, especially under higher stress, protecting both the tissue and your body.

Therapy

To ensure optimal healing and regeneration of injured tissue, regular physiological loading is required. This is the only way the body can rebuild a functional, resilient, and strong new tissue. Without the appropriate physiological stimuli, the body will produce an inferior replacement or scar tissue of lower quality.

For knee injuries, patients should therefore keep moving and loading the knee in a modified, reduced form whenever possible.

At BodyLab, our physiotherapy and osteopathy specialists thoroughly understand anatomical and physiological relationships. We know exactly which therapeutic options and training methods are best for injuries, discomfort, or specific issues, and we are happy to guide and instruct you.

If active loading is not yet possible (after surgery or injury) or no longer possible, we can use passive joint techniques—sometimes utilizing compression or traction—to improve the quality and function of the menisci and the entire joint as a functional unit, effectively reducing pain and discomfort.

Once again, the golden rule applies: Life is movement!

Whenever you need us, we are here for you!

Your BodyLab Team, your specialists for movement and body aches

Osteopathy and Physiotherapy | Rehabilitation and Training

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You can find more information on cartilage tissue in our blog on our homepage under Articular Cartilage.

Learn more about our Intervertebral Disc - Structure & Function in another blog post.

Cover Image Credit

Henry Vandyke Carter Henry Gray, Gray349, marked as public domain, details on Wikimedia Commons