Cartilage and Meniscus Tears

by Robert Tallitsch, PhD | August 26, 2024

Video explaining the cartilage of the knee joint with a patient example that showcases meniscus tear repair!

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Overview

When someone says they injured their knee, one of two injuries typically come to mind: a torn meniscus or a torn ACL (anterior cruciate ligament). In this Brain Builder we will talk about the anatomical characteristics of the knee joint, what a meniscus is, why it is needed, and how one typically tears a meniscus. We will then discuss the signs and symptoms of a torn meniscus, and how a torn meniscus is treated.

Anatomy of the Knee Joint

The knee joint is a biaxial synovial joint. (See “Synovial Joints and Dislocations” for a discussion of the characteristics of a synovial joint.) The femoral condyles, tibial plateaus, and patella participate in the formation of the knee joint.

Like all synovial joints, the knee joint possesses a capsule, a synovial space filled with synovial fluid, and articulating hyaline cartilages. In addition, the knee has several accessory structures, including the cruciate ligaments, capsular ligaments, and the medial and lateral menisci. We will talk about the anatomy of the femoral condyles, tibial plateaus, patella, and medial and lateral menisci in more detail below.

Bones and Menisci of the Knee Joint

Distal Extremity of the Femur:

The distal extremity of the femur is made up almost exclusively by the medial and lateral condyles of the femur. Anteriorly the femoral condyles are united, forming the patellar surface. As you progress posteriorly and inferiorly the condyles separate, forming the intercondylar fossa. The condyles are completely covered with hyaline cartilage.

Patella:

The patella is a large sesamoid bone enclosed within the patella tendon. The posterior, articular surface of the patella is smooth and is completely covered with hyaline cartilage.

Proximal Articulating Surface of the Tibia:

The proximal surface of the tibia is composed of expanded tibial condyles. Posteriorly these condyles form the tibial plateau, which is the superior articulating surface of the tibia. The medial articulating surface is slightly concave, while the lateral articulating surface is slightly convex. These surfaces articulate with the femoral condyles of the knee joint.

Menisci of the Knee Joint:

The medial and lateral menisci of the knee joint are composed of fibrous cartilage (also termed fibrocartilage). The menisci serve to deepen the articulating surfaces of the tibial plateau, as well as cushions within the knee joint. As with all forms of mature cartilage, the menisci are avascular (lacking in blood vessels).

The medial meniscus is more C-shaped and, because of its extensive connective tissue attachments to the tibia and the tibial collateral ligament, it is less mobile than the circularly shaped lateral meniscus.

Movements of the Knee Joint and the Menisci of the Knee

The knee joint is capable of flexion, extension, and limited rotation. (For an explanation of joint movements see "Anatomical Movements"). As the knee extends to its maximum range when the foot is fixed in position (such as when it is planted on the ground) the medial condyle of the femur rotates medially on the tibial plateau. This movement passively “locks” the knee into position. Flexion of the knee, with the foot fixed in position, starts with a lateral rotation of the medial condyle of the femur on the tibial plateau, passively “unlocking” the knee.

The locking of the knee allows the lower limb to be a stable plateau with minimal continuous muscular action.

Meniscus Tears

Causes of Meniscus Tears

A meniscus tear may occur because of degenerative changes in the fibrous cartilage related to aging, or because of a traumatic injury. Meniscus tears are one of, if not the most common forms of sports injury.

Although a meniscus tear may occur because of contact during an athletic contest, a large number of meniscus tears occur not because of physical contact but because of the athlete pivoting or cutting as they run — such as a wide receiver cutting to the sideline to catch a pass or a basketball player cutting during a fast break to make a basket. As stated above, when the foot is planted, the medial condyle of the femur rotates medially on the tibial plateau, locking the knee. If the knee rotates too far during a pivoting or cutting movement there is a chance that a meniscus of the knee may tear.

Signs and Symptoms of a Torn Meniscus

Most individuals who tear a meniscus state that they felt a “pop” in the knee when the injury occurred. Some individuals may be able to walk or continue athletic competition after tearing a meniscus. However, over the next two to seven days the individual will experience stiffness and swelling of the joint, often associated with joint pain, a “catching or locking” of the joint as the torn meniscus changes location within the joint, and or a reduced range of motion of the knee joint.

Diagnosis and Treatment of a Meniscus Tear

A complete physical exam of the knee joint, including manipulation of the knee joint in order to determine range of motion, is essential in the diagnosis of a meniscus tear. Following the physical exam the knee typically will be imaged — either by x-ray, MRI (magnetic resonance imaging), or arthroscopic examination of the knee.

Treatment of a meniscus tear ranges from conservative to aggressive treatment. Conservative treatment is termed “wait and see” treatment, involving rest, icing of the knee, and OTC (over the counter) pain medication. More aggressive treatment would involve physical therapy to strengthen the muscles around the knee joint, thereby helping to stabilize the knee during movement. The most aggressive treatment involves surgery of the affected joint.

Surgical treatment may involve one of three possible procedures.

Repair of the meniscus involves suturing the torn pieces of fibrous cartilage together so that the meniscus may repair itself. However, because fibrous cartilage is avascular, an average of 10% of attempted meniscus repairs are successful.
Trimming the meniscus involves removing the damaged segment of the meniscus and retaining the healthy, undamaged segment of the meniscus. Following this type of surgery physical therapy is typically required in order to strengthen the muscles surrounding the knee joint. This allows compensation for the reduced movement of the meniscus during movement of the knee, as well as the reduced cushioning of the knee joint by the meniscus.
Complete meniscectomy, which involves removal of the entire damaged meniscus, is typically the last surgical option and is only done when the meniscus is too damaged for either of the other two options.

Recovery from meniscus repair takes longer than meniscectomy — be it partial or total meniscectomy. It is not uncommon for complete recovery from meniscus surgery to take up to three months. During this time the patient will be recommended to initially utilize crutches in order to keep as much stress off of the affected knee as possible. OTC or prescription pain medications may be recommended, as well as physical therapy, followed by at-home rehabilitation exercises.

Although it is rare, individuals who have had surgery to repair their meniscus may experience increased stiffness of the joint, or even arthritis of the joint later in life. However, if the meniscus was severely damaged, the quality of life in the majority of patients following meniscectomy is significantly better than the quality of life without surgical meniscectomy.

Key Terms

Avascular - Lack blood vessels

Medial and lateral condyles of the femur - Anatomical structures that make up the majority of the distal portion of the femur

Patella - A large sesamoid bone enclosed within the patella tendon

Trimming the meniscus - Removing the damaged cartilage of the meniscus and retaining the healthy, undamaged cartilage within the knee joint

Passive locking of the knee joint - When the knee extends to its maximum range — with the foot fixed in position, such as when it is planted on the ground — the medial condyle of the femur rotate medially on the tibial plateau. This movement passively “locks” the knee into position.

Flexion - Any movement that decreases the angle of a joint.

Passive unlocking of the knee joint - Extension of the knee, with the foot fixed in position, starts with a lateral rotation of the medial condyle of the femur on the tibial plateau, passively “unlocking” the knee.

Complete meniscectomy - A surgical procedure that involves removal of the entire damaged meniscus.

Meniscus - A piece of fibrous cartilage found within the knee joint. This structure cushions the joint and deepen the articulating surfaces of the tibial plateau.

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