Fibrocartilage: Structure, Function and Conditions

What is Fibrocartilage?

Fibrocartilage (Latin: Fibrocartilago) is one of the three types of cartilage found in the human body, alongside hyaline cartilage and elastic cartilage. It is characterized by a high concentration of type I collagen fibers, which provide its distinctive toughness and tensile strength. Compared to other cartilage types, fibrocartilage contains less ground substance (matrix) and more densely packed collagen fiber bundles arranged in parallel or interwoven patterns.

Fibrocartilage represents a transitional tissue between dense connective tissue and hyaline cartilage, making it ideally suited for structures subjected to both compressive and tensile forces.

Location in the Human Body

Fibrocartilage is found at several key locations throughout the body:

• Intervertebral discs: The annulus fibrosus of the spinal discs is composed of fibrocartilage, protecting the nucleus pulposus from excessive pressure.
• Knee menisci: The crescent-shaped menisci consist of fibrocartilage and serve as shock absorbers and pressure distributors within the knee joint.
• Pubic symphysis: The junction between the two pubic bones is stabilized by a fibrocartilaginous disc.
• Articular labra: At the hip (acetabular labrum) and shoulder (glenoid labrum), fibrocartilage deepens the joint socket and enhances stability.
• Tendon and ligament insertions: Fibrocartilage commonly occurs at entheses, the transitional zones where tendons and ligaments attach to bone.

Structure and Composition

The microscopic structure of fibrocartilage differs significantly from other cartilage types:

• Type I collagen: The dominant component, responsible for high tensile strength.
• Type II collagen: Present in smaller amounts, typical of hyaline cartilage.
• Chondrocytes: Cartilage cells are often arranged in rows or small clusters between collagen fiber bundles.
• Proteoglycans and water: Present in lower quantities than in hyaline cartilage, which accounts for fibrocartilage being less elastic.

Fibrocartilage generally lacks a perichondrium (cartilage membrane), which limits its regenerative capacity.

Function

The primary functions of fibrocartilage in the human body include:

• Shock absorption: Cushioning mechanical loads, for example in the knee joints during walking or running.
• Pressure distribution: Even distribution of body weight and force across joint surfaces.
• Tensile resistance: Withstanding pulling forces at tendon and ligament attachment sites.
• Joint stabilization: Improving the mechanical stability of joints and the spine.

Clinical Relevance and Conditions

Damage to fibrocartilage is clinically significant because its regenerative capacity is limited:

Meniscus Tear

A meniscus tear is a common sports injury in which the fibrocartilage of the meniscus is torn. Depending on the extent and location of the tear, treatment may range from conservative management to surgical repair (meniscus suture) or partial removal (meniscectomy).

Intervertebral Disc Herniation

Disc herniation (nucleus pulposus prolapse) occurs when the gel-like core of the intervertebral disc pushes through the fibrocartilaginous annulus fibrosus, potentially compressing adjacent nerves. Symptoms include back pain, numbness, and in severe cases, motor weakness.

Symphysis Pubis Dysfunction

Particularly during pregnancy, the fibrocartilage of the pubic symphysis can become overstretched or damaged, a condition known as symphysis pubis dysfunction, causing significant pelvic pain.

Labral Tear

Labral tears at the hip or shoulder commonly result from overuse or trauma and can cause pain and joint instability.

Diagnosis

The following diagnostic methods are used to evaluate fibrocartilage structures:

• Magnetic Resonance Imaging (MRI): The gold standard for visualizing menisci, intervertebral discs, and labra; allows precise assessment of tears and degenerative changes.
• Ultrasound: A complementary method, particularly useful for superficially located structures.
• Arthroscopy: Direct visualization and potential surgical treatment of fibrocartilage damage within a joint.
• X-ray: Used indirectly to assess joint space narrowing and bony involvement.

Treatment

Treatment of fibrocartilage injuries depends on the type, location, and severity of the damage:

• Conservative treatment: Physiotherapy, pain management, rest, and targeted strengthening exercises.
• Surgical treatment: Arthroscopic repair, partial resection, or reconstructive procedures.
• Stem cell therapy and tissue engineering: Modern, still largely experimental approaches aimed at regenerating fibrocartilage tissue.

References

1. Junqueira, L.C., Carneiro, J. (2005). Basic Histology: Text and Atlas. McGraw-Hill, New York.
2. Buckwalter, J.A., Mankin, H.J. (1998). Articular cartilage: degeneration and osteoarthritis, repair, regeneration, and transplantation. Instructional Course Lectures, 47, 487-504.
3. Bhosale, A.M., Richardson, J.B. (2008). Articular cartilage: structure, injuries and review of management. British Medical Bulletin, 87(1), 77-95.