Fibrocartilage is a type of connective tissue that provides structural support within the musculoskeletal system. It is a unique hybrid, combining the toughness of fibrous tissue with the elasticity of cartilage. This tissue acts as a durable, flexible shock absorber in various parts of the body, managing compressive forces and reducing stress on joints. Its distinct composition allows it to withstand significant mechanical stress while maintaining some degree of flexibility.
Composition and Structure of Fibrocartilage
Fibrocartilage is primarily composed of a dense network of strong Type I collagen fibers, which provide impressive tensile strength. These fibers are interwoven with a matrix rich in proteoglycans, a characteristic feature also found in hyaline cartilage, which contributes to its cushioning properties. The tissue also contains both chondrocytes, the cells that maintain cartilage, and fibroblasts, cells typically found in fibrous connective tissue. This unique blend of components gives fibrocartilage its resilient qualities. This intricate structural arrangement explains why fibrocartilage is exceptionally tough and capable of enduring high mechanical loads.
Location and Function in the Body
Fibrocartilage is strategically located in several areas throughout the human body where strong support and shock absorption are needed. Its presence helps distribute forces and stabilize joints.
Menisci
In the knee, fibrocartilage forms the menisci, two C-shaped pads that sit between the thigh bone and shin bone. These menisci act as shock absorbers, distributing weight across the joint and contributing to knee stability during movement.
Intervertebral Discs
The intervertebral discs found between the vertebrae of the spine also contain fibrocartilage. The outer ring of these discs, known as the annulus fibrosus, is primarily composed of fibrocartilage. This structure provides cushioning between spinal bones and protects the spinal cord from compressive forces.
Pubic Symphysis
The pubic symphysis, a joint connecting the left and right pubic bones in the pelvis, is another location for fibrocartilage. This joint allows for slight movement and provides stability to the pelvic girdle.
Temporomandibular Joint (TMJ) Disc
The temporomandibular joint (TMJ) disc, located in the jaw, also contains fibrocartilage. This disc facilitates smooth and stable movement of the jaw.
Common Injuries and Healing Challenges
Fibrocartilage, despite its resilience, is susceptible to injury from acute trauma or degenerative wear over time. Common injuries include meniscal tears in the knee, often resulting from twisting motions or direct impact. Intervertebral discs can also suffer damage, leading to conditions like herniated discs, where the fibrocartilaginous outer layer ruptures, allowing the inner material to bulge.
A significant challenge with fibrocartilage injuries is their limited capacity for self-repair. This is primarily due to its avascular nature, meaning it has a very restricted blood supply. Without a robust blood supply, fibrocartilage struggles to initiate and complete a healing process on its own. Many tears, particularly those in the central regions of structures like the meniscus, lack any direct blood flow, rendering them unable to heal. While some peripheral tears might have a minimal blood supply allowing for some repair, the overall lack of vascularity means that most significant fibrocartilage damage does not heal effectively without intervention. The body may form a less organized fibrous scar tissue in response, which does not possess the same biomechanical properties as the original fibrocartilage.