Fibrocartilage is a type of cartilage which is very rich in type I collagen, and found in areas such as the meniscus of the knee, the pubic symphysis, and the vertebral discs. This type of cartilage is especially strong and durable, so it appears in areas where these traits are needed. It can injure in the form of tearing, with surgery often being required to repair a tear of fibrocartilage or to stabilize the area where the tear occurs so that healing can take place.
This form of cartilage is characterized by the bundles of tough collagen which are clearly viewable under a microscope when it is examined. The bundles are interspersed with clefts which contain cartilage cells, and the cartilage includes a mixture of types I and II collagen, along with other components of cartilage. The bundles of collagen are part of what makes fibrocartilage so tough; while individual strands may break, others will retain their strength and supportive structure to keep the cartilage from being compromised.
Along the spine, fibrocartilage is needed to create padding between the vertebrae while also offering some protection to the spinal cord. Having a jointed spine is what allows organisms to bend, but it also creates vulnerability at each joint. Fibrocartilage supports the spine and the joints of the spine, absorbs shocks, and creates a surface for articulation so that the vertebrae can move smoothly when someone bends or twists the spine.
In the public symphysis, the cartilaginous joint which comprises part of the pubic bone, fibrocartilage holds the joint together, but it can also soften and pull apart during pregnancy to allow the expanding uterus to fit. During labor and delivery, it pulls apart even further so that the baby can get out, before firming back up again after pregnancy to stabilize the pelvis. This softening occurs in response to the release of a hormone known as relaxin.
In joints such as the knee, fibrocartilage is involved in the articulation of the joint while also protecting the joint. This type of cartilage appears in several other joints which see a lot of use and may be subjected to heavy impacts, because it is less prone to tearing and separation than other forms of cartilage. Problems with the cartilage in a joint can lead to issues such as pain and soreness in the joint, stiffness, and eventual damage to the bone as the padding of cartilage is worn away.