Articular cartilage covers joint surfaces and acts as a shock absorber and cushion between the joints. Injury to this smooth tissue is not uncommon and can be the result of either a traumatic event or general wear and tear. Traumatic articular cartilage injuries are common in those who lead active lifestyles, and are frequently due to a forceful blow to the joint, such as a sudden fall onto a hard surface. Injuries due to general wear and tear are often the result of the softening of tissue and eventual loss of cartilage function.
Traumatic or degenerative causes are generally responsible for articular cartilage injuries. Traumatic mechanical destruction is most commonly caused by a direct and forceful blow to the joint that may damage the cartilage by itself, or both the cartilage and the underlying bone. A chondral fracture is an example of damage to the cartilage without a breaking of the bones. This type of fracture is due to a trauma to the joint surface that forces the bones to slide across each other with excessive force.
Osteochondral fractures are also a form of traumatic mechanical destruction, as they are frequently the result of direct trauma to the joint. When the joint suffers an uncommonly hard blow, cartilage may break off, pulling away a piece of bone in the process. Known as a loose body, this small piece of cartilage and bone can float inside the joint, causing irritation and locking of the surrounding tissue and joint.
Many degenerative articular cartilage injuries were once considered a symptom of aging, but are now thought to occur in people of nearly any age. Osteoarthritis, or degenerative joint disease, is one example. This condition is characterized by a progressive loss of cartilage, followed by the destruction of the underlying bone. Although the exact cause of osteoarthritis is unclear, many feel that things like abnormal joint anatomy or high-impact twisting injuries may factor into the development of this condition.
Chondrosis, or chondromalacia, is another form of progressive mechanical degeneration. This condition is defined by a gradual softening of the articular cartilage. The degree of degeneration is often divided into four types: softened, fissured, crab meat-like, and exposed bone. Although this condition is considered progressive, its cause can generally be traced back to any number of articular cartilage injuries.
