Repairing the meniscus and articular cartilage
Meniscus
With the high forces sent through the knee, the meniscus may be torn. Only tears that have good blood supply can heal and be repaired. Repairs are often performed arthroscopically, requiring only small accessory incisions. Unfortunately, most meniscal tears cannot be fixed. These tears are treated by removing the torn portion in a procedure called a "partial meniscectomy." Removing the torn portion prevents the tear from aggravating the knee joint. However, repeated partial meniscectomies may result in a functional loss of the meniscal tissue and accelerate articular cartilage degeneration. In these cases, a meniscal allograft transplant may be necessary.
Articular Cartilage
There is a constant wear-out and replacement activity of the molecules that make up the articular cartilage matrix. Specialized cartilage cells, known as chondrocytes, are responsible for maintaining this matrix. Chondrocytes decrease in number as we age and can be damaged by repeated overuse (microtrauma) or single, high force impacts (macrotrauma). Once chondrocytes are damaged or lost, the surrounding matrix gradually degenerates and defects appear. Without intervention, the body is not able to repair these defects. In the majority of cases, there is very little cartilage tissue at the site available to repair; therefore, it must be restored or artificially replaced.
Open Reduction/Internal Fixation (ORIF)
Occasionally, a piece of cartilage may be displaced as a flap or loose fragment from the bone and adjacent cartilage. In some instances, it is possible to reattach the loose cartilage with sutures or screws and cartilage restoration is possible. This knee surgery is known as open reduction (the joint must be surgically opened to reduce the cartilage fracture) or internal fixation (the fixation method does not protrude through the skin).