Osteoarthritis (OA) of the knee is common, affecting approximately 10% of the population. It is most common in Women over the ages of 50 years and can affect one (unilateral) or both (bilateral) sides of the knee joint. The more commonly affected is the inner side of the knee also know as medial. Within a joint there is a very smooth fibrous connective tissue, known as articular cartilage. This covers the areas where each bone comes into contact with one another (articular surfaces). In a normal joint this articular cartilage allows for smooth movement within the joint as well as acting as a shock absorber. In addition to this cartilage is another tissue, known as the synovial membrane, which produces synovial fluid that lubricates the joint. Osteoarthritis (also called degenerative joint disease) is the degradation and degeneration of this articular cartilage. As the disease progresses, the cartilage itself becomes thinner and in some cases may wear away altogether.
In addition, the bones themselves become thicker and may form bony “spurs”. Associated with these changes is the inflammation of the synovial membrane or thin lining which surrounds the knee joint to keep the synovial fluid or lubrication in place. All of these factors can cause pain and impaired movement in the joint. Osteoarthritis can form in any joint but is more common in weight bearing joints such as the knee and hip.
The exact causes of osteoarthritis are unknown however there are a number of factors that are commonly associated with the onset of the disease.