Arthritis is inflammation of one or more of your joints. Pain, swelling, and stiffness are the primary symptoms of arthritis. Any joint in the body may be affected by the disease, but it is particularly common in the knee.
Knee arthritis can make it hard to do many everyday activities, such as walking or climbing stairs. It is a major cause of lost work time and a serious disability for many people.
The most common types of arthritis are osteoarthritis and rheumatoid arthritis, but there are more than 100 different forms. While arthritis is mainly an adult disease, some forms affect children.
Although there is no cure for arthritis, there are many treatment options available to help manage pain and keep people staying active.
The knee is the largest and strongest joint in your body. It is made up of the lower end of the femur (thighbone), the upper end of the tibia (shinbone), and the patella (kneecap). The ends of the three bones where they touch are covered with articular cartilage, a smooth, slippery substance that protects and cushions the bones as you bend and straighten your knee.
Two wedge-shaped pieces of cartilage called meniscus act as “shock absorbers” between your thighbone and shinbone. They are tough and rubbery to help cushion the joint and keep it stable.
The knee joint is surrounded by a thin lining called the synovial membrane. This membrane releases a fluid that lubricates the cartilage and reduces friction.
The major types of arthritis that affect the knee are osteoarthritis, rheumatoid arthritis, and posttraumatic arthritis.
Osteoarthritis is the most common form of arthritis in the knee. It is a degenerative,”wear-and-tear” type of arthritis that occurs most often in people 50 years of age and older, but may occur in younger people, too.
In osteoarthritis, the cartilage in the knee joint gradually wears away. As the cartilage wears away, it becomes frayed and rough, and the protective space between the bones decreases. This can result in bone rubbing on bone, and produce painful bone spurs.
Osteoarthritis develops slowly and the pain it causes worsens over time.
Rheumatoid arthritis is a chronic disease that attacks multiple joints throughout the body, including the knee joint. It is symmetrical, meaning that it usually affects the same joint on both sides of the body.
In rheumatoid arthritis the synovial membrane that covers the knee joint begins to swell, This results in knee pain and stiffness.
Rheumatoid arthritis is an autoimmune disease. This means that the immune system attacks its own tissues. The immune system damages normal tissue (such as cartilage and ligaments) and softens the bone.
Posttraumatic arthritis is form of arthritis that develops after an injury to the knee. For example, a broken bone may damage the joint surface and lead to arthritis years after the injury. Meniscal tears and ligament injuries can cause instability and additional wear on the knee joint, which over time can result in arthritis.
A knee joint affected by arthritis may be painful and inflamed. Generally, the pain develops gradually over time, although sudden onset is also possible. There are other symptoms, as well:
During your appointment, your doctor will talk with you about your symptoms and medical history, conduct a physical examination, and possibly order diagnostic tests, such as x-rays or blood tests.
During the physical examination, your doctor will look for:
Your doctor may also recommend blood tests to determine which type of arthritis you have. With some types of arthritis, including rheumatoid arthritis, blood tests will help with a proper diagnosis.