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What is Osteoarthritis of the Knee?

Affecting the knee joint, osteoarthritis of the knee is the second most common type of osteoarthritis after osteoarthritis of the spine. According to Arthritis Research Campaign, more than six million people in the UK have painful osteoarthritis in one or both knees. In 2006/2007, 62.150 primary knee replacements were performed in England and Wales, 97% of which were due to osteoarthritis.

Anatomy of the Knee

In order to understand how knee osteoarthritis develops, it helps to get a basic idea about knee anatomy and function.

The knee is the largest and one of the most complex joints in our body. Together with muscles, ligaments and other structures, the knee joint has to be able to deal with the impact of walking, running and jumping etc. The femur (thigh bone) comes together with the tibia (shin bone) to form our knee joint, which is protected by the patella (knee cap). Cartilage cushions the ends of the femur and tibia as well as behind the patella. Additional pads of cartilage called menisci protect the joint by absorbing shock during movement. Enveloping the knee joint is synovial fluid, which lubricates cartilage and keeps it smooth. Tendons attach muscles to the femur and tibia and help keep the joint in place. Four ligaments - medial collateral ligament, lateral collateral ligament, anterior cruciate ligament and posterior cruciate ligament - attach the joint bones to one another and provide stability and flexibility.

How does Knee Osteoarthritis Develop?

Knee osteoarthritis develops gradually over years. Arthritis Research Campaign explains that osteoarthritis of the knee typically develops in the cartilage under the patella (knee cap) or over the main surface of the joint. The surrounding bones grow thicker and bony spurs (outgrowths) may form. Often, excess synovial fluid is produced, which causes chronic inflammation and pain. In later stages, ligaments begin shrinking and the muscles around the joint weaken, making the knee joint unstable. In severe cases, the cartilage becomes so worn down that bone grinds against bone eventually causing deformity.

What are the Symptoms of Knee Osteoarthritis?

Knee osteoarthritis usually takes many years to develop and affects people differently. Most people experience knee pain in varying degrees of severity as well as stiffness in the joint, which tends to be worse after resting. Knee pain on the other hand, whether in the whole joint or just in a specific area, tends to be worse after physical activity. In cases of severe knee osteoarthritis, movement can be limited with the knee giving way.

What Causes Knee Osteoarthritis?

Scientists cannot pinpoint a specific cause(s) of knee osteoarthritis. However, certain factors appear to increase the risk of the condtion. These include:

• Age: The older we get, the higher our risk of knee osteoarthritis (usually after the age of 50 although it can develop at any age).
• Gender: Women are twice as likely to develop knee osteoarthritis as men and there seems to be a strong link to menopause.
• Weight: Being overweight puts extra stress on the knee.
• Genetics: Knee osteoarthritis is hereditary in some families and is due to a gene that affects collagen, a major constituent of cartilage.
• Excessive Exercise & Knee Injuries: Injury to ligaments or cartilage, particularly the menisci. Football players often injure their menisci, which increases the risk of knee osteoarthritis in the future.
• Knee Surgery: Knee surgery, especially to remove torn cartilage increases the risk of knee osteoarthritis significantly.

How is Osteoarthritis Diagnosed?

An x-ray and MRI are the best diagnostic tools together with a physical examination by the medical practitioner. Sometimes blood tests are also conducted to discard other types of arthritis such as rheumatoid arthritis.

How is Knee Osteoarthritis Treated?

• Painkillers and anti-inflammatory drugs (NSAIDs)
• Cortisone injections into the joint or around it
• Surgery to replace badly damaged joints
• Medical acupuncture
• Dietary supplements

Supportive devices for the Knee?

Many people with knee osteoarthritis find the use of supportive devices such as canes and knee supports/braces very helpful. Knee supports and braces are intended to provide stability and function of the knee and relieve some of the pressure from the joint. They also help to keep your knee correctly aligned and minimise pain.

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