The knee joint is the joint between the femur (thigh bone) and the tibia (shin bone). Its primary function is to support the weight of the body in both static (e.g. standing) and dynamic (e.g. walking or running) postures. It is a complex hinge joint.
The surfaces of the knee joint are covered in a lubricated low friction cartilage and the joint is made more stable by ligaments, tendons and muscles.
What is knee arthritis?
Arthritis is the wearing of the joint, which includes thinning and damage to the cartilage. As the protective cartilage is worn away, bare bone is exposed within the joint. Bony spurs and cysts also form. There are a number of different types of arthritis; the most common is osteoarthritis which is sometimes called ’wear-and-tear’ arthritis or degenerative joint disease. Rheumatoid arthritis and traumatic arthritis are also seen in the knee joint. Arthritis is the most common cause of chronic knee pain and disability.
Rheumatoid Arthritis is a disease in which the synovial membrane becomes thickened and inflamed, producing too much synovial fluid that over-fills the joint space. This chronic inflammation can damage the cartilage and eventually cause cartilage loss, pain and stiffness.
Traumatic Arthritis can follow a serious knee injury. A knee fracture or severe tears of the knee’s ligaments may damage the articular cartilage over time, causing knee pain and limiting knee function.
Osteoarthritis (OA) usually occurs after the age of 50 and often in an individual with a family history of arthritis. The cartilage that cushions the bones of the knee softens and wears away. The bones then rub against one another, causing knee pain and stiffness.
Osteoarthritis causes as much disability as cardiovascular (heart) disease.
What causes Knee Arthritis?
Several factors may increase the risk of developing osteoarthritis of the knee.
- Heredity: There is some evidence that genetic mutations may make an individual more likely to develop OA.
- Weight: Weight increases pressure on joints such as the knee.
- Age: The ability of cartilage to heal itself decreases as people age.
- Gender: Women who are older than 50 years of age are more likely to develop OA Knee than men.
- Trauma: Previous injury to the knee, including sports injuries, can lead to OA Knee.
- Repetitive stress injuries: These are usually associated with certain occupations, particularly those that involve kneeling or squatting, walking more than 2-4 km a day, or lifting at least 30 kilos regularly. In addition, occupations such as assembly line worker, computer keyboard operator, performing artist, shipyard or dock worker, miner and carpet or floor layer have shown higher incidence of OA Knee.
- High impact sports: Elite players in football, long-distance running and tennis have an increased risk of developing OA Knee.
- Other illnesses: Repeated episodes of gout or septic arthritis, metabolic disorders and some congenital conditions can also increase the risk of developing OA Knee.
- Other risk factors are being investigated, including the impact of vitamins C and D, poor bone alignment, poor aerobic fitness and muscle weakness.
What are the symptoms?
Pain is the most significant symptom. Patients may notice catching or grinding sensations. It is often difficult to “get going” when first standing up. Less commonly, others may notice that the patient’s legs are becoming bent.
In some people the pain may become so severe that it limits everyday activities, including walking, going up and down stairs, and getting in and out of chairs. Some patients may find it hard to walk more than a few blocks without significant pain and may need to use a cane or walker. Patients often complain of pain that is worse at night.
The knee may become stiff and unable to completely bend or straighten.
How is knee arthritis diagnosed?
Diagnosis is usually made on a history of symptoms of pain or disability and physical signs on clinical examination. Classic changes are seen in the joint on X-rays. An MRI may be ordered particularly in early cases of arthritis.
Can Knee Arthritis be treated without surgery?
There is no cure for arthritis. Initial treatment is generally conservative. Getting active and staying at a healthy weight are important for all patients with osteoarthritis of the knee. Exercise is a great way to improve health and is beneficial for those with osteoarthritis. Being active can help lessen pain and improve mobility. Walking, swimming, and water aerobics are good choices. Physiotherapy may help with flexibility and pain.
Some people may need to take pain medicine to help reduce pain and keep them moving.
There are a number of treatments on the market that usually do not help. These include glucosamine and chondroitin, joint lubricant injections and arthroscopic surgery. These treatments have been reviewed as part of a government funded review of the research and been found to be ineffective. More information is available if required, but the following points are noted.
Glucosamine and Chondroitin are nutritional supplements which claim to help build new cartilage. They are not regulated as drugs in Australia, so their quality may vary. They have a number of minor side effects including upset stomach, diarrhea, and headache. Although research studies show that more than half the people with osteoarthritis taking glucosamine and chondroitin improve, the same number of people who do not take the supplements also improve. This means that glucosamine and chondroitin are not the reason for improvement.
Joint lubricant injections involve three to five injections over a few weeks of a gel-like material into the knee joint. It is also called viscosupplementation and is not the same as cortisone injections. Many research studies have found that most people getting the shots do not have much improvement. This treatment has a number of side effects, some of which can be long term.
Arthroscopic surgery is an important procedure in a number of knee conditions but generally does not reduce the pain of knee osteoarthritis.
What operation may be beneficial?
There is no cure for arthritis. Surgical options include realigning (osteotomy) procedures or knee replacement (either partial or total)
In the arthritic knee, particularly in very young active patients who wish to return to contact sport or heavy manual labour, realigning the leg will put the body weight onto the normal side of the knee where the arthritis is minimal. This procedure does not cure the arthritis, but significantly decreases the pain associated with activity.
Knee replacement was first performed in 1968. Improvements in surgical materials and techniques since then have greatly increased its effectiveness. Approximately 30 000 knee replacements are performed each year in Australia.
Most patients who undergo total knee replacement are age 60 to 80. Recommendations for surgery are based on a patient’s pain and disability, not age. Total knee replacements have been performed successfully at all ages, from the young teenager with juvenile arthritis to the elderly patient with degenerative arthritis.