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​What causes OA

30th August 2018

It can be difficult to define the causes of osteoarthritis, but there are a number of factors that can play a part in the development of the disease. The joints are constantly under stress through many aspects of normal life and damage can occur over time. Osteoarthritis occurs when the cartilage that protects the ends of the bones begins to break down. Instead of being firm and slippery, allowing the joint to move without friction, it can become rough and eventually wears down so that the bones rub against each other. This causes pain, problems with the mobility of the joint and swelling. Sometimes bony growths develop and the area becomes red and swollen.

Although the precise cause of osteoarthritis is not known, predisposing factors include injury to the joint, other conditions such as gout or rheumatoid arthritis, congenital abnormalities, age, family history and obesity. Secondary osteoarthritis can occur if the condition is caused by another disease or condition.

Joint injury

Injury to a joint can be caused by overuse, particularly by using the joint too soon following an operation or injury. Some sports injuries can be responsible for the development of osteoarthritis, even if the injury appears to have healed completely. Osteoarthritis can be more likely to occur in a joint years after an injury than in an uninjured joint. The knee joints are possibly the ones most commonly injured in sports and many athletes now opt to protect their knees by using a knee support even when no injury is present. Some sports such as skiing place massive stress on the knee joints and the sudden changes in direction combined with landing heavily on uneven slopes can cause joint injury. Repeated small stresses can also result in injuries to the weight bearing joints.

Other conditions

If a joint has been damaged previously by a condition such as gout or rheumatoid arthritis, osteoarthritis is more likely to develop. Gout causes crystals of uric acid to be deposited in the cartilage which causes degeneration of the cartilage and secondary osteoarthritis. In pseudo-gout, calcium pyrophosphate crystals have a similar effect. Diabetes and other hormone disorders can also play a part in the cartilage becoming worn early and osteoarthritis developing.

Congenital abnormalities

People are sometimes born with joints that are abnormally formed. This can lead to the joint being particularly vulnerable to damage through mechanical wear and tear so that the cartilage degenerates and is destroyed early. When osteoarthritis affects the hips, it is often related to a structural abnormality that the person has had since they were born.

Age

The risk of developing osteoarthritis increases with age. As a person grows older, the water content of their cartilage is increased and the protein in it begins to degenerate. Because the joints are subjected to repetitive use year after year, damage occurs to the cartilage and this can lead to swelling and joint pain. In time, the cartilage starts degenerating and it can flake or small crevasses form. If the condition is very advanced the protective cartilage between the bones may be lost causing friction between them This can cause limitations to the mobility of the joints and increased pain. When the cartilage is damaged, new bone growths known as bone spurs can begin forming around the joints.

Family history

Although no specific gene that causes osteoarthritis has been identified, the condition can sometimes appear to run in families. Sometimes multiple members of a family are found to have osteoarthritis, which makes it seem likely that there is a hereditary factor. A rare cause of this type of osteoarthritis may be defects in collagen. Collagen makes up an important part of cartilage and if it is defective, the cartilage can become worn early.

Obesity

Obesity is perhaps the factor that is most within the control of the individual and even when osteoarthritis is already present, the condition can be improved by losing weight and reducing the stress on the affected joints. There are several reasons why obesity contributes to the development of osteoarthritis. Firstly, carrying excess weight puts increased mechanical stress on the joints that bear the majority of the weight, in particular the hips and the knees. This, in turn, damages the cartilage so it does not give the ends of the bones the protection they need. The heavier a person is, the greater their risk of developing osteoarthritis. Another risk factor with obesity is the fact that proteins that can cause inflammation in and around the joints are produced in fat tissue so the less fat tissue a person has the better. Whilst ageing is the major significant risk factor for osteoarthritis, obesity closely follows it.

In addition to the risk factors already discussed, there are other factors that can increase an individual’s risk of osteoarthritis. Although it is not clear why, women are more likely to develop the condition than men.

Another factor that can play a part in osteoarthritis is a person’s occupation. If the individual has a job or undertakes activities that involve placing repetitive stress on a joint or joints, osteoarthritis may develop in that joint. A well-researched example of occupation affecting the joints is that of weight lifters who often develop osteoarthritis of the knees at an early age. This is believed to be due, at least in part, to their high body weight.

Footballers and military personnel also appear to develop osteoarthritis of the knees, which is thought to be the result of repeated trauma to the ligaments, cartilage and bones that make up the tissues of the joint. Although it would seem likely that long distance runners would also inflict repeated trauma on their knees, no health studies so far have identified any increased risk of the condition developing early in this group.

Managing osteoarthritis

Lifestyle changes can help with managing the pain and inflammation of osteoarthritis. Losing weight, exercising and changing your eating habits can often make the condition more manageable. Losing weight will naturally reduce the stress on the joints and can help, particularly with knee joints that are affected by osteoarthritis. A regular exercise programme will also help by keeping the joints more flexible and mobile but it is important to take advice from a health professional such as a physiotherapist or doctor so that you do not move a joint inappropriately or cause the condition to worsen.

Eating a healthy diet is important for everyone, but if you have osteoarthritis, recent research has shown that eating plenty of fruit and vegetables can help with reducing the pain and inflammation in the joints. This is because they contain antioxidants which protect against cell damaging free radicals that can affect the cartilage and synovium, as well as other tissues. An adequate intake of vitamin C is particularly important because it is needed in the development of cartilage.

If pain is a major problem medication can help and there are various options, including over-the-counter analgesics such as paracetamol, prescribed painkillers such as the opioids and topical preparations that are rubbed into the affected area. Non-steroidal anti-inflammatory drugs (NSAIDs) are also an option. These work by reducing inflammation in addition to easing pain. They include ibuprofen, aspirin, naproxen and celecoxib but are not suitable for everyone. If knee joints are affected by osteoarthritis, sometimes a support can help to stabilise the joint and reduce the pain of osteoarthritis, as well as prevent further damage that might occur.

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