Osteoarthritis has for a long time been considered to be a degenerative disease, characterised by worn cartilage in the joints, leading to irreversible lesions. But recent studies have highlighted a major inflammatory component associated with osteoarthritis. Nowadays it is classified as a separate disease of the joints.
Frequently associated with ageing, in reality osteoarthritis can occur at any age. Joint pain, loss of flexibility and mobility… osteoarthritis is the most common rheumatoid disease in France, representing the second biggest cause of disability.
Osteoarthritis: it concerns us all!
Osteoarthritis is the most widespread joint disease affecting 17% of the French population, some 10 million people. It is estimated that by 2030 it could even affect up to 22% of the French!
Patient treatment costs are also constantly increasing, with 3.5 billion euros spent in 2010 against just 1 billion euros in 1993.
Contrary to popular belief, osteoarthritis does not only effect the elderly! For a long time considered to be an inevitability associated with ageing, although its occurrence increases with age the disease affects all generations.
The figures bear this out: osteoarthritis affects 65% of the over 65s and 80% of the over 80s, but also 3% of those under 45.
A localised ailment
Although osteoarthritis can affect all the joints, certain locations are much more frequently affected than others. The shoulders, elbows, wrists and ankles are in fact rarely affected whereas the spine, knees, hands and hips are the favoured targets.
The target of osteoarthritis - the cartilage
Osteoarthritis is a disease affecting the cartilage that covers the bones of the joints (to find out about the composition of our joints, consult our well-being file).
This cartilage has unique mechanical properties enabling it to resist pressure and deformation throughout the host's lifetime without incurring damage.
This tissue constantly renews itself thanks to specialised cells, the chondrocytes, via the neo-synthesis of the components of the extracellular matrix of the cartilage.
Such renewal requires a perfect equilibrium of chondrocytes between matrix destruction and production, which is vital for healthy cartilage.
What happens when osteoarthritis occurs?
Osteoarthritis is characterised by different types of damage:
Lesions form in the cartilage, its thickness diminishes, it cracks and ultimately disappears. The joint is then damaged irreversibly.
Erosion of the cartilage produces tiny fragments which come free in the joint capsule. They trigger inflammation of the synovial membrane and secretion of liquid, leading to swelling.
The reduced thickness of cartilage brings the bone surfaces of the joints closer together, and finally into direct contact (joint space narrowing), leading to wear via friction: the bone is damaged. This causes sometimes painful functional discomfort and even loss of joint mobility.
Under the effect of the pressure exerted by space narrowing, bone excresence forms on the edges of the joint, the osteophytes (sometimes called 'parrot's beak' due to their appearance during radiography). They are responsible for the joint deformation frequently observed in the hands.
The inflammation at the heart of osteoarthritis
Osteoarthritis has long been considered to be a non-inflammatory degenerative disease. Yet recent studies have shown that behind the destruction of cartilage and the pain there is actually a hidden inflammatory component that plays an important role.
Inflammation is a normal reaction mechanism of the body that combats aggression. Most of the time it eliminates viruses or bacteria by producing so-called pro-inflammatory molecules, the cytokines.
Osteoarthritis is caused by "abnormal" inflammation of the chondrocytes under the impact of trauma (repeated demands on the joints, sport, impact, manual work...) but also by genetic predisposition and environmental factors that are still not fully understood.
Inflamed chondrocytes produce pro-inflammatory cytokines that spread throughout the joint (cartilage, synovial fluid and synovial membrane), disrupt the synthesis of cartilage matrix and cause pain.
The chondrocytes also synthesise enzymes, notably the collagenases, which digest and destroy cartilage. The balance is disrupted: destruction overwhelms the formation of cartilage.
A genuine vicious circle is established with this inflammatory process as the lesions caused by the destruction of cartilage maintain the inflammatory state of the joint.
Where does the pain come from?
Pain from osteoarthritis is not directly related to the damage in the cartilage as it does not contain any nerves. It does in fact come from structures located nearby such as bone, the synovial membrane and also the tendons and ligaments.
In fact, inflammation invades the surrounding tissue and stimulates the nerve endings, which become hypersensitive.
Acidity is the great enemy of the joints! An acid environment promotes the worsening of joint lesions: to combat excess acid in the tissues, the body will call on its reserves of de-acidifying minerals. The alkali minerals of the bones and joints will therefore be sacrificed first, increasing the fragility of these tissues.
What are the solutions to combat osteoarthritis?
Currently there are no treatments for osteoarthritis that offer a cure. The available treatments are only symptomatic and are designed to soothe the pain. The first instinct is frequently to use analgesics followed by anti-inflammatories but they have multiple side effects, notably on the digestive system.
Other therapeutic approaches exist such as infiltrations of hyaluronic acid (viscosupplementation), or even surgery (joint washing) and the fitting of a prosthesis, but these are relatively invasive interventions.
Fortunately, there are natural compounds able to protect cartilage in order to delay such intervention and reduce the consumption of drugs (consult our well-being file...).
To find out more:
Website of the AFLAR (French Association for the Fight Against Rheumatism): www.aflar.org