What is osteoarthritis?
Osteoarthritis is a degeneration of the cartilage of the joints without infection or particular inflammation. However, there are forms with an inflammatory component and many patients have sporadic flare-ups. This degeneration leads to a more or less rapid destruction of the cartilage which coats the ends of the bones. Anatomically, this destruction is accompanied by a bone proliferation under the cartilage.It is the most common joint disease. The first symptoms usually appear from 40-50 years, but the disease often starts much earlier in life.
Mechanisms of osteoarthritis
The articular cartilage is not an inert tissue: it is the seat of an intense activity where the production of chondrocytes (cartilage cells) is opposed, at least at the beginning, to the destruction of these same cells. When the phenomena of destruction prevail over the cartilaginous regeneration, the cartilage thickness decreases and the joint deteriorates definitively.This intense production activity of new cells is manifested, at the margin of the joint, by the new production of bone growths: osteophytes.
During cartilage destruction, small pieces of cartilage can become detached and "float" in the joint pouch: they then trigger mechanical inflammatory attacks that result in hypersecretion of fluid and swelling of the joint.
Osteoarthritis is characterized by three anatomical lesions:
- Achievement of articular cartilage that cracks and grows ulcerations (holes in the cartilage) that can leave the bone bare;
- Achievement of the bone itself, which decalcifies in some places ( osteoporosis ) and condenses in others, especially in the area near the joint in the pressure zones: it is osteosclerosis under chondral;
- The formation on the edges of the joint of small bone growths: osteophytes (sometimes called "parrot beaks" because of their radiological form).
Causes and risk factors of osteoarthritis
In osteoarthritis, the destruction of the cartilage corresponds to a cracking of the surface towards the depth of the cartilaginous tissue. This cracking is related to mechanical phenomena, but it is also favoured by biochemical alterations of the cartilage structure.Schematically, we can consider that osteoarthritis is the result:
- Abnormal physical stresses on normal cartilage;
- Normal physical stresses on abnormal cartilage;
- From the conjunction of the two previous situations.
- General: age, weight, menopause, other rheumatism.
- Genetics: the concept of familial osteoarthritis is well proven for arthrosis of the knee, hip and hand;
- Local :
- Significant or repetitive trauma (hard work, violent sports, meniscus lesions ...);
- Abnormal position of the joint (scoliosis, malformation of the hip, ...);
- Other localized bone or joint diseases (sequelae of arthritis, sequelae of fractures, Paget's disease ...).
Screening for congenital joint abnormalities, followed by a correction in childhood, is of paramount importance to prevent the onset of painful osteoarthritis in adulthood.
Obesity (or simple overweight) is undoubtedly a factor favouring the appearance of osteoarthritis in the hips and especially the knees.
To learn more, read our article on risk factors for osteoarthritis.
The symptoms of osteoarthritis
Signs of osteoarthritis vary with the joint concerned. However, in all cases, the main reason for consultation is pain associated with functional impairment.The pain is, in principle, called "mechanical" because it has the following characteristics:
- It is triggered and aggravated by movement;
- It stops or lessens more or less completely when the joint is at rest;
- It is less important in the morning, then increases during the day and is highest in the evening;
- It hinders falling asleep, but can also lead to nocturnal awakenings (about 50% of osteoarthritis patients are woken at night by their pain);
- It reappears each time the affected joint is subjected to lot of pressure: walking for osteoarthritis hip, climb a stair for the knee, lift the arm for the shoulder etc.
The osteoarthritic joints are, in principle, neither red nor hot. They can be swollen when a fluid effusion (effusion of synovium) is established, which is particularly common in the knees. However periods of inflammatory growth exist and there would be an inflammatory component in this disease, different and less important than that of rheumatoid arthritis.
In the long run, osteophyte bone growths cause deformities of the joints, especially visible in the hands and knees.
The general condition of the patient is always good. There is no fever or weight loss.
Osteoarthritic lesions are irreversible and lead, in addition to deformities, to articular stiffening that can progress to partial impotence.
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