Causes and incidence of Osteoarthritis
Osteoarthritis (OA) is the commonest cause of joint disability in developed world, and listed in the top 10 of the global disease burden according to the World Health Organisation.
In white North Americans and North Europeans, about one-third of adults between 25 to 74 years have signs of osteoarthritis on their x-rays in at least one joint. In the US, 6% of those over 30 and 12% over 65 have a troublesome osteoarthritis knee.
Most common areas to be affected by OA are the hands, followed by feet, knees and hips. See Development of Osteoarthritis for a more technical account of the condition.
Risk factors for Osteoarthritis
Key risk factors are genetic, non-genetic and environmental
Risk factors are complex and may vary both from joint to joint and even within certain areas of one joint.
Age is the strongest risk factor for OA and the rates of arthritis for all joints rises with increasing age. Why age is important in OA is not clear. Aging joint cartilage may undergo chemical changes which render it vulnerable to the development of OA but there is no good evidence for this.
Women are at higher risk of developing OA than men, especially after the menopause but the reasons for this are complex and not well understood.
Obesity is strongly associated with knee (and to a lesser extent hip) OA, perhaps due to the increase in stress put through the joint when the person is overweight. However, systemic factors may be involved because obesity is linked to hand OA too.
Occupations and sport are also associated with developing OA. Jobs which involve kneeling, squatting and stair climbing are connected with higher rates of knee arthritis. Heavy repetitive joint use appears to increase OA risk.
Jobs involving repetitive heavy lifting (eg farming) show higher rates of hip arthritis.
Sport participation is connected with lower limb arthritis. Jogging, however, does not seem to increase the risk of OA if the person’s joints are normal.
Joint deformities, knee mal-alignment, joint laxity (loose ligaments), changes in walking pattern and quadriceps muscle weakness are all associated with OA knee.