**1. Introduction**

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Osteoarthritis (OA) is described as a condition characterised by use-related joint pain experienced on most days in any given month, for which no other cause is apparent. OA is the commonest disease affecting synovial joints and affects more than 40% of the population over 65 years. It affects primary the knee joints however hip, ankle, shoulder and small joints of hand and feet may be involved.

Previously, OA was considered a wear and tear, degenerative disease that must be accepted as an inevitable consequence of trauma and ageing. With advances in research and understanding of the mechanism of OA progression it is now known as a disease of the synovial joint affecting subchondral bone, synovium, meniscus, ligaments and supporting structures around the joints, including the cartilage.

The pathological changes seen in OA are characterised by focal areas of loss of articular cartilage within the synovial joints, associated with hypertrophy of the bone (osteophytes and subchondral sclerosis) and thickening of the capsule. OA is a chronic, degenerative disease associated with joint pain and loss of function. The primary problem in OA is the damage to the articular cartilage, which triggers a series of other events that culminate in pain and loss/limitation of function in the affected joint.

Undoubtedly, pain, which is the most prominent and disabling presentation of OA, is an increasingly important public health problem especially within an increasing aging population.

## **2. Epidermiology**

OA occurs worldwide with higher prevalence in developed societies. Its twice as common in women as in men with a significant familial tendency.

The prevalence of OA increases with age in a progressive manner with 80% radiolographic changes in people by the age of 65 years. However only about 25-30% are symptomatic. Primary OA is uncommon before the age of 50 years.

World Health Organisation reports that knee OA is ranked fourth most important global cause of disability in women and the eighth most important in men. Annual arthroplasty rate in over the age of 65 in Europeans vary from country to country but are of the order of 0.5–0.7 per 1000. The annual costs attributable to knee OA are immense. There is therefore a burden on health from both morbidity and cost.

OA is a complex disorder with multiple risk factors.

### **2.1 Risk factors for OA**

