**2. Primary osteoarthritis**

Primary OA is a chronic degenerative condition of mobile joints due to an unknown cause. This may result due to aging because few people do not show any clinical or functional signs of the diseases in the late 90s. The proteoglycan and water content of the cartilage reduce with the advancement of age, hence the toughness of cartilage and increasing the susceptibility of collagen fibers to degenerate [8]. Mild inflammation around the joint capsule may occur in OA as compared to rheumatoid arthritis. This inflammation is in response to the small particles of the debris produced by this cartilage breakage and then attempted clearance by the scavengers cells located in joint lining [8]. New bone outgrowths called 'spurs' or osteophytes may form on the margins of the joint, possibly in an attempt to improve the congruence of the articular cartilage surfaces. Some of these bone changes, along with low-grade inflammation, may cause pain and mobility.
