Osteoarthritis is a chronic joint disorder that causes degeneration of joint cartilage and adjacent bone.  Cartilage acts as a cushion between the bone joints so when it breaks down, joint pain and stiffness result.

Osteoarthritis is the most common joint disorder.  Men and women are equally affected, but men tend to develop the disorder at an earlier age.  By age 40 many people have some evidence of the disease as seen on X-ray.  Osteoarthritis is classified as primary when the cause is unknown and secondary when the cause is another disease, such as Paget's disease, infection, deformity, injury or overuse of a joint.

Osteoarthritis may begin when the cells making up the cartilage don't function correctly.  The cartilage may experience overgrowth, then thin and develop cracks on the surface.  Cavities form in the bone beneath the cartilage which weakens the bone, bone ends may thicken, forming bony growths or spurs that interfere with joint movement and cause pain.  Finally, the smooth, slippery surface of the cartilage becomes rough and pitted to the extent that the joint can no longer move smoothly causing all the components of the joint to fall in various ways, altering the joint.