Osteoarthritis is a degenerative joint disease that can affect any joint in the body, but it most commonly affects the hands, knees, hips, or spine. The disease occurs when the cartilage that cushions the ends of bones in the joints gradually deteriorates. Cartilage is a firm, slippery tissue that enables nearly frictionless joint motion. Eventually, if the cartilage wears down completely, bone will rub on bone, causing pain, stiffness, and swelling.

The exact cause of osteoarthritis is not known, but there are several factors that can increase the risk of developing the disease. These include:

• Age: The risk of developing osteoarthritis increases with age.
• Gender: Women are more likely to develop osteoarthritis than men, especially after age 50.
• Obesity: Extra weight puts more stress on joints, particularly weight-bearing joints like the hips and knees. This stress increases the risk of osteoarthritis in that joint. Obesity may also have metabolic effects that increase the risk of osteoarthritis.
• Joint injury or overuse: Injury or overuse, such as knee bending and repetitive stress on a joint, can damage a joint and increase the risk of osteoarthritis in that joint.
• Genetics: People who have family members with osteoarthritis are more likely to develop the disease.
• Bone deformities: Some people are born with malformed joints or defective cartilage.
• Certain metabolic diseases: These include diabetes and a condition in which your body has too much iron (hemochromatosis).

It is important to note that osteoarthritis is not caused by simple wear and tear on the joints, but rather by changes in the tissue that trigger the breakdown, which usually happens gradually over time.