Osteoarthritis is the most common form of arthritis and joint disease, affecting older adults over age 45, especially women. It occurs when the cartilage cushioning the bones in joints deteriorates, causing pain, stiffness, swelling, and loss of flexibility. Risk factors include age, sex, obesity, joint injuries, repeated stress, genetics, and certain diseases. While it cannot be reversed, treatments focus on reducing pain and improving mobility through medications, physical therapy, injections, and sometimes surgery.