Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Osteoarthritis ?
    ### Response:
    Affects Many Older People Osteoarthritis is the most common form of arthritis among older people, and it is one of the most frequent causes of physical disability among older adults. The disease affects both men and women. Before age 45, osteoarthritis is more common in men than in women.
    