Osteoarthritis is a disease that breaks down cartilage, the soft tissue that cushions your joints. Without protection between them, bones rub together and the symptoms of osteoarthritis appear.

Osteoarthritis is the most common type of arthritis. It affects an estimated 27 million Americans age 25 and older; nearly half (12 million patients) are at least 65 years old.⁴ Before age 45, more men than women have osteoarthritis. After age 45, the disease is more common in women, probably because adult women’s hips tend to be broader than men’s, which puts more long-term stress on their knees. As the population ages, the number of people with osteoarthritis is projected to increase because the main risk factors (e.g., advanced age and obesity) will be more common.

Osteoarthritis has significant personal, health, and economic costs:

• About 80% of patients with osteoarthritis have some degree of movement limitation
• 25% cannot perform major activities of daily living
  
• 11% of adults with knee osteoarthritis need help with personal care
• 14% require help with routine needs
  
• 40% of adults with knee osteoarthritis reported their health “poor” or “fair”
• Adults with knee osteoarthritis miss nearly 3 weeks of work (13 days) each year.

Every year, around 400,000 patients with osteoarthritis are hospitalized for knee and hip replacements. These account for 55% of all arthritis-related hospitalizations and cost nearly $8 billion. As of 2004, medical costs associated with all forms of arthritis exceeded $86 billion.

Pain is probably the most important factor affecting quality of life in osteoarthritis patients. Inadequate treatment of osteoarthritis pain can have serious health consequences, including decreased immune function, slow wound healing, anxiety, and depression.