<s>[INST] Arthritis is just achy joints, right? [/INST] Essentially, yes. Arthritis literally means "inflammation of a joint"—the place where two bones connect, according to the American Academy of Orthopaedic Surgeons. There are more than 100 different types of arthritis, but osteoarthritis, which we'll address in this article, is the most common, affecting nearly 27 million Americans, almost 60% of whom are women. In osteoarthritis, cartilage—the slippery tissue that protects the ends of your bones in the joint—gradually wears down. This can make your knees feel achier than usual after you work out or leave you feeling stiff and old lady-ish when you climb out of bed. No one knows exactly what causes this cartilage breakdown, but a combination of factors like aging, joint injuries, genetic tendencies, and obesity, are all thought to play a role, says the Mayo Clinic. Source: Prevention. Link: https://www.prevention.com/health/a20469909/answers-to-your-arthritis-questions/. Field: Rheumatology. Disease: Arthritis </s>