In our daily lives and during our clinic sessions, we often encounter people who say they have arthritis. What exactly is arthritis? Arthritis is literally an inflammation of the joints. Inflammation here is a medical concept of inflammation, which is much broader than the general public’s understanding of the concept of inflammation by infection. In fact, it is not a single disease, but a collective term for a large group of diseases. Arthritis can involve just one joint or multiple joints. We can classify it by location as knee arthritis, hip arthritis, wrist arthritis, shoulder arthritis, etc. We can also classify it by whether the inflammation is infectious or not as infectious arthritis or non-infectious arthritis. Infectious arthritis can be divided into bacterial arthritis (including septic arthritis and tuberculosis arthritis caused by specific tubercle bacilli), fungal arthritis, and other infectious arthritis, depending on the causative agent. Non-infectious arthritis accounts for most of the arthritis. Many other diseases can cause secondary arthritis, such as immune diseases (including rheumatoid, lupus erythematosus, etc.), trauma (including intra-articular fractures and dislocations, etc.), congenital and hereditary diseases (such as acetabular dysplasia, hemophilia, etc.). However, primary osteoarthritis is the most common type of non-infectious arthritis and indeed all arthritis. The above mentioned so many various kinds of arthritis may be a bit confusing for the average person to see, I just do a simple actually still very incomplete introduction.