There are at least 100 different types of arthritis and related diseases (Source: AF). Of these, osteoarthritis (OA) and rheumatoid arthritis (RA) are the most common. OA is more common than RA, but both diseases together affect millions of Americans and are the main cause of disability in the United States (Source: CDC). How Are Osteoarthritis and Rheumatoid Arthritis Similar? OA and RA share similar symptoms and treatments. Symptoms: Both OA and RA cause joint pain, swelling and stiffness. These symptoms often result in limited range-of-motion and movement of your joint. Treatments: Some of the basic treatments for OA and RA are the same. If you have either type of arthritis, you will benefit from medicines and other treatments aimed at decreasing pain and inflammation and maintaining joint function. For example, both diseases respond to lifestyle changes and anti-inflammatory medicines. However, RA often requires additional medications to control your immune system. These medicines include disease-modifying anti-rheumatic drugs (DMARDS) and biologic response modifiers (BRMs). How Are Osteoarthritis and Rheumatoid Arthritis Different? Although they are both forms of arthritis, OA and RA are different diseases with different disease processes. Osteoarthritis is the result of wear and tear on your joints with time. OA causes your joint cartilage to deteriorate. Your body often responds by growing bone spurs or bone overgrowths. Rheumatoid arthritis is an autoimmune process where your immune system attacks its joint connective tissue. As a result, cartilage and protective membranes become inflamed, swollen and may be permanently damaged. Other differences between OA and RA include: Symptoms: While OA and RA share common symptoms—joint pain, swelling and stiffness—in RA, you may also have constant fatigue, poor appetite, and a low-grade fever. Affected joints: Another difference between OA and RA is their joint pattern. RA is symmetric and usually affects the same joints on both sides of your body, such as both wrists. OA is not symmetric and may only affect a joint on one side of your body. For example, you can have OA in one hip joint and not the other. Risk factors: The main risk factor for OA is aging. The older you are the more likely you are to get OA. OA is also more likely if you’re overweight, you’ve injured a joint in the past, or you have a family member with OA. On the other hand, RA is more likely to develop in younger women between the ages of 30 and 60 years.There is not a strong genetic influence in RA, although both genetic and environmental factors play a role in your chance of developing the disease. Osteoarthritis and Rheumatoid Arthritis: Is It Possible to Have Both? It is possible to have both OA and RA. A previous joint injury can lead to both diseases, but OA is more likely to develop as you age. Likewise, as people with RA age, they are at risk of getting OA. This is called superimposed OA. It’s also possible to have elderly-onset RA when you already have OA. Elderly-onset RA is defined as RA that begins in people older than 60. How Will My Doctor Know Which Type of Arthritis I Have? Your doctor can determine which type of arthritis you have by looking at the pattern of joint involvement—in RA, joints on both sides of your body will be affected—and your risk factors (age, weight, past injury, family history). Your doctor also uses blood tests, joint fluid tests, and X-rays to properly diagnose your form of arthritis.