Arthritis nearly always causes joint pain (also called arthralgia), though not all joint pain is due to arthritis. The pain of arthritis is usually described as a dull, deep or aching. Burning or stabbing pains are rarely due to arthritis and should raise the possibility of some other condition such as nerve injury or even vascular problem. While there are more than 100 types of arthritis, Osteoarthritis (OA) and Rheumatoid Arthritis (RA) are among the most common. OA and RA demonstrate well the differences between "non-inflammatory" and "inflammatory" arthritis.
When there is significant inflammation, as seen in Rheumatoid Arthritis, symptoms tend to be worse in the morning. In fact, morning stiffness lasting one hour or longer is part of the "classification criteria" used for enrolling patients in RA studies. There is often warmth, swelling and marked limitation of motion. Those with RA typically suffer with multiple inflamed joints, often more than 10 that affect the both sides of the body in roughly the same way and nearly always involving the hands and wrists. The classic RA patient is female with symptoms commonly beginning between the age of 25 and 45.
Osteoarthritis is known as the "wear and tear" arthritis associated with past injury or aging. Joint pain in OA tends to be mostly use-related. Marked swelling is less common and only a few joints tend to be involved, particularly the hips, knees, hands and spine. The typical OA patient is older than age 50, or has had multiple injuries, as may be the case for a competitive athlete.
The pattern of symptoms, age and gender of the person enduring joint pain helps doctors distinguish between RA and OA. In addition, symptoms outside the joints, such as skin nodules, eye inflammation or lung disease that may be associated with RA (but not OA) and selected tests (such as blood tests and x-rays) may also be helpful. In most cases the diagnosis of RA is largely clinical, meaning that doctors must rely on the pattern of symptoms and physical examination results to establish the diagnosis.

Following a diagnosis of RA or OA, the course of the arthritis is highly variable. Some with OA do very well over time by simply taking acetaminophen, while others gradually worsen no matter what they take. The patients who do not improve with oral medications may eventually need joint replacement surgery. For RA, the arthritis course is even more variable. Some mild forms require supportive care, while others may require multiple medications to maintain functionality. Certain features, such as the presence of an antibody called the rheumatoid factor, can help doctors predict the arthritis may become more severe. It is remarkably difficult to predict how an individual will do, particularly because response to therapy is highly variable. If untreated, RA can lead to joint damage and disability. This is by no means universal, and mild forms may be under appreciated.