arthritides and the location. Rheumatoid arthritis is generally worse in the morning and associated with stiffness lasting over 30 minutes. However, in the early stages, patients may have no symptoms after a warm shower. Osteoarthritis, on the other hand, tends to be associated with morning stiffness which eases relatively quickly with movement and exercise. In the aged and children, pain might not be the main presenting feature; the aged patient simply moves less, the infantile patient refuses to use the affected limb. Elements of the history of the disorder guide diagnosis. Important features are speed and time of onset, pattern of joint involvement, symmetry of symptoms, early morning stiffness, tenderness, gelling or locking with inactivity, aggravating and relieving factors, and other systemic symptoms. Physical examination may confirm the diagnosis or may indicate systemic disease. Radiographs are often used to follow progression or help assess severity. Blood tests and X-rays of the affected joints often are performed to make the diagnosis. Screening blood tests are indicated if certain arthritides are suspected. These might include: rheumatoid factor, antinuclear factor (ANF), extractable nuclear antigen, and specific antibodies. Osteoarthritis Osteoarthritis is the most common form of arthritis. It affects humans and other animals, notably dogs, but also occurs in cats and horses. It can affect both the larger and the smaller joints of the body. In humans, this includes the hands, wrists, feet, back, hip, and knee. In dogs, this includes the elbow, hip, stifle (knee), shoulder, and back. The disease is essentially one acquired from daily wear and tear of the joint; however, osteoarthritis can also occur as a result of injury. Osteoarthritis begins in the cartilage and eventually causes the two opposing bones to erode into each other. The condition starts with minor pain during physical activity, but soon the pain can be continuous and even occur while in a state of rest. The pain can be debilitating and prevent one from doing some activities. In dogs, this pain can significantly affect quality of life and may include difficulty going up and down stairs, struggling to get up after lying down, trouble walking on slick floors, being unable to hop in and out of vehicles, difficulty jumping on and off furniture, and behavioral changes (e.g., aggression, difficulty squatting to toilet). Osteoarthritis typically affects the weight-bearing joints, such as the back, knee and hip. Unlike rheumatoid arthritis, osteoarthritis is most commonly a disease