Arthritis, any of more than 100 different diseases causing pain, stiffness, and in most cases, swelling in the joints.Arthritis affects people of both sexes and of all races, socioeconomic levels, and geographic areas.Osteoarthritis is the most common type of knee arthritis. Also called wear-and-tear arthritis or degenerative joint disease, osteoarthritis is characterized by progressive wearing away of the cartilage of the joint. As the protective cartilage is worn away by knee arthritis, bare bone is exposed within the joint. Knee arthritis symptoms tend to progress as the condition worsens. What is interesting about knee arthritis is that symptoms do not always progress steadily with time. Often patients report good months and bad months or symptom changes with weather changes. This is important to understand because comparing the symptoms of arthritis on one particular day may not accurately represent the overall progression of the condition.The most common symptoms of knee arthritis are:pain with activities, limited range of motion, stiffness of the knee, swelling of the joint, tenderness along the joint, a feeling the joint may "give out", deformity of the joint (knock-knees or bow-legs). Rheumatologists, physicians who diagnose and treat arthritis and related conditions, use a variety of diagnostic techniques. The first step is a thorough history and physical examination, during which the doctor questions the patient about symptoms and medical history to learn about potential exposure to infectious agents or a family history of arthritis. The patient is examined to determine the pattern of joints affected. With this information, rheumatologists are usually able to make a diagnosis. Laboratory tests are used to help diagnose inflammatory arthritis. For example, a blood test called erythrocyte sedimentation rate measures how quickly red blood cells cling together and fall to the bottom of a test tube. When there is inflammation in the body, red blood cells sink faster. This test lets physicians evaluate how severe the inflammation is. Rheumatologists also test a patient’s blood or synovial fluid for the presence of specific antibodies—disease-fighting agents activated in the body by infections. The presence of rheumatoid factor antibodies, for example, is an indication of rheumatoid arthritis, and antinuclear antibodies can be an indication of lupus. The presence of these antibodies along with clinical symptoms help establish the diagnosis. Physicians may also elect to test for the presence of specific genes, such as the HLA-B27 gene. The primary goal of treatment is to reduce joint pain and inflammation and to maximize joint mobility. To this end, rheumatologists work closely with patients and their families to develop a treatment regimen incorporating exercise and rest as well as pain-relieving and anti-inflammatory drugs, and in some types of arthritis, drugs that slow the progress of the disease. Low impact, regular exercise is very important in maintaining muscle strength and joint mobility. One of the best forms of exercise for people with arthritis is swimming, an activity that lets participants use muscles with minimal joint strain. Arthritis sufferers benefit from physical therapy programs specially tailored to their age level and degree of mobility. Stretching and hot showers before exercise and applying ice packs to muscles and joints after exercise minimize discomfort related to exercise. Rest is another crucial element of arthritis treatment. In addition to recommending at least eight hours of sleep a night, rheumatologists may also advise patients to use a cane, splint, sling, or special footwear to rest or stabilize affected joints periodically during the day. Almost all drugs used to treat arthritis can have side effects and may not work for all patients with arthritis. Researchers are investigating alternatives to traditional drug therapy and other treatment approaches. If joint damage is severe, patients with arthritis may need to have surgical treatment. Total hip and total knee replacements can significantly relieve pain and improve joint function. In some cases, surgeons replace damaged or deteriorating joints with artificial stainless steel or plastic components in a procedure called arthroplasty.