Osteoarthritis (degenerative arthritis, degenerative joint disease) is a chronic joint disease characterized by degeneration of joint cartilage and adjacent bone, eventually causing joint pain and stiffness. Osteoarthritis is the most common joint disorder and can affect people to varying degrees by age 70. The incidence is essentially the same in men and women, but the age of onset is earlier in men. Osteoarthritis can occur in almost all vertebrates such as fish, amphibians and birds. Aquatic animals such as dolphins and whales are no exception. However, two animals that often hang limbs – bats and sloths – do not suffer from this disease. The disease is so widespread in the animal kingdom that many authorities believe that osteoarthritis may involve an ancient method of repairing joint cartilage. Many myths about osteoarthritis persist, and just as hair turns gray and skin wrinkles, aging is inevitable and there is nothing humans can do about it, nor is there a magic bullet. Although osteoarthritis is common in the elderly, it is not simply caused by age and wear and tear. Many patients, especially younger people, have few symptoms. However, many older adults experience significant functional impairment. Under normal circumstances, there is little friction between joints to cause wear and tear, unless there is overuse or injury. The most likely cause of osteoarthritis is an abnormality in the components of synthetic cartilage, such as collagen (a tough, fibrous protein in connective tissue) and mucin (a substance that produces cartilage elasticity). In addition, cartilage, although growing vigorously, is thin and its surface is prone to rupture. Bone overgrowth at the edges of the joints forms visible and palpable masses (called osteophytes). Osteochondrosis causes unevenness of the joint surface, interfering with the normal joint function and causing pain. All of the above causes the moist, smooth cartilage surface to become rough and uneven, and the joint does not move smoothly. All joint components – bone, joint capsule (the tissue that surrounds the joint), synovium (the tissue lining the joint capsule), tendons and cartilage – lose their normal function and form to varying degrees, changing the structure of the joint. Osteoarthritis of unknown etiology is called primary (idiopathic) osteoarthritis. Secondary osteoarthritis is called secondary osteoarthritis if it is caused by deformational osteoarthritis, infection, deformity, injury, or overuse of the joint. People who repeatedly strain their joints are at high risk of developing osteoarthritis, such as foundry workers, miners and bus drivers. However, long-distance runners are not at high risk for this disease. Obesity is a major contributor to osteoarthritis, but the evidence is not yet strong. Many people in their 40s will have some signs of osteoarthritis on X-rays, especially in weight-bearing joints such as the hip, but are usually asymptomatic. Usually, symptoms occur slowly and affect one or more joints first. The finger joints, base of the thumb, neck, low back, toes, hip and knee are common sites of involvement. Pain is the first symptom and can be aggravated by exercise. Some people feel stiffness after waking up from sleep or after being at rest for a long time, but the stiffness gradually disappears within 30 minutes of moving the joint. When osteoarthritis causes severe damage, the joint cannot move and is fixed in flexion. New cartilage, bone and other tissues thicken the joint, and the rough cartilage can cause wear and tear on the joint surface during joint movement. Osteophytes (Hebden’s nodes) are usually found at the ends of the finger joints. In some joints, such as the knee, the ligaments that surround the joint and keep it stable become loose, making the knee unstable and causing severe pain when the joint is touched or moved. In contrast, the hip joint becomes more rigid, loses its normal range of motion, and still feels painful when moving. Osteoarthritis often affects the spine. Back pain is a common symptom. Involved joints can cause mild pain and stiffness. However , osteoarthritis in the neck or low back can produce symptoms such as numbness, abnormal sensation, pain and limb weakness if the overgrowth of bone compresses the nerves. Less commonly, osteophytes can compress the blood vessels supplying the back of the brain, causing visual impairment, vertigo, nausea, and vomiting. The growth may also compress the esophagus and cause difficulty swallowing. Osteoarthritis often continues to progress slowly after the onset of symptoms, and many people experience varying degrees of functional impairment. Occasionally, degeneration of the joint will stop on its own or even tend to improve. This helps to preserve healthy cartilage, increase the range of motion of the joint, and strengthen the muscles around the joint so that they can better absorb shocks. Exercise must be balanced with other painful joints. Inactive joints are more likely to aggravate osteoarthritis than active joints. The use of excessively soft seats, pillows, mattresses and car seat cushions can aggravate existing symptoms. The use of straight-backed chairs, hard mattresses and bedpans is recommended. Specialized exercise is beneficial for osteoarthritis of the spine. When the condition is severe, a back brace or bandage may be used. It is important for the patient to maintain daily activities and to be independent in the roles they play in the home and at work in order to treat the disease. Physical therapy, usually using heat, is beneficial for the disease. For example, paraffin wax mixed with mineral oil is heated to 47.8 to 52.2 °C, and then the affected hand is placed in a paraffin bath. Patients with painful fingers can also use warm water baths. Splints or braces may be used to protect specific areas of the joint during periods of active pain. When a specific type of osteoarthritis involves the cervical spine, massage, traction, and deep heat therapy with diathermy or ultrasound can be useful for relief. Medications are secondary to the overall treatment plan. Sometimes pain medications such as acetaminophen may be used. Non-steroidal anti-inflammatory drugs such as aspirin or ibuprofen may relieve pain and swelling. When a joint becomes suddenly inflamed, swollen, and painful, a corticosteroid may be injected directly into the joint to treat the pain. Surgery may be considered when other treatments fail to relieve symptoms. Arthroplasty of the hip and knee is highly effective and can significantly improve joint function, increase joint motion, and reduce pain after surgery. Therefore, joint replacement surgery should be considered when joint function is significantly impaired.