Arthritis

Osteoarthritis

Osteoarthritis is the most common form of arthritis, affecting nearly one-third of people over the age of 65. As the population ages, so will the number of people affected by osteoarthritis—59 million cases are expected by 2020. Also known as degenerative joint disease, osteoarthritis is characterized by joint pain and mild inflammation due to deterioration of the articular cartilage that normally cushions joints. Joint pain is gradual in onset, occurring after prolonged activity, and is typically deep and achy in nature. One or multiple joints may be affected, predominantly involving the knee, hips, spine, and fingers.

Approximately 90 percent of individuals experience crackling noises (crepitus) in the affected joint with motion. Muscle weakness and joint laxity or stiffness can occur as people become reluctant to move painful joints. Patients tend to have decreased joint stability and are predisposed to injuries such as meniscal [Page 162]and anterior cruciate ligament tears. Hip arthritis can affect gait, while arthritis of the hands can lead to decreased dexterity. Enlargement of the bony processes surrounding affected joints, called osteophytes (bone spurs), are common.

Joint trauma, increased age, obesity, certain genetic components and occupations, and hobbies or sports that result in excessive joint stresses can result in the cartilaginous changes leading to osteoarthritis. Damage begins with the development of small cracks in the cartilage that are perpendicular to the joint. Eventually, cartilage erodes and breaks off, facilitating painful bone-on-bone contact. In due course, pathologic bony changes, such as osteophytes and subchondral bone cysts, develop and further restrict joint movement and integrity.

Osteoarthritis may be divided into two types, primary and secondary osteoarthritis. Primary osteoarthritis is age-related, affecting 85 percent of individuals 75–79 years of age. Although the etiology is unknown, primary osteoarthritis is associated with decreased water retaining capacity in the cartilage, analogous to a dried-up rubber band that can easily fall apart. Secondary osteoarthritis is caused by another condition, such as joint trauma, congenital joint malalignment, obesity, hormonal disorders, and osteonecrosis. In addition, treatment for osteoarthritis is directed toward reducing pain and correcting joint mechanics, and may include exercise, weight loss, nonsteroidal anti-inflammatory drugs, steroids, and total joint replacement surgery.

Autoimmune Arthritis

Autoimmune arthritis is characterized by joint inflammation and destruction caused by one's own immune system. Genetic predisposition and inciting factors, such as an infection or trauma, can trigger the inappropriate immune response. Rheumatoid arthritis is often associated with elevations in the serum level of an autoantibody called rheumatoid factor, whereas the seronegative arthropathies are not.

Rheumatoid arthritis is a progressive inflammatory condition that can lead to decreased mobility and joint deformities. The worldwide prevalence is 0.8 percent, with a 3:1 predilection for women over men. Disease onset, mainly occurring in the third and fourth decades of life, may be acute or slowly progressive with initial symptoms of fatigue, weakness, malaise, weight loss, and mild, diffuse joint pain. Rheumatoid arthritis tends to affect the hips, knees, elbows, ankles, spine, hands, and feet symmetrically. The disease course is characterized by periods of remission, followed by progressive exacerbations in which specific joints become warm, swollen, and painful. Morning stiffness, typically lasting about two hours, is a hallmark feature of rheumatoid arthritis. Patients with rheumatoid arthritis tend to complain of joint pain after prolonged periods of inactivity, whereas osteoarthritis is typically exacerbated with extended activity. Rheumatoid arthritis can be severely debilitating, resulting in a variety of deformities. Complete remission is reported in less than 10 percent of patients and typically occurs within two years of onset.

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