Nature, Causes, and Epidemiology of Musculoskeletal Conditions
Osteoarthritis is the most common condition affecting human joints and causes significant disability. The principal clinical features are pain, which varies in severity and character, and stiffness. Disability occurs as a result of pain, weakness, joint instability, and reduced range of motion.
The following are the major forms of inflammatory arthritis:
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rheumatoid arthritis
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seronegative spondyloarthropathies
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ankylosing spondylitis
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reactive arthritis
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enteropathic arthritis
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psoriatic arthritis
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juvenile chronic arthritis
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systemic
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pauciarticular
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polyarticular
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arthritis associated with systemic connective tissue diseases
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systemic lupus erythematosus
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progressive systemic sclerosis
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vasculitis
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polydermatomyositis
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crystal arthritis
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gout
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calcium pyrophosphate deposition disease
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RA has a prevalence of between 1 and 3 percent in most countries for which figures are available, but it may be slightly less common in tropical countries. The exact etiology of RA is unknown, but the evidence suggests an immune reaction, and it presents as an inflammation affecting joints and other tissues. Its clinical features can be divided into three groups: constitutional, articular, and extraarticular. Constitutional features involve tiredness, fatigue, weight loss, and fever, and articular features involve principally the synovial joints, producing pain and eventual deformity and disability.
The seronegative spondyloarthropathies are primarily inflammatory arthropathies and share several common features, including familial aggregation, asymmetric joint involvement, and mucocutaneous lesions. These conditions may follow gastrointestinal or sexually acquired infections and can be associated with HIV. Gout and other forms of crystal arthritis tend to present as an inflammatory response to the presence of uric acid (gout) or various calcium crystals (chondrocalcinosis).
Much of the pain that produces complaints and reduced function does not emanate from a frank arthropathy, but from the soft tissues in or around a joint. When these pains are confined to a particular area of the body's surface, they can be referred to as regional pain syndromes and may or may not be related to injury or overuse. If these pains are more widespread and are associated with specific tender points, the condition is known as fibromyalgia. Fibromyalgia is well recognized in the industrial world and has also been noted in China and Malaysia and among Tamil Indians.
The major causes of infectious arthritis can be viral, bacterial, fungal, or helminthic. Each can present as either a polyarticular presentation or a monarthritis. Many of the helminthic infections present with more generalized aches and pains and involvement of muscle tissues as well as joints. All the conditions have specific diagnostic features and treatments.
OP is characterized by low bone mass and deterioration in the microarchitecture of the bone, which leads to fracture after low or moderate trauma. The condition is defined by diagnostic criteria based on bone mineral density as follows: a bone mineral density of more than -2.5 standard deviations below the average bone mineral density of young adult women.
The clinical features of OP are primarily due to its major outcome: fracture. The most important fractures occur in the distal radius, vertebrae, or hip, often following minor trauma. Vertebral fractures lead to loss of height, kyphosis, and back pain. The incidence of fracture varies with country and with type of fracture. Hip fractures are low in African countries but high and increasingly reported in Australasia, Europe, and North America. Fracture risk increases with age and is beginning to have a significant impact on quality of life, mortality, and health care costs in many countries.
Rickets is caused by a mineralization defect of newly formed bone in the growing skeleton. This defect leads to an increase in the amount of nonmineralized bone tissue (osteoid) and a thinning of the growth plates. This condition produces bone pain, bone deformation, swelling of the joints, and growth retardation. Rickets is primarily caused by a lack of exposure to sunshine because of climate, pollution, or overuse of clothing or sunscreens. Rickets is relatively rare in industrial countries, but it does occur as a consequence of dietary deficiency or excess clothing.
Osteomalacia is the adult equivalent of rickets. It is similarly characterized by an increase in osteoid tissue and causes bone pain and fractures. It occurs primarily in the elderly in Europe and North America because of a lack of exposure to sunshine that is not compensated for by adequate vitamin D intake. Osteomalacia may also occur in countries with abundant sunshine where clothing prevents sun exposure. Osteomalacia is commonly reported among migrants to Western Europe from India and the Middle East.
Back pain accounts for the majority of musculoskeletal disease presentations to health professionals, and its lifetime prevalence exceeds 80 percent in most industrial countries. Spinal disorder refers to a wide range of specific and nonspecific musculoskeletal disorders affecting the spinal column. These conditions include congenital lesions such as scoliosis, infective problems such as osteomyelitis and neoplastic disorder (myeloma or secondary cancers), and trauma and referred back pain.
The majority of individuals with acute back pain will improve significantly over a six-week period, although in many cases the pain may recur. Early diagnosis and treatment, particularly of pain, by means of a modified exercise program will reduce long-term morbidity and disability.
Musculoskeletal injuries are extremely common, whether in the workplace or associated with sporting activities or with daily living. Motor vehicle trauma, household accidents, and occupational accidents occur frequently and are a major cause of damage to the musculoskeletal system.
Table 51.3 shows the major genetic and environmental risk factors for musculoskeletal diseases. Lack of exercise and obesity are major contributors to soft tissue disorders, OA, and back pain. Infectious forms of musculoskeletal disease depend on the environment and on the types of organisms that are prevalent.
[Table .]
