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Many mechanisms provoke acute joint symptoms: degradation and
degeneration of articular cartilage (osteoarthritis), deposition
of immune complexes or immune system–related phenomena
(rheumatoid arthritis, rheumatic fever, and, possibly, a component
of gonococcal arthritis), crystal-induced inflammation (gout and
pseudogout), seronegative spondyloarthropathies (ankylosing spondylitis—primarily
genetic, and reactive arthritis—postinfectious with HLA-B27
susceptibility), and bacterial invasion (gonococcal and nongonococcal
septic arthritis, including Lyme arthritis), or viral invasion (viral
arthritis). These processes impact joint capsules and surfaces,
resulting in a cascade of reactive and inflammatory events. The
term septic arthritis refers to the invasion of
a joint by an infectious agent with proliferation and associated
inflammation; bacterial arthritis is a subset of septic arthritis.
Under ideal conditions, the infectious agent is recoverable from
the joint fluid in septic arthritis, but in practice, this may not
occur. This chapter reviews the common causes and treatments of
acute nontraumatic joint pain. Joint injuries are discussed in Section
22, Injuries to Bones and Joints, and disorders due to repetitive
use syndromes are discussed in Section 23, Musculoskeletal Disorders,
by anatomic site.
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Clinical Features
and Risk Factors
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The first step in diagnosis is distinguishing monoarticular from
polyarticular arthritis (Table 281-1) and
determining if joint pain is migratory or not (Table
281-2).1 The most concerning diagnosis
of acute joint pain is septic arthritis due to bacterial invasion,
so decision making focuses on its exclusion or inclusion. The
two most important diagnostic considerations for acute nontraumatic
monoarthritis are nongonococcal or gonococcal septic arthritis contrasted
with crystal-induced arthropathy (gout and pseudogout). Patient
age, gender, and comorbid illnesses are aids to diagnosis. Risk
factors for nongonococcal and gonococcal septic arthritis are listed
in Table 281-3.2–4Figure 281-1 provides a diagnostic algorithm
for the nontraumatic, acute monoarticular arthritis.
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