Basic Approach to Joint Pain

GENERAL PRINCIPLES

• The first step is to differentiate between arthritis versus periarthritis. Arthritis is any process affecting a joint or joints, causing pain, swelling, and stiffness.

• The second step is to categorize arthritis as inflammatory or noninflammatory. This will depend on the pattern of joint involvement and the evidence of inflammatory findings on joint exam. Features of inflammatory arthritis include swelling, erythema, warmth over the joint, as well as the presence of prolonged morning stiffness of more than 1 hour that worsens with inactivity. Associated symptoms such as fever, weight loss, skin rashes, uveitis, scleritis, mouth ulcers, and serositis, among others, may give clues to an underlying systemic connective tissue disease (CTD).

DIAGNOSIS

Arthritis can be approached by the number, pattern, and acuity of joint involvement (Figure 25-1).

Ancillary Tests

• Laboratory tests and imaging are helpful in supporting a diagnosis if their use is directed by the specific findings on the history and physical examination. Laboratory evidence of inflammation may be helpful although not specific. These include erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and synovial fluid analysis.

• Arthrocentesis should be performed in all patients with acute monoarthritis.

TABLE 25-1

SYNOVIAL FLUID ANALYSIS

Important Factors for Synovial Fluid Interpretation

• Septic arthritis is associated with white blood cell counts gt;20,000 and frequently gt;50,000. The cutoff is no longer 50,000 due to lowered sensitivity, 50%-70%, although the specificity is high, 80%-90%.¹ The chances of septic arthritis increase as counts increase. Counts of lt;20,000 may be observed in disseminated gonococcal infection.

• Monosodium urate: sensitivity 63%-78%, specificity 93%-100%. Calcium pyrophosphate dihydrate crystals: sensitivity 12%-83%, specificity 78%-96%. The presence of crystals does not exclude infection.

• Gram stain should be performed but sensitivity is low. A negative Gram stain does not rule out an infection.

TREATMENT

Therapeutic approaches involve either local or systemic administration of analgesic, anti-inflammatory, immunomodulatory, or immunosuppressive drugs. This will be reviewed in each section.