II. Definitions

  1. Acute Monoarthritis
    1. Acute single joint inflammation developing in <2 weeks

III. Pitfalls

  1. Septic Joint
    1. Septic Arthritis is a rheumatologic emergency
      1. Infection may destroy a joint in 48 hours
      2. Mortality is as high as 7 to 20%, especially in advanced age
    2. Septic Arthritis presentations may be subtle (no fever, no erythema)
      1. Consider Septic Arthritis in any patient with painful, significantly limited joint range of motion
    3. Arthrocentesis is the only absolutely reliable method to exclude Septic Joint
      1. No blood test (including elevated Uric Acid level or normal WBC Count, CRP) excludes Septic Arthritis
      2. Chronically deranged joint is higher risk for Septic Arthritis (differentiate Septic Joint from acute exacerbation)
    4. Do NOT start antibiotics prior to Arthrocentesis, and DO initiate antibiotics afterward if findings suggest
      1. See exceptions under management below (e.g. Septic Shock)

IV. Causes: Common Monoarticular (Mnemonic: SINGL JOINT)

  1. Septic Arthritis (most important to rule-out)
    1. Bacterial Arthritis
    2. Fungal Arthritis
    3. Parasitic Arthritis
    4. Gonococcal Arthritis (esp. young sexually active adults)
    5. Mycobacteria
  2. Internal derangement
    1. Meniscus Injury
    2. Ligament tears
    3. Overuse syndromes
  3. Inflammatory Arthritis - Aseptic (e.g. Spondyloarthropathy, Reactive Arthritis)
  4. Neuropathy (Charcot's Joint)
  5. Gout, Pseudogout and other crystal-induced Arthritis
  6. Lyme Disease
  7. Juvenile or adult Rheumatoid Arthritis
  8. Osteoarthritis
  9. Osteomyelitis
  10. Ischemic bone (avascular necrosis)
  11. Neoplasms
    1. Osteoid Osteoma
    2. Pigmented Villonodular synovitis
    3. Bony metastases
  12. Trauma
    1. Overuse injury
    2. Fractures
    3. Hemarthrosis

VI. History

  1. See Joint Pain
  2. Predisposing factors
    1. Pre-existing Osteoarthritis or Rheumatoid Arthritis
      1. Septic Arthritis
    2. Prolonged Corticosteroid use
      1. Septic Arthritis
      2. Avascular necrosis
    3. Tick Bite
      1. Lyme Disease
    4. IV Drug Abuse, Immunodepression
      1. Septic Arthritis
  3. Timing of pain and swelling
    1. Extremely rapid onset within minutes
      1. Traumatic Arthritis (e.g. Fracture)
    2. Onset over hours to days
      1. Septic Arthritis
      2. Crystal Arthritis (e.g. gout)
    3. Onset over weeks to months
      1. Systemic Rheumatic disease
      2. Indolent infection
      3. Osteoarthritis
      4. Tumor
    4. Chronic or Long-standing
      1. Aggravated Osteoarthritis
      2. Crystal Arthritis
  4. Mediating factors
    1. Worsens with activity and improves with rest
      1. Mechanical cause (Trauma, Osteoarthritis)
    2. Morning Stiffness and worse with rest
      1. Inflammatory Arthritis (e.g. Rheumatoid Arthritis)
  5. Location
    1. Migratory
      1. Gonococcal Arthritis (Gonorrhea) initially migratory, but later affects primary joint)
      2. Rheumatic Fever
    2. Consider multiple joint involvement
      1. Oligoarthritis (<=4 joints)
      2. Polyarthritis

VII. History: Extraarticular Symptoms

  1. See Joint Pain
  2. See Differential Diagnosis below

VIII. Symptoms

  1. See Joint Pain
  2. Joint Pain and swelling

IX. Signs

  1. Joint effusion
    1. Most specific sign of intraarticular process and joint inflammation
  2. Distinguish articular from periarticular conditions
    1. Bursitis
    2. Fracture
    3. Tendonitis
  3. Range of motion
    1. Consider Septic Arthritis in any patient with painful, significantly limited joint range of motion
    2. Active range of motion limitation
      1. Periarticular problems
    3. Both Passive AND Active range of motion limitation
      1. Articular problems
  4. Normal joint exam
    1. Referred pain
  5. Palpation
    1. Swelling and pain
  6. Stress Pain (pain at extreme range of motion)
    1. Most sensitive sign of joint inflammation
  7. Examine all joints
    1. Assess for Polyarthritis
  8. Skin exam
    1. Psoriatic Plaque, Nail Pitting or Dactylitis
    2. Overlying Cellulitis or Septic Bursitis
    3. Skin Desquamation over joint (Gouty Arthritis)
    4. Erythema Nodosum (Sarcoidosis, Inflammatory Bowel Disease)
    5. Erythema over joint
      1. Infection (Cellulitis, Septic Bursitis, Septic Joint)
      2. Crystal Arthritis (e.g. Gouty Arthritis)

X. Labs

  1. See Joint Pain
  2. Arthrocentesis
    1. Single most important test to consider (critical if possible Septic Joint)

XI. Imaging

  1. See Joint Pain
  2. Plain film XRay
    1. Indicated for Trauma or focal bone pain
    2. Acute findings include Fracture or avulsion
    3. Subacute findings include Osteomyelitis or malignancy
    4. Chronic findings seen in Osteoarthritis, Rheumatoid Arthritis, or Gouty Arthritis

XII. Differential Diagnosis

  1. Septic Arthritis
    1. See Pitfalls above (most important to exclude)
    2. Risks include prosthetic joints, joint surgery, RA, CKD, DM, IVDA, Skin Infection, age over 80 years old
    3. Includes Gonococcal Arthritis (esp. sexually active young patients)
  2. Osteoarthritis
    1. Asymmetric Joint Pain and stiffness in the hands, spine, knees and hips
    2. Brief morning stiffness (<30 min), and Joint Pain after activity
    3. Heberden's Node (DIP), Bouchard's Node (PIP) are pathognomonic (1st MCP is commonly affected)
  3. Gouty Arthritis
    1. Thiazide Diuretics, Purines and Trauma may trigger gouty attacks
    2. Rapidly developing red, swollen joints (esp. 1st MTP)
    3. With chronic gout, tophi destroy joints
    4. Renal stones may form
  4. Behcet Syndrome
    1. Oral Ulcers
  5. Reiter's Syndrome
    1. Urethritis
    2. Conjunctivitis
    3. Diarrhea
    4. Rash
  6. Psoriatic Arthritis
    1. Psoriasis
    2. Nail Pitting
    3. Dactylitis (sausage-like swelling of digits)
  7. Ankylosing Spondylitis
    1. Uveitis
    2. Low Back Pain
  8. Sarcoidosis
    1. Hilar Adenopathy
    2. Erythema Nodosum
  9. Gonococcal Arthritis
    1. Young adults with high risk sex history
    2. Urethral discharge or Dysuria (Pharyngitis may also be present)
    3. Migratory polyarthralgias at onset, then settles in a single joint
    4. Tenosynovitis of hands and feet
    5. Pustules
  10. Hemarthrosis (Coagulopathy)
    1. Bleeding tendency
    2. Anticoagulant use
  11. Avascular Necrosis
    1. Systemic Lupus Erythematosus
    2. Corticosteroid use
    3. Alcohol Abuse

XIII. References

  1. Mann and Papp (2022) Crit Dec Emerg Med 36(17): 22-8
  2. Becker (2016) Am Fam Physician 94(10):810-6 [PubMed]

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