Matthew C. DeLaney
CLINICAL FEATURES
Identifying the disorder as monoarticular or polyar-ticular can help narrow the differential diagnosis (Table 182-1).
Disorders with a migratory distribution include gono coccal arthritis, acute rheumatic fever, Lyme disease, viral arthritis, and systemic lupus erythematous.
The most concerning diagnosis is septic arthritis, and all decision making should involve confirming or excluding this diagnosis.
Obtaining and examining synovial fluid is the most important aspect of the workup of an affected joint. The clinician should be familiar with standard approaches to joint aspiration (Figs. 182-1 to 182-3).
TABLE 182-1 Classification of Arthritis by Number of Affected Joints
FIG. 182-1. Arthrocentesis of the shoulder, posterior approach.
FIG. 182-2. Arthrocentesis of the elbow.
FIG. 182-3. Arthrocentesis of the knee, lateral approach.
SEPTIC ARTHRITIS
In an acutely tender, warm joint with restricted range of motion, bacterial non-gonococcal septic arthritis is the most concerning diagnosis and must be ruled out.
Resistance to movement and a limited range of motion are notable findings. Constitutional symptoms (eg, chills and rigors) may be absent.
The peripheral white blood cell count lacks sensitivity and specificity in both adults and children with septic arthritis.
The erythrocyte sedimentation rate has a sensitivity of 96% using a cutoff of 30 mm/h, but has a poor specificity.
In septic arthritis, synovial fluid analysis usually reveals cloudy yellow fluid with a white blood cell count greater than 25,000 WBC/mL, and cultures that are positive more than 50% of the time (Table 182-2).
Patients with ongoing concern for septic arthritis after clinical evaluation require admission to the hospital for parenteral antibiotics and orthopedic consultation for possible surgical drainage.
Antibiotic coverage, typically involving vancomycin and a third-generation cephalosporin, should target staphylococcal and streptococcal species, including methicillin-resistant Staphylococcus organisms.
Specific patient demographics can help guide empiric antibiotic therapy in septic arthritis (Table 182-3).
GONOCOCCAL ARTHRITIS
Gonococcal arthritis is the most common cause of septic arthritis in adolescents and young adults, and typically features a prodromal phase of fever, chills, and migratory arthralgias or tenosynovitis followed by a monarthritis.
Vesiculopustular lesions may be present distal to the involved joint.
Synovial fluid cultures are often negative. Cultures of the posterior pharynx, urethra, cervix, and rectum may increase the yield of isolating the organism.
CRYSTAL-INDUCED SYNOVITIS
Gout, caused by uric acid crystal deposition, is the most common cause of inflammatory joint disease in men over the age of 40 years, and typically affects the great toe or knee.
Gout or pseudogout may be precipitated by trauma, surgery, significant illness, or a change in medication.
TABLE 182-2 Examination of Synovial Fluid
TABLE 182-3 Commonly Encountered Organisms in Septic Arthritis in Adolescents and Adults*
Identifying crystals in synovial fluid through a polarizing microscope is an important aspect of diagnosing both gout and pseudogout.
Uric acid (gout) crystals appear needle shaped and blue with negative birefringence, while calcium pyro-phosphate (pseudogout) crystals are rhomboid shaped and yellow with positive birefringence.
Up to 30% of patients with acute gout will have normal serum uric acid levels making this test of little utility in diagnosing gout.
Acute treatment for patients with adequate renal function is with nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or indomethacin. Opioid analgesia may also be required.
Colchicine can be prescribed at 0.6 milligram/h orally until efficacy ensues or the patient experiences the intolerable side effects of vomiting or diarrhea.
VIRAL ARTHRITIS
Parvovirus B19, rubella, and hepatitis B are the most common types of viral arthritis.
In adults, parvovirus B19 has polyarticular symptoms similar to acute rheumatoid arthritis.
Hepatitis B commonly involves the knee joint and can feature fevers, lymphadenopathy, and jaundice.
Fifty percent of females with acute rubella develop a polyarticular arthritis soon after developing the classic rash.
LYME ARTHRITIS
Lyme arthritis manifests as a monoarticular or symmetric oligoarticular arthritis, primarily affecting the large joints.
Lyme arthritis occurs weeks to years after a primary, Stage I infection of Lyme disease.
History of a tick bite or erythema migrans rash is often absent.
Synovial fluid cultures are usually negative and treatment is often based on clinical suspicion.
Treatment of Lyme arthritis consists of 3 to 4 weeks of doxycycline, penicillin, amoxicillin, or ceftriaxone.
TRAUMATIC HEMARTHROSIS
Hemarthrosis has a high association with intraarticu-lar fracture and ligamentous injury.
Spontaneous hemarthrosis should prompt an investigation for a coagulopathy
RHEUMATOID ARTHRITIS
Rheumatoid arthritis is a chronic, progressive, polyarticular synovial joint disease that affects women more frequently than men.
This disease is associated with stiffness after periods of inactivity, or “morning stiffness.”
Articular involvement is noted for symmetric, painful, tender joints, with sparing of the distal inter-phalangeal joints.
Acute exacerbations are managed with NSAIDs and brief courses of corticosteroids. Disease-modifying antirheumatic agents are used for long-term therapy.
OSTEOARTHRITIS
Osteoarthritis is notable for chronic, polyarticular exacerbations that lack the constitutional symptoms of rheumatoid arthritis.
The distal interphalangeal joint space is commonly involved.
Radiographs may show joint space narrowing.
Acute pain is treated with NSAIDs and resting the affected joint.
REITER’S SYNDROME
Reiter’s syndrome is a seronegative spondyloarthrop-athy that manifests as an acute, asymmetric oligoar-thritis with a predilection for the lower extremities that may be preceded 2 to 6 weeks earlier by an infectious illness, usually urethritis (Ureaplasma or Chlamydia) or enteritis (Salmonella or Shigella).
The classic triad of urethritis, conjunctivitis, and arthritis is not mandatory for diagnosis.
NSAIDs should be used for analgesia. Antibiotics have no proven benefit.
ANKYLOSING SPONDYLITIS
Ankylosing spondylitis is a seronegative spondyloar-thropathy primarily affecting the spine and pelvis that is characterized by morning stiffness in individuals <40 years old, with symptoms lasting more than 3 months.
Classic radiographic findings include sacroiliitis and squaring of the vertebral bodies (eg, bamboo spine).
Joint pain should be treated symptomatically with NSAIDs.
TABLE 182-4 Characteristics of Bursal Fluid in Patients with Septic and Nonseptic Olecranon and Prepatellar Bursitis
BURSITIS
Bursitis is an inflammatory process involving any bursae. It can be caused by infection, trauma, rheu-matologic disorders, or crystal deposition, or be idiopathic in nature.
Commonly affected bursae include the prepatellar bursa (eg, carpet layer’s knee) and the olecranon bursa.
Septic and aseptic bursitis cannot reliably be differentiated by physical examination alone, so aspiration of bursal fluid is required for cell count and differential, Gram’s stain, and culture.
Septic bursal fluid characteristically is purulent in appearance, with greater than 30,000 white blood cells/mL and is usually culture positive (Table 182-4).
Treatment entails resting the affected joint, analgesics, and antistaphylococcal antibiotics for 10 to 14 days if there is evidence of infection.
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 281, “Acute Disorders of the Joints and Bursae,” by John H. Burton.