Assessment of patients with acute joint pain.
Is the Patient Systemically Ill?
Whenever a patient with acute joint pain also presents with fever, rigors, systemic symptoms, or signs of involvement of additional organ systems, careful evaluation is necessary to rule out potentially life-threatening processes such as infection or diffuse vasculitis. Hospitalization and consultation for evaluation of rheumatic or infectious disease are usually required for patients with arthritis and systemic symptoms. Obtain blood cultures, and perform the evaluation outlined below.
Is This Disseminated Gonococcal Infection?
In young adults, hematogenous gonococcal infection is one of the most common causes of acute arthritis. Arthritis may be the sole manifestation of disseminated gonococcal infection. Skin lesions are few and are found on the extremities, frequently around a joint, and are pustular or hemorrhagic, rarely bullous. Gram-stained smears of material contained in the pustules may reveal gram-negative diplococci within polymorphonu-clear neutrophils. Tenosynovitis classically involves tendons of the hand or foot. The primary (mucosal) site of gonococcal infection is often asymptomatic. If disseminated gonococcal infection is suspected, culture of blood and secretions from the pharynx, rectum, and urethra or cervix should be obtained.
Is There Arthritis on Joint Examination?
Ascertain by careful examination whether acute joint pain is due to an intra-articular process. Is there redness, diffuse warmth, effusion, or painful limitation of active and passive motion? If the joint is not involved, consider cellulitis, tenosynovitis, bursitis, or other periarticular lesions.
Is the Process Oligoarticular or Polyarticular?
Involvement of 1–3 joints in an asymmetric pattern is generally considered a characteristic of oligoarthritis, although this asymmetric involvement may occur early in some polyarticular conditions such as juvenile rheumatoid arthritis. Common causes of oligoarthritis include infection, crystal deposition (eg, gout), and trauma. The polyarthritis syndromes involve many joints, usually in a symmetric fashion.
If one of the affected joints is acrally located (eg, wrist, elbow, knee, ankle), arthrocentesis should be attempted in the emergency department, using local anesthesia and sterile technique (Chapter 6). A specialist and/or ultrasound guidance should be considered for arthrocentesis of the shoulders and hips. The joint fluid should be analyzed and the results should be used to classify the arthritis according to the scheme in Table 19–1.
Classification of Arthritis
Table 21–1. Classification of Abnormal Synovial Fluid.
| Save Table
Table 21–1. Classification of Abnormal Synovial Fluid.
|Type of Joint Fluid||Viscosity||Clarity||Color||Leukocyte Count (per μL)||Gram Stain and Culture||Other Findings|
|Noninflammatory (class I)||High||Clear||Light yellow||<4000||Negative||…|
|Inflammatory (class II)||Low||Cloudy||Dark yellow||>2000–<50,000||Negative||Crystals are diagnostic of gout or pseudogout (differentiate with polarizing microscopy); usually seen with class II joint fluid|
|Septic (class III)||Low||Cloudy||Dark yellow||Usually > 50,000||Usually positivea||Bacteria on culture or Gram-stained smear. Usually seen with class III joint fluid but may be seen with class II; rarely, class I|
|Hemorrhagic (class IV)||Variable||Cloudy||Pink-red||Usually > 2000b||Negative||Fat globules strongly suggest intraarticular fracture and are usually seen with class IV joint fluid|
Noninflammatory (Class I)
Acute arthritis in the presence of normal joint fluid usually indicates trauma, or osteoarthritis. Rarely, early joint aspiration in inflammatory arthritis produces a similar result.
Inflammatory arthritis may be present in acute gout, pseudogout, Reiter syndrome, rheumatoid arthritis, and rheumatic fever. Gram stain and culture of synovial fluid should be done to rule out early infectious arthritis.
Purulent joint fluid (class III) is seen almost exclusively in bacterial and fungal infections. Gram stain of joint fluid may help to identify the causative organism before cultures become positive.
Hemorrhagic joint fluid is seen in trauma with or without fracture; the presence of fat globules suggests fracture. A tear in the anterior cruciate ligament is the most common cause of hemarthrosis in the knee when no fracture is present. Other frequent causes of hemarthrosis include peripheral meniscus tears and patellar dislocations (with medial retinaculum tears). Hemorrhagic effusion is more likely to be associated with acute pain than is the noninflammatory effusion that can occur with minor joint trauma, because blood within the joint space generally causes an inflammatory reaction. Hemorrhagic fluid is also seen in hemophilia and in synovial neoplasms.
1This chapter is a revision of the chapter by Terry C. Hermance and L. Richard Boggs, from the 6th edition.
Monarthritis or Oligoarthritis
- Effusions often develop immediately after trauma
- Fever or other systemic signs or symptoms are not present
Severe joint pain associated with trauma is usually related temporally to an obvious injury. Mild pain may occur some time after the injury. Fever and other systemic signs usually are not present. The presence of noninflammatory or hemorrhagic synovial fluid confirms the diagnosis. Because patients with septic arthritis may also give a history of recent trauma, Gram stain and culture of fluid routinely should be performed.
The presence of many small fat globules in hemorrhagic joint fluid strongly suggests intra-articular fracture; X-rays should be carefully scrutinized ...