Bursitis is an inflammatory process involving one of the >150 bursae in the body, but most commonly the bursa overlying the elbow or the knee (see also chapter 281, "Hip and Knee Pain").37 Bursitis can be caused by repetitive trauma or can be associated with gout, pseudogout, or rheumatoid arthritis. Repetitive activities that can precipitate bursitis are identified by the typical names given: "carpet layer's or housemaid's knee" (prepatellar bursitis) or "student's elbow" (olecranon bursitis). The affected bursa is easily palpated but is not tender and not erythematous. Bursal enlargement is usually chronic or progressive but not acute. If bursitis is acute, consider septic bursitis (see "Septic Bursitis" below). In nonseptic bursitis, there is no limitation of, or pain upon, joint movement. The skin over the bursa may be thickened and calloused, indicating chronic repetitive trauma or pressure. Treatment is NSAIDs and elimination of activities that produce symptoms. Aspiration and drainage of bursal fluid is controversial (if infection is not suspected), because bursal fluid often reaccumulates after aspiration.
Unlike septic arthritis, septic bursitis is more likely secondary to bacterial spread from a skin lesion or local cellulitis to an injured or inflamed bursa. Therefore, cultures more closely reflect skin flora.37 Septic bursitis is characterized by acute pain, tenderness, erythema of the affected bursa, and overlying warmth when compared with the unaffected side.37,38 The most common sites for septic bursitis are the prepatellar bursa (50% to 53%) and the olecranon bursa (40% to 45%).38,39,40
Fever occurs in <50% of patients with septic bursitis.38 Pain can occasionally be mild (10%) but is usually moderate or severe.39 Associated cellulitis of the surrounding skin may be evident.
Most authors recommend the aspiration of bursal fluid if septic bursitis is considered.37,39 Bursal aspiration can be diagnostic and therapeutic. Bursal fluid demonstrates characteristic findings in infection (Table 284-7).37 Culture is the definitive test for presence or absence of infection. Diagnosis is presumed by one of the following criteria based on bursal fluid results: positive Gram stain, >3000 WBC/mm3, >50% polymorphonuclear cells, glucose <31 milligrams/dL, or bursal to serum glucose ratio of <50%.37
TABLE 284-7Characteristics of Bursal Fluid in Patients with Septic and Nonseptic Olecranon and Prepatellar Bursitis ||Download (.pdf) TABLE 284-7 Characteristics of Bursal Fluid in Patients with Septic and Nonseptic Olecranon and Prepatellar Bursitis
| ||Septic ||Traumatic and Idiopathic ||Crystal Induced |
|Appearance ||Purulent or serosanguineous ||Straw colored, serosanguineous, or bloody ||Straw colored to bloody |
|Leukocytes/mm3 ||Range, 350–392,000; mean, 54,3300 ± 34,197; >3000 is considered diagnostic ||Range, 0–11,700; mean, 2475 ± 1988 ||Range, 1000–6000; mean, 2900 |
|Differential count ||>50% polymorphonuclear cells is considered diagnostic ||Predominantly mononuclear ||Highly variable |
|Ratio of bursal fluid to serum glucose ||<50% in 90% of cases (diagnostic) ||>50%, 70%–80% in 98% of cases ||Unknown |
|Gram stain ||Positive in 70% (diagnostic) ||Negative ||Negative |
|Crystals present ||No* ||No ||Yes |
|Culture results ||Positive (diagnostic) ||Negative ||Negative |
S. aureus accounts for the majority of infections, but Staphylococcus epidermidis and Streptococcus species are also encountered.37,38,39 Septic bursitis generally responds well to oral antibiotics, with emphasis on coverage of Staphylococcus and Streptococcus species. With the high prevalence of methicillin-resistant S. aureus, adjust antibiotic choice according to local sensitivities. Conditions that require hospital admission for incision and debridement and IV antibiotics include sepsis, extensive purulent bursitis, extensive surrounding cellulitis, suspected joint involvement, immunocompromise, or failure to respond to a course of oral antibiotics.37 See specific treatment recommendations below.
The olecranon bursa overlies the olecranon process on the extensor surface of the elbow. The bursa is tense and edematous. Pain elicited with range of motion at the elbow is minor until the motion tightens and compresses the distended overlying bursa. Gouty tophi on the extensor surface of the elbow may be palpable or visible if the cause of bursitis is crystal-induced bursitis. If bursal fluid is aspirated, uric acid crystals are evident on microscopy.
To aspirate the olecranon bursa, prepare the bursal skin and use antiseptic technique. The patient's arm can be extended to allow for maximal bursal distention. Use a lateral approach to the affected bursa. Remove as much fluid as possible, and send the aspirate to the laboratory for analysis for WBC, Gram stain, crystals, glucose, and culture.
Treatment depends on patient condition; if septic, the patient should be treated with vancomycin, 15 milligrams/kg, plus piperacillin/tazobactam, 4.5 grams IV, or meropenem, 500–1000 milligrams IV. Most patients can be treated as outpatients with a 14-day course of oral antibiotics.37,38,39 Common antibiotics chosen include clindamycin, 300 milligrams three times per day for 10 days, or dicloxacillin, 500 milligrams four times per day.39 Trimethoprim-sulfamethoxazole is an alternative.38 Steroids are not indicated in the ED because infection cannot be definitively excluded by negative culture results. Admission is indicated for clinical toxicity, extensive surrounding cellulitis, failure of outpatient treatment, or immunocompromise. Some patients benefit from surgical excision of the bursa sac.40
Bursitis may affect any of the four bursae surrounding the extensor aspect of the knee (see Figure 281-6). A history of overuse or repetitive trauma to the prepatellar area is typical.37 The noninfected or aseptic bursa is enlarged and taut but nontender and not warm. There is full range of motion of the knee. If septic patellar bursitis is a consideration (Figure 284-12), aspirate the prepatellar bursa to obtain fluid for analysis. Prepare the skin overlying the bursa and use aseptic technique. Use either a lateral or medial approach. Fluid analysis and treatment are the same as for septic olecranon bursitis (see "Olecranon Bursitis" above).
Septic prepatellar bursitis. This patient presented with obvious purulence of his right prepatellar bursal sac. Aspiration confirmed septic bursitis. [Courtesy of Alan B. Storrow, MD. Reproduced with permission from Knoop K, Stack L, Storrow A, Thurman RJ: Atlas of Emergency Medicine, 3rd ed. © 2010, McGraw-Hill, New York.]