Bursitis Workup

Updated: Oct 16, 2023
  • Author: Jonathan D Hendrie, MD; Chief Editor: Herbert S Diamond, MD  more...
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Blood Studies

Routine laboratory blood work is generally not helpful in the diagnosis of noninfectious bursitis. In cases of septic bursitis, however, the leukocyte count and erythrocyte sedimentation rate (ESR) may be mildly to moderately elevated. Blood cultures may be drawn if infection of deep bursae is a concern. ESR, antinuclear antibody (ANA), rheumatoid factor (RF), and anti–citric citrullinated peptide (anti-CCP) tests should all be ordered in cases where autoimmune disease is suspected, because these inflammatory disorders can trigger bursitis.


Joint Aspiration and Fluid Analysis

Aspiration and analysis of bursal fluid should be done to rule out infectious or rheumatic causes; they may also be therapeutic. Bursal fluid should be sent for crystal analysis, cell count with differential, gram stain, and aerobic/anaerobic bacterial culture. Fungal and mycobacterial testing should be sent if there is suggestive history or clinical suspicion. Physicians should be more inclined to perform bursal fluid aspiration in the most frequently infected bursae—the olecranon (see the image below), prepatellar, and infrapatellar bursae.

Olecranon bursitis: aspiration of hemorrhagic effu Olecranon bursitis: aspiration of hemorrhagic effusion. Image courtesy of UMDNJ-New Jersey Medical School, www.DoctorFoye.com, and www.TailboneDoctor.com.

Nonseptic bursitis has cell counts lower than 2000/µL, with a predominance of mononuclear cells. Septic bursitis may have cell counts exceeding 70,000/µL, with a predominance of polymorphonuclear leukocytes (PMNs). The white blood cell (WBC) count in septic bursitis is typically lower than that in septic arthritis. A WBC count of 5000-20,000/µL or higher may be considered indicative of infection.

Gram stain and culture are performed to identify any pathogens. These results can guide the modification of antibiotics in cases of bacterial infection. The most common organism cultured is the gram-positive coccus penicillinase-producing Staphylococcus aureus. [23]

The accuracy of Gram staining varies considerably, with sensitivities between 15-100%. Therefore, fluid that has a high WBC count but negative Gram stain is still suspicious for infection and should be managed accordingly.

Elevated protein level and reduced glucose level (or a low bursal-to-serum glucose ratio) are associated with infection but are not sufficiently sensitive or specific to be used in isolation. Bursal fluid culture is the conclusive test for diagnosis. Culture in liquid medium has been shown to be superior to culture on solid medium. [30]

With chronic or recurrent bursitis, samples should be sent for acid-fast staining and cultured on special media for mycobacteria, fungi, algae, and Brucella.

Fluid should also be examined for crystals. Monosodium urate crystals are seen in gout; calcium pyrophosphate crystals are seen in pseudogout; cholesterol crystals are seen in rheumatoid chylous bursitis and in a variety of chronic effusions.

Arthrocentesis should be performed if joint involvement is suspected.


Plain Radiography, Bone Scanning, MRI, and CT

Plain radiography usually is not helpful in the diagnosis of bursitis but may be useful for identifying underlying bony pathology (eg, fractures, arthritis, osteophytes, or dislocations) that may trigger bursal inflammation. They may also show joint effusions. In chronic bursitis, the bursal walls or nearby tendons may be calcified and radiopaque.

Bone scanning is not a sensitive test for bursitis, but it may be done in cases in which the diagnosis is unclear to rule out other causes of pain.

Because of the characteristic clinical presentation of bursitis, magnetic resonance imaging (MRI) and computed tomography (CT) are usually unnecessary. MRI can be useful for delineating the anatomy of the entire joint (including adjacent soft tissues) and depicting bursal or prebursal fluid and associated abscesses [31] ; if needed, it is a very sensitive test for identification of bursitis. MRI is also helpful in ruling out suspected solid tumors and defining pathology for possible surgical excision.



Ultrasonography is useful for further imaging of the bursa when the diagnosis is uncertain. For diagnostic aspiration or treatment injections, ultrasonography may be performed to elucidate the structures and to guide procedures. The accuracy of ultrasound-guided injections has increased; however, studies of the efficacy of ultrasound-guided versus blinded injections provide variable results. [32, 33] In addition, ultrasound studies distinguish solid from cystic masses and are helpful in detecting Baker cysts (popliteal bursitis) when there are extensive joint deformities. [12, 34] Baker cysts are often discovered incidentally when lower-extremity Doppler studies are done to rule out deep vein thrombosis.