Plain radiograph, CT, MRI usually not helpful
US may help guide procedures or help with diagnostic uncertainty
Bursal fluid aspiration
Both diagnostic and therapeutic
Do not perform if there is evidence overlying cellulitis
Procedure
Placed in flexed position, elbow and forearm rested on surface
Prep and drap
Plus/minus local anesthesia skin wheal
Approach with 18-22 ga needle from posterior aspect of bursa, aspirate until bursa is flat
Compressing bursa to help with aspiration
Arthrocentesis should be performed if joint involvement suspected
Septic workup
Cell counts > 5000 - 20,000/µL depending on source
Predominance of PMNs
Cell counts < 2000/µL, with a predominant mononuclear cells highly suggestive of nonseptic bursitis
Gram stain and culture
Gram stain with variable levels of sensitivities
Thus, high WBC count with negative gram stain should not exclude diagnosis
Elevated protein
Reduced glucose
Crystal analysis
Both diagnostic and therapeutic
Do not perform if there is evidence overlying cellulitis
Placed in flexed position, elbow and forearm rested on surface
Prep and drap
Plus/minus local anesthesia skin wheal
Approach with 18-22 ga needle from posterior aspect of bursa, aspirate until bursa is flat
Compressing bursa to help with aspiration
Arthrocentesis should be performed if joint involvement suspected
Cell counts > 5000 - 20,000/µL depending on source
Predominance of PMNs
Cell counts < 2000/µL, with a predominant mononuclear cells highly suggestive of nonseptic bursitis
Gram stain and culture
Gram stain with variable levels of sensitivities
Thus, high WBC count with negative gram stain should not exclude diagnosis
Elevated protein
Reduced glucose
Crystal analysis
Predominance of PMNs
Cell counts < 2000/µL, with a predominant mononuclear cells highly suggestive of nonseptic bursitis
Gram stain with variable levels of sensitivities
Thus, high WBC count with negative gram stain should not exclude diagnosis
Septic bursitis
Olecranon bursitis 
Hip bursitis
Prepatellar bursitis 
Cellulitis
Calcaneal bursitis
Septic arthritis
Septic arthritis 