Ddx, most likely
     Flare-up of osteoarthritis
     Crystal arthritis
          Gout
          Pseudogout
     Bacterial arthritis
          Gonorrheal     
          Staphylococcal
Sx
     Calor, dolor, rubor, tumor
Workup     
     Aspirate
          Cell count w/diff
               Cloudy or particulate w/>50k WBC: septic
               >=50k WBC w/PMN predominance: may be inflammatory
               Gram stain  negative result does not r/o septic
          Fluid cx  may take >= 2d
          Microscopic exam for crystals: 
               Gout: uric acid crystals
               Pseudogout
                    Calcium pyrophosphate dehydrate crystals
                    Rhomboid-shaped
                    Positively-biregringent crystals
          Hemarthosis:  suspect coagulopathy if atraumatic
          If traumatic, fat droplets from bone marrow in aspirate indicates intraarticular bony fracture

Content on this page has not been checked for accuracy. The author's credentials have not been confirmed. Always use multiple peer-reviewed scholarly sources and good clinical judgement in your decision making.

The Compendium platform was created by David Kwinter, MD, CCFP(EM).

Dr. Kwinter is a Cayman Family Doctor. He runs a Family Medicine Clinic at Cayman Medical in George Town, Grand Cayman, Cayman Islands.