My classmate Alex P. suggested that I do a week of "pseudo" cases. Here we go!
A 65 year old man presents to your office complaining of severe pain and swelling in his left knee. He's had these symptoms 2-3 times in the past but they resolved without medical attention. On exam, you notice a red, hot, swollen left knee. Here's a radiograph:
You tap the knee. The synovial fluid has 20,000 leukocytes, 90% neutrophils. You examine it under compensated polarized microscopy:
Challenge: What do you think?
First image shown under GNU Free Documentation License; second image shown under Fair Use.