This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology and Rheumatology, Subject name: Medicine
A 72-year-old man injures his right knee in a car accident, and now it is swollen and extremely painful to bend the knee. X-rays of the knee rule out a fracture, and joint fluid aspiration reveals an opaque-colored fluid containing rhomboid crystals with weak-positive birefringence. Which of the following is the most appropriate next step in management? 
Select and explain. 
A. oral prednisone, B. intravenous antibiotics, C. oral NSAIDs, D. acetaminophen
C: oral NSAIDs
Answer: C: oral NSAIDs 
Explanation: In traumatic arthritis, swellings, ecchymoses, muscular spasms, and tenderness tend to be present, but fractures must be excluded. This man has calcium pyrophosphate (CPPD) crystal-induced monoarthritis, so called "pseudogout." It is most common in the elderly and can be precipitated by minor trauma. The crystals have a rhomboid shape, and the clinical presentation can mimic that of gout. It can be associated with metabolic abnormalities such as hyperparathyroidism or hemochromatosis. Treatment is with an NSAID for 7-10 days. If there are multiple joints involved, then steroids can be considered. An alternative to oral NSAIDs is intra-articular steroids for single joint disease. Allopurinol is not effective in CPPD. Synovial fluid is bloody, but the fluid is of normal viscosity, so a "string" test is usually positive.