Question: A 19-year-old man consulted for a 24-hour history of pain, swelling and functional impotence of the right knee accompanied by a fever of 38ºC. Physical examination reveals inflammatory signs and joint effusion in the right knee. The analytical data show a leukocytosis with neutrophilia and an elevation of the C-reactive protein. The syndromic diagnosis of acute monoarthritis is made. What is the most likely etiologic diagnosis? 
 Options:  <1> Arthritis by microcrystals. <2> Reactive arthritis <3> Bacterial infectious arthritis. <4> Infectious arthritis due to mycobacteria. <5> Rheumatoid arthritis.
3