A 45-year-old male presents with a 5-day history of
dysuria, increased frequency of micturition and discharge per urethra. He also
complains of a painful swollen right knee of one-day duration. He feels unwell
and has fever.
He works as a sales representative and has recently been
on a business trip to Amsterdam. He admits to having unprotected sex with a
prostitute. He smokes 10 cigarettes a day and consumes 30 units of alcohol per
On examination he is febrile pulse 90 beats per minute
blood pressure 130/80 heart sounds normal with no added sounds, respiratory
system no abnormity detectable, abdomen normal. His right knee is swollen,
there is evidence of an effusion and range of movement is restricted.
In this patient which of the following investigations
would be the most appropriate immediate investigation that will enable you to
reach a diagnosis?
Urethral smear for gram stain
Aspiration of knee with gram stain
X-ray sacro-iliac joints
X-ray of knee