A 21-year-old male presents with intermittent back pain for 1 year, worse at night and upon waking, and unexplained left knee joint swelling and pain for the past week. This patient should be highly suspected of having:
A 21-year-old male presents with intermittent back pain for 1 year, worse at night and upon waking, and unexplained left knee joint swelling and pain for the past week. This patient should be highly suspected of having: