Final answer:
Based on the presentation of acute knee pain, redness, fever, and fluctuance, along with a history of diabetes, the most likely diagnosis for this patient is septic arthritis. Gouty arthritis is less likely given the symptomatology and recent physical strain, and osteoarthritis or rheumatoid arthritis are also less likely based on the acute presentation and systemic signs of infection.
Step-by-step explanation:
The 67-year-old male with a history of type II diabetes presents with symptoms that include knee pain, redness, fever, and fluctuance over the patella following physical strain. These symptoms are commonly seen in septic arthritis. This condition is characterized by an infection within the joint, and the history of being on the knees for an extended period could have predisposed to a local bacterial introduction, particularly if there was any abrasion or minor injury.
Gouty arthritis usually affects the big toe, knee, or ankle, and although knee involvement is possible, the recent stress and symptoms align more closely with infection. Osteoarthritis typically involves chronic pain worsened with movement and without signs of systemic infection like fever. Rheumatoid arthritis, an autoimmune condition, generally presents with symmetrical joint involvement and other systemic features over a longer duration.
Considering the acute presentation, involvement of a single joint, fever, and fluctuance over the knee joint, along with the DMII which increases the risk for infections, the most likely diagnosis is septic arthritis, which requires urgent medical evaluation and treatment.