Question category: Rheumatology
A 58 year old male presents with pain in his MCPs bilaterally, his ankles, wrists and knees. He is stiff for 3 hours in the morning. He has lost some weight. Bloods reveal raised inflammatory markers and a normochromic, normocytic anaemia. Rheumatoid factor and ANA are negative and a CK is 175. Which of of the following is the most likely diagnosis?