A 82-year-old man presents with pain and swelling of his right knee for 1 year, resulting in difficulty in walking. He also noticed a mass in the same knee 6 months ago, which has gradually increased in size over time. He was diagnosed with type 2 diabetes mellitus 10 years ago, which is currently well controlled. An HbA1C last month was 5.5%. His surgical and family histories are unremarkable. He does not smoke or use recreational drugs, but drinks socially.