Rheumatoid arthritis and osteoarthritis: Pathology review

A 65-year-old man comes to his primary care provider for evaluation of pain in both knees. His symptoms worsen with activity and improve with rest and ibuprofen. The patient had previously been an avid runner but had to stop due to the joint pain. Past medical history is notable for hypertension and a right fibular fracture, which occurred after a biking accident. Vitals are within normal limits. Examination of the affected joints reveals crepitus and mildly reduced range of motion. The remainder of the patient’s physical examination is noncontributory. Knee imaging is ordered, and the results are as follows:




Reproduced from: Radiopedia

Which of the following additional findings, if present, would best support the patient’s diagnosis?