This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology and Rheumatology, Subject name: Medicine
A 74-year-old woman has pain in her right hand and lower back, which started months ago, and is now interfering with her activities of daily living. The pain gets worse as the day progresses. There is no history of any trauma, and she is otherwise well. Taking over-the-counter acetaminophen usually relieves the pain. On examination, there is bony soft tissue swelling of her second and third DIP joints in the right hand and pain in her lower back on forward flexion. There is no erythema or joint effusion in any of the other joints. Which of the following is the most likely explanation for the joint pain of osteoarthritis? 
Select and explain. 
A. synovial inflammation is not the cause, B. ligament inflammation is a common cause, C. clinically visible (via plain x-ray) fractures are a common cause of pain, D. osteophytes can cause pain
D: osteophytes can cause pain
Answer: D: osteophytes can cause pain 
Explanation: Osteophytes can cause pain by stretching periosteal nerve endings. Synovial inflammation is frequently seen in osteoarthritis, but not in ligament inflammation. Microfractures, but not macro-fractures, commonly cause pain. Muscle spasm can be an important factor in the joint pain.