Ben has been a long distance runner his whole life. He has run in fifteen marathons and countless smaller road races. When he turned 75, he started feeling pain and a loss of movement. He went to see a physician who said that he had a wearing-away of cartilage and his joints have become less flexible and prone to swelling. Which condition is Ben diagnosed with?

A) osteoarthritis
B) rheumatoid arthritis
C) osteoporosis
D) Parkinson's disease

Ben's symptoms are consistent with osteoarthritis, a condition where the cartilage in joints wears away, leading to pain, stiffness, and swelling. Rheumatoid arthritis is an autoimmune disease that affects the joints and can lead to joint damage, but it typically affects younger people and causes different symptoms. Osteoporosis is a condition where bones become weaker and more brittle, which can lead to fractures, but it does not typically cause joint pain or swelling. Parkinson's disease is a neurological disorder that affects movement and can cause tremors, rigidity, and difficulty with coordination, but it is not associated with joint problems.