Final answer:
Joint stiffness with aging is mainly due to changes in the articular cartilage, often leading to osteoarthritis. This condition results from "wear and tear" of the cartilage, which causes pain, swelling, and reduced joint mobility.
Step-by-step explanation:
The joint stiffness that occurs with aging is typically due to changes in the articular cartilage that covers the ends of bones at a synovial joint. Osteoarthritis, the most common type of arthritis, is associated with the "wear and tear" of articular cartilage. As the cartilage wears down, the joint responds by producing more lubricating synovial fluid, which can cause swelling and pain, leading to joint stiffness. Risk factors for developing osteoarthritis include joint injury, physically demanding jobs, certain sports, and being overweight. Treatments for osteoarthritis aim to alleviate pain and may include lifestyle changes like weight loss and low-impact exercise, medication, and in severe cases, joint replacement surgery.