What gives bone a polished, "ivory-like" appearance in osteoarthritis?

In osteoarthritis, the polished, "ivory-like" appearance of bone is primarily attributed to eburnation. Eburnation occurs when the cartilage that normally covers the ends of bones in a joint wears away due to mechanical stress and degeneration. As the cartilage is lost, the underlying subchondral bone is exposed and subjected to increased friction and stress. Over time, this leads to a dense, smooth surface on the bone, which resembles ivory.

This process of eburnation not only results in the characteristic appearance but also indicates advanced joint degeneration. The smooth appearance is a result of the adaptive remodeling of bone in response to the loss of protective cartilage.

Other changes associated with osteoarthritis, such as osteophyte formation, subchondral cysts, and joint space narrowing, contribute to the pathology and clinical features of the disease but do not specifically create the polished appearance of the bone. Osteophytes are bony outgrowths that develop at the edges of joints, while subchondral cysts are fluid-filled sacs that can form beneath the cartilage. Joint space narrowing indicates loss of cartilage but does not address the appearance of the bone itself.