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What causes bone spurs to form in osteoarthritis?

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In osteoarthritis, bone spurs—also known as osteophytes—form as a result of the body’s attempt to repair damage caused by the progressive deterioration of articular cartilage.12

As the protective cartilage wears away, the underlying subchondral bone is left exposed to increased stress and mechanical forces. In response to this damage, the bone attempts to regenerate the lost tissue, which leads to increased bone density and an uneven remodeling of the joint surface. During this process, masses of newly proliferated bone protrude from the margins of the joints, forming the characteristic thick bony outgrowths known as spurs. These developments are often driven by biomechanical factors, such as faulty mechanical loading or repetitive microtrauma, which trigger the body's local bone repair mechanisms.123