Osteoarthritis is mostly caused by wear and tear of ageing process, but excessive weight, extreme physical activity, or repetitive manual tasks can make it worse. The exact cause of Osteoarthritis is unknown, but it is often linked to genetic predispositions and injuries to the joint. Inflammation of the joint, diet, and damage to the bone underneath the cartilage which supplies the cartilage with nutrition all contribute to the degenerative changes of osteoarthritis.