DefinitionOsteoarthritis (OA) is the most common joint disorder.Alternative NamesHypertrophic osteoarthritis; Osteoarthrosis; Degenerative joint disease; DJD; OA; Arthritis - osteoarthritisCauses, incidence, and risk factorsIn osteoarthritis, the cushioning (cartilage) between the bones wears away in the joints. As osteoarthritis gets worse, the cartilage disappears and bone rubs on bone. Bony spurs or growths usually form around the joint. The ligaments and muscles around the joint loosen and become weaker.Often, the cause of OA is unknown. It is mainly related to aging, but other factors can also lead to OA.Osteoarthritis tends to run in familiesBeing overweight increases the riskFractures or other joint injuries can lead to osteoarthritis later in lifeLong-term overuse at work or in spo