Obesity or local inflammation of a joint is also closely associated. If OA is indeed the end result of any joint injury, nearly any possible cause may be valid. However, recent studies point to a genetic predisposition. In a few people, OA appears in x-rays as early as the teenage years. Aging is certainly a factor, and it may be true that in different people the cartilage simply wears out at different ages.
Nothing is forever.
We know that the appearance of OA is more frequent as we get older. Trauma may be as important a cause as genetics and aging. We know that a blow to a joint from an athletic injury, for example, can produce pain and changes many years after the main injury occurred. Similarly, it can be argued that OA of the fingers is often due to a life of repeated-motion injury, as in women who work in weaving factories. We also know that impact injury is an important cause of damage to cartilage.