A number of factors can increase your risk of having knee problems. Certain types of knee problems are more common in young people, while arthritis tends to affect older adults, being overweight or obese increases stress on the knee joints, certain abnormalities, such as having one leg shorter than the other, lack of muscle flexibility or strength, certain sports(that put greater stress on the knees) and a previous knee injury makes it more likely to have knee pain again.
Attribution: Straight Talk Foundation