The Centers for Disease Control and Prevention has stated that as many as 1 in 2 people in the United States may develop knee arthritis by the age of 85. In fact, it's been estimated that total knee replacement surgery will grow 673% by 2030. It's also been suggested that by age 25, as much as 14% of adults have arthritis that can be diagnosed via x-ray. There seems to be a connection between previous trauma and increased risk of knee arthritis as well. Meaning, those of you who have already had a sports or other injury to your knee could have increased chance of developing knee arthritis. Some common symptoms include pain with standing, walking, or stairs. Pain or stiffness after prolonged periods of sitting or standing. Noises such as grinding, popping, or cracking. Swelling is sometimes seen as well. There may be pain if you push on the inside and outside of knee, in the spaces between the bones of your legs.