Knee arthritis can also be called osteoarthritis. Osteoarthritis is often the result of increased strain on the joint due to weight, or repeated injury or damage. Knee arthritis is definitely more common in middle aged to elderly persons. There are less related methods of testing for knee arthritis as well. The main one is simply a blood test- doctor's will be able to see deficiency in the blood results. An arthroscopy will also most certainly confirm the diagnosis of knee arthritis, however this will only be recommended if there is an intention to fix the knee arthritis.