Osteoarthritis of the knee occurs in middle-aged and older people, usually over the age of 40. If your knee joint is swollen, painful, and has limited movement without obvious trauma, it can mean that something is definitely wrong with your knee joint. But what is wrong? Generally speaking, if you have recently gone hiking, or climbed stairs, or danced, or experienced knee pain after walking long distances, then you should be aware of this. This is often related to wear and tear of the cartilage in the joint, and it is likely that you have osteoarthritis in the knee. It is advisable to go to the hospital for a checkup, preferably with an X-ray. The normal knee gap is symmetrical. If the gap is wide on one side and narrow on the other, or even if the gap disappears, this is a clear indication that you have osteoarthritis of the knee. In other cases, if there is no obvious cause for the knee swelling and pain, it is important to rule out rheumatoid arthritis, gouty arthritis and other diseases, and to go to the hospital for laboratory tests.