Joint pain is a very common problem with many possible causes - but it's usually a result of injury or arthritis.
1. Pain in just one joint like knee joint. It can be due to osteoarthritis. It is quite common in older people but it can sometimes affect younger people, especially those who are overweight or those who have had serious injuries to the joint in the past.
2. Pain in many joints, most commonly the hands, feet and wrists. It can be due to rheumatoid arthritis, psoriatic arthritis, viral infection that causes arthritis.
The knee joint is particularly vulnerable to damage and pain because it takes the full weight of your body