It is worth having this looked at by your primary care doctor
to make sure nothing serious is going on.
The most likely possibility is that you have evolving osteoarthritis
, which is "wear and tear" or age-related arthritis. This is the type of arthritis that is caused by aging and breakdown of the cartilage in the major joints, and it is initially treated by modifying your type of exercise (avoiding high impact exercise), ice, and anti inflammatory medicines like ibuprofen or naprosyn.
Another possibility would be patello femoral pain syndrome, which occurs when the patella does not track well over the femur, leading to some breakdown of the cartilage in the patella. It often is characterized by pain that is worse with bending the knee, and it is more common in people with arch problems. You may need to make sure that the orthotic you are wearing is the appropriate one that prevents over pronation. Also, leg strengthening exercises can be an important part of correcting this problem.
Rarely, this kind of pain can be from a joint infection. If you have fever
, increasing pain, or any redness or heat to the joint, you should see your doctor immediately.