It sounds like your knee pain is probably affecting your quality of life. For these reasons you should probably consider seeing a doctor
soon. It is difficult to tell from your description what might be causing your knee pain. One of the most common causes of knee pain is osteoarthritis, but this is not necessarily the cause in you especially if you are young. If you are older, say in your 50s or older, then osteoarthritis or wear and tear arthritis could be a cause of your symptoms. In younger people, there are many other causes of knee pain such as tendinitis, meniscal tears, and other causes of inflammation of the joint itself. For starters, you should schedule an appointment with an orthopedic surgeon
. The surgeon will perform a physical exam of your knee and probably determine the cause just from that. If he or she is unable to determine the cause from the physical exam, then they will likely obtain plain x-rays of the knee. If the x-rays are unremarkable, and the cause of your knee pain is not known, then you will need to get an MRI
of the knee to find out if there is a fixable problem. In addition, if there is no physical problem, at the very least you can get recommendations for medications that you take for the pain in addition to physical therapy.