How do I judge my knee pain. Surgery or arthritis?

Structure v function. I agree that a thorough work up is needed. Even if you do have arthritis, it may or may not be the source of your pain. Even if it is, there are many treatments that may restore your function without the need for surgery. See a physiatrist, sports med doc, or orthopedist for evaluation.
Not too fast. Just because you have joint pain does not mean arthritis and does not mean surgery. You have to have the knee evaluated. Many times the knee pain is not arthritis but it could be bursitis or tendonitis. Sometimes you can have knee pain but the origin is not the knee, it is the hip. You will need an examination, imaging like x-rays, ultrasound, MRI and even joint fluid examine.