There are several reasons to see a doctor. If you have swelling in your knee, it can represent an underlying problem that may not go away on its own. Pain that does not improve with rest. If you have redness, fever, and chills, you should see your doctor urgently to rule out an infection.
You will likely need an x-ray and sometimes an MRI to further evaluate your knee. Your doctor may provide you with a brace, injections or medications to treat your pain. If necessary, an orthopedic surgeon can help you determine if you need surgery.