lymph nodes in neck

I work in Radiology and three days ago I was rubbing my neck and felt a small bump. Our ultrasound technologist took a look and said it appears to be a lymph node about .8 cm in diameter and appeared normal. I have found four more about the same size around the back of my head along the hairline and near my ears as well. Since that day, they have become more noticable, and the first one I found is now actually visible from the side. My concern is that I had mildly invasive surgery on my right knee last Spring and am still having swelling and pain in the joint. Could this be related to that surgery? I believe it's most likely a new infectious response to something, in that cancer would not likely develop and advance so fast. What could this possibly be? Could it be cancer even though the lymph tissue appeared normal? I am a white male age 33 with no current health problems. Thanks in advance.

[J.M. Keyes, MD]

Hi there,
The most likely explanation is an ENT type infection, as those lymph nodes would be draining the areas from your neck up.  You would more likely have issues with lymph nodes behind your knee (popliteal) or in your groin (inguinal) related to an infection in the knee.  If you think you could actually have an infection in your knee (red/hot/fever/swelling/pain) your must see your MD urgently.  
Your description does not sound like malignancy, however there is no way to tell without a complete history and physical exam.  A needle biopsy is the most conclusive test if there is a concern about malignancy (cancer), rather than ultrasound, so if you have no current respiratory/ear/sinus/tooth/throat etc infection that could be explaining this, you should see your doctor to at least be examined.  Even if you do have a current infection that could be explaing your enlarged nodes, you must follow up with your MD if they are not resolving, or are getting worse.
Best of luck,
JMK MD