It is not at all unusual to still have swelling two weeks after arthroscopic knee surgery. Since you did not mention an acute increasein pain and swelling, fever, chills, redness, or drainage, I assume they are not present, and therefore, I am less worried about infection.
I think two weeks post-op is premature to seek a second opinion. You should see your surgeon this week. At that time, he may drain your knee with a needle and syringe, start you on anti-inflammatory medication, inject your knee with cortisone, or alter your physical therapy regimen.
