My 18 yr old son had knee surgery on Aug 1. He has been losing weight ever since, for a total of about 20 lbs. He s 6 2 , and normally weighs about 190. (now, 170) This seems drastic to me. When I began to notice the loss, I watched and monitored him. He is eating plenty of nutritious food, he should actually be gaining weight, but he is not. I will make a doc appt tomorrow, but I m curious what might cause this. Thank you!