My husband was diagnosed with carcenoma in the salvary glands on both sides of his neck in Jan 2008. He has undergone four - week long stays in the hospital for chemo. He was told in early April 2008 that the cancer is in remission now. But since he has been out of the hospital -he has been experiencing a weakness in his knees. He will stumble when walking several times a day. What could this symptom indicate? He says he is not light headed when this happens - just a weakness in the knees.