Dallas Mavericks star Dirk Nowitzki will be out at least six weeks after having arthroscopic surgery Friday on his right knee, the team announced. Nowitzki, 34, can resume on-court activities within that time frame, in which the Mavericks have 13 regular-season games scheduled. Nowitzki has missed the Mavericks' last three preseason games with swelling and soreness in the knee. He hoped to delay the surgery, but doctors determined it was needed sooner to alleviate the cause of the inflammation. Nowitzki had the knee drained twice this month, but the swelling returned both times. His knee also didn't respond to rest, icing and low-impact conditioning.