WASHINGTON, Jan 5 (Xinhua) -- Miami Heat coach Pat Riley underwent surgery on his right knee on Friday when pieces of cartilage were removed.

    The National Basketball Association team said the coach had three large pieces of cartilage that were causing him severe pain removed during the one-hour arthroscopic procedure.

    Riley, who also serves as team president, will also need to undergo hip surgery at a later date.

    Assistant Ron Rothstein has taken over as coach of the defending NBA champions in Riley's absence.