The Philadelphia 76ers are withholding center Andrew Bynum from basketball activities for three weeks for precautionary reasons, the team announced Monday. Bynum received Orthokine therapy for his bruised right knee in September. Bynum came to Philadelphia as part of the four-team Dwight Howard trade in August. He averaged 18.7 points and 11.8 rebounds in 60 games last season for the Los Angeles Lakers. The Sixers begin training camp Tuesday at St. Joseph's University. The team also signed free agent center Mikki Moore, bringing their roster up to 18 players. The 13-year veteran has averaged 5.8 points and 3.9 rebounds in 18.2 minutes per game while shooting 55.1 percent for his career.