Described within are systems, methods and apparatus for a bone mounted robotic-assisted orthopedic surgery system for precise implant position, soft tissue balancing and guidance of tools during a surgical procedure, particularly partial or total knee replacement procedure. The system features a bone mounted robotic arm with end-effector for precise positioning of surgical tool, positioning of implants and balancing of soft tissues. The reconfigurable robotic system requires minimal training by surgeons, is intuitive to use similar to conventional instrumented surgery and has a small footprint. The system works with existing, conventional instruments, patient specific instruments, sensor-assisted systems and computer-assisted systems and does not require increased surgical time and safely provides the enhanced precision achievable by robotic-assisted systems and computer-assisted technologies.