An orthopedic measurement system is disclosed to measure leg alignment. The measurement system includes a tri-axial gyroscope configured to measure movement of a leg. The gyroscope is coupled to a tibia of the leg. For example, the gyroscope can be placed in an insert or tibial prosthetic component that couples to the tibia. The gyroscope is used to measure alignment relative to the mechanical axis of the leg. The leg alignment measurement is performed by putting the leg through a first leg movement and a second leg movement. The gyroscope outputs angular velocities on the axes the sensor is rotated about. The gyroscope is coupled to a computer that calculates the alignment of the leg relative to the mechanical axis from the gyroscope measurement data.