Systems, methods and a sensor alignment mechanism are disclosed for medical navigational guidance systems. In one example, a system to make sterile a non-sterile optical sensor for use in navigational guidance during surgery includes a sterile drape having an optically transparent window to drape the optical sensor in a sterile barrier and a sensor alignment mechanism. The alignment mechanism secures the sensor through the drape in alignment with the window without breaching the sterile barrier and facilitates adjustment of the orientation of the optical sensor. The optical sensor may be aligned to view a surgical site when the alignment mechanism, assembled with the sterile drape and optical sensor, is attached to a bone. The alignment mechanism may be a lockable ball joint and facilitate orientation of the sensor in at least two degrees of freedom. A quick connect mechanism may couple the alignment mechanism to the bone.