A surgical guidance system (1) for orthoscopic drilling is disclosed which comprises a probe (10), the end (12) of which is suitable for locating on the emergence site of a hole to be drilled through body tissue, a targeter (20) comprising one or more sensors for locating the position of the probe (10), a drilling guide (21), and a control system (30) in communication with the targeter (20) for collating the position of the probe (10) measured by the targeter (10) and providing a real-time visual representation (31) of the relationship between the direction of the drilling guide (21) and the end of the probe (12) to allow the user to align the drilling guide (21) to the end of the probe (12). The probe (21) comprises an elongate shaft (13) and one or more, preferably two or more, elements (11) located at physically separated positions along the shaft (13), and wherein further the elements (11) can be detected by the targeter (20) and are each positioned at locations removed from the end of the probe (12).
