A surgical instrument is described which comprises an alignment guide having a first part including a distal end and a second part having a proximal end. The first part is attached to the second part by a pivot mechanism so that the first part can be tilted relative to the second part. A brace is attached toward the proximal end of the alignment guide for attaching the instrument to a limb of a patient. A component is attached toward the distal end of the alignment guide. The pivot mechanism is configured so that tilting the first part does not substantially change the separation between the component and the brace.
