A surgical instrument which can be attached to a patient is described. The instrument includes an alignment guide having a distal end and a proximal end. A brace is attached toward the proximal end of the alignment guide for attaching the instrument to a limb of a patient. The brace comprises a pair of opposed members, each member being shaped to hold a respective bony part of the patient on either side of the patient. At least a part of the brace is made of a resilient material allowing the brace to grip the patient in use.
