Surgical instrument

A surgical instrument for use in a knee-replacement operation, the surgical instrument comprising:

• a main body configured for releasable fastening on a tibia-cutting block for guiding cutting on a proximal tibia of a tibia;
• a first stylus;
• and
• a second stylus,
• the first stylus and the second stylus each being mounted on the main body so as to be movable relative to the main body,
• the first stylus and the second stylus each having a first end and a second end and extending along a longitudinal axis between the first end and the second end,
• the first ends each configured to make contact with a tibial plateau of the tibia,
• the first stylus being mounted on the main body so as to be pivotable about a first pivot axis relative to the main body and the second stylus, and
• the second stylus being mounted on the main body so as to be pivotable about a second pivot axis relative to the main body and the first stylus.