Skin surgery - the square knot

The square knot must be used in all cases, and is tied as follows:

• 2 slips forward so that the hands cross and the needle ends up away from the operator 
• 1 slip back so that the hands uncross and the needle ends up next to the operator
• 1 slip forward so the needle again ends away from the operator

When each knot is tied the suture should be gently ‘wriggled’ together as opposed to forcefully pulled together. Just enough tension should be used to oppose the skin edges but not too much that will strangulate the wound. For surface sutures the knots are tied across the wound, whereas with subcutaneous sutures the knots are tied along the wound.

For detailed information refer to the PCDS surgical guidelines.