膝ひざを崩くずす

expression, godan verb (-su)

sit at ease; relax one's sitting posture

Used when shifting from a formal sitting posture (such as 正座) to a more relaxed position, often by uncrossing or stretching the legs. Implies a release of formality.

• どうぞ膝ひざを崩くずして楽らくにしてください。

  Please sit at ease and make yourself comfortable.

• 長ちょう時じ間かん正せい座ざしていたので、膝ひざを崩くずした。

  I had been sitting in seiza for a long time, so I relaxed my posture.