Is it valid to bend the knees during bowing (ruku')?

Question:
May Allah reward you. This questioner asks: Is it valid to bend the knees during bowing (ruku')?

Answer:
How does one bend the knees during bowing (ruku')? The knees are not bent except when sitting. As for bowing (ruku'), the knees are not bent, but one bends forward in bowing. Yes, bowing (ruku') is bending forward. As for bending them, that is only in prostration (sujud) and in sitting. Yes.