Bent the knees is a common phrase used to describe the action of flexing or bending one's knees. However, there are many synonyms that can be used to convey this action. Some alternatives include: crouched down, kneeled, squatted, hunkered, bowed, bowed down, stooped, or ducked. These synonyms can be used to add variety and depth to writing, making it more interesting and engaging for the reader. Depending on the context of the sentence, some synonyms may be more appropriate than others. Overall, there are many different ways to describe the act of bending one's knees, and choosing the right synonym can help to paint a vivid picture in the reader's mind.