There are many synonyms for the phrase "bends the knees," including flexes the knees, crouches, squats, kneels, bows, stoops, and ducks. Each of these phrases can convey a slightly different movement or intent, from a quick crouch to avoid an obstacle to a deep bow as a sign of respect. Some of these phrases also have additional connotations, such as kneeling as a sign of deference or submission. Using different synonyms can add variety and depth to your writing or speech, while also allowing you to choose the specific word that best matches the situation or context.