Is writing "kneel down" redundant?

I've seen both "kneel" and "kneel down" writing.

When I enterd "kneel down" in the software After the Deadline, it says it's a redundant expression. Is that correct?

Example sentence:

I went over to the edge of the cliff and knelt down.


Yes, "kneel down" is redundant.

However, it is still grammatically accurate and widely used.