Did some googling on the subject and there does seem to be some debate on whether over the knee boots are apprpriate for the workplace. I would assume several factors come into play:
The type of business and the job
The clothes worn with the boots. Other site said a sheath would be fine but watch the length (also avoid looking like a pirate
They also said suede is more appropriate than leather.
It could be a generational thing. I'm pushing 50 and I wouldn't consider them appropriate
and frankly the wrong kind of professional garb (I could change my mind on seeing the actual outfit on someone.) Maybe younger people don't have the Julia Roberts bias.
To keep with the movie theme (because we all know life is exactly like the movies, right?
, there's a line from the movie, "The Devil Wears Prada" in which Andie Sachs (Anne Hathaway) says something like: "I don't need to change. Miranda (Priestly -- played by Meryl Streep) hired me. She knows what I look like."
Nigel (Stanley Tucci): "Do you
It took some doing but I can picture a grey tweed sheath with leather over-the-knee boots looking good. That is, when the person is standing up. Somehow I just can't picture it looking right when the person is sitting (cross-legged or not), bending over, kneeling down (to pick up a pencil etc.), reaching up. Perhaps the co-irker sees something, the wearer doesn't.
One last movie reference: "Working Girl" when Sigourney Weaver's character first hires Melanie Griffith's. She says something about professional, classic attire. Melanie Griffith (in full 80's poufy hair and skads of necklaces etc. -- like Madonna in her heyday) says, "How's this?" Sigourney Weaver says she's fine, "...but I'd rethink the jewelry." Perhaps, just perhaps, that's what the co-irker was trying to say. Or, she could be a shrew, granted.
ETA: To add a comment that I thought to add after I posted this. Sorry.