You're not describing a sweep. You're describing a kick. A kick with the intention of removing support, but a kick and not a sweep.
How would I be totally wrong about foot sweeps?
A perfect judo foot sweep coming from behind the leg won't put much strain on the leg. However, foot sweeps are also done in striking arts. In my opinion, those sweeps usually resemble a low kick to the side of your lower leg. That does put strain on your knees. If you throw a roundhouse which I catch. I then kick your lower leg, below the knee. That's what usually is thrown as a sweep in savate, kickboxing.. That puts a lot of strain on the knees.