Sure they can. In addition, sometime the fetlock strain can be cause by the horse taking a wonky step due to weak stifles. You should look into a good rehab program as long as your vet doesn't think there's anything pathological going on.
I also suggest getting an ultrasound to check for tendon damage as it can effect how you rehab; and good diagnosis allows for best possible long term prognosis :)
The one time I had a horse with what really was a fetlock sprain, it resolved very quicky with cold hosing and wrapping. There was no on again off again lameness, he just came in one day with a swollen fetlock, and was quite lame. I think it was literally two days, and he was back to normal.
Personally, I'd be tempted to spring for an ultrasound to check for tendon damage if it was my horse. But I'll admit, I'm a worrier :)