Ankle boots would reach up just above the ankle and some boots extend the full length of the leg. These were typically for riding and were worn with spurs. Folding down the tops of these boots was quite common and give the distinctive shape to the 17th century bucket top boot.
Boots in the SCA
Many people in the SCA don't bother with period footwear, citing cost and safety as concerns. Many of those who do make themselves shoes which look period but are more comfortable than traditional designs.
Boots in Re-Enactment
Period boots are common in metal weapons groups and due to their popularity are often limited to only those who are portraying an individual who would likely have worn such (eg a knight or cavalry). In this case it is generally expected that the individual would display other aspects of the same portayal (eg spurs, appropriate clothing)). More common are ankle boots which were worn by many levels of society.