|Muggles' Guide to Harry Potter - Magic|
|First Appearance||Harry Potter and the Philosopher's Stone|
Locomotor Mortis is the "leg-locker" curse. Similar in effect to the body bind, this spell causes only the legs to be bound together.
We see this spell used only a very few times. Draco Malfoy uses it on Neville in Harry Potter and the Philosopher's Stone, though that is done off-stage and we only hear about it from Neville after he manages to hop into the Gryffindor Common Room.
This spell is of limited utility as it leaves the target's wand arm free, so that he can either free himself or retaliate. It is likely to be useful only on a disarmed opponent or one without developed magical abilities. As such, it is probably a classic first-year sort of jinx, one that impedes the opponent but does not harm him particularly.