Fetlock

[Sarah]

The cushionlike projection, bearing a tuft of long hair, on theback side of the leg above the hoof of the horse and similar animals.Also, the joint of the limb at this point (between the great pasternbone and the metacarpus), or the tuft of hair.Their wounded steeds Fret fetlock deep in gore. Shak.

[Rihanna]

The joint of a horse

[Dave Paprocki]

Fetlock in Harness Racing. Lowest joint on a horses leg.

[Tanya Shivari]

the part of a horses leg at the back, just above the foot, where longer hair grows