Black Haired Girl Plays With Apples And Reveals Her Blue Skirt And Over-the-knee Socks

Most sports will require some sort of sock, usually a tube sock to protect one's legs from being scraped while participating in sport activities. In basketball, tube socks are worn, and in lacrosse, mid-calf socks are required.
Other uses
The layer of leather or other material covering the insole of a shoe is also referred to as a sock. When only part of the insole is covered, leaving the forepart visible, this is known as a half-sock.